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organised.",3,[37,169,328],{"id":38,"data":39,"type":25,"version":25,"maxContentLevel":35,"summaryPage":41,"introPage":49,"pages":56},"016d186f-e58e-4796-96ec-967774d9b4c0",{"type":25,"title":40},"Introduction to the Periodic Table",{"id":42,"data":43,"type":35,"maxContentLevel":35,"version":24},"ebd9ed02-28d9-42d4-9b29-fa5919a28e07",{"type":35,"summary":44},[45,46,47,48],"Elements are defined by the number of protons in their nucleus","The periodic table arranges elements by atomic number, not atomic weight","Mendeleev predicted undiscovered elements by leaving gaps in his table","Group 1 metals are highly reactive and good conductors due to their atomic structure",{"id":50,"data":51,"type":52,"maxContentLevel":35,"version":24},"d8609e01-e8b3-46e8-b8b8-04d6ae50d321",{"type":52,"intro":53},10,[54,55],"How does the atomic structure of metals make them good conductors?","Why do elements in the same group of the periodic table have similar properties?",[57,86,122,147,152],{"id":58,"data":59,"type":24,"maxContentLevel":35,"version":25,"reviews":62},"2417e295-0d9b-452f-98f7-088da342daa8",{"type":24,"markdownContent":60,"audioMediaId":61},"Chemical elements are the building blocks that make up everything you see, hear, smell and touch. They are **substances that cannot be broken down further using ordinary chemical reactions**. Each element is distinguished by its atomic structure, specifically the number of protons it has in its nucleus. These elements combine in various ways to form the diverse array of substances we encounter in our daily lives.\n\n![Graph](image://e7421107-84d8-4114-92d8-d87f64803a7f \"Sandbh, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.\")\n\nThe modern periodic table is a systematic way to organize these elements. It arranges them by **atomic number**, which is the number of protons in an element's nucleus. This arrangement results in groups of elements that share similar properties. This is because **the properties of an element are largely determined by the structure of its atoms**, particularly the arrangement of its electrons.\n\nCurrently, there are **118** known elements. Each of these elements has its own unique story, from its discovery to its uses in modern society. In this pathway, we will focus on the stories of nine specific elements, which, between them, demonstrate several of the key properties that elements can possess.","1f99d24e-9802-4fdf-893b-134b33851704",[63,75],{"id":64,"data":65,"type":66,"version":24,"maxContentLevel":35},"7e1df753-f810-4e50-88bc-0d52398a3896",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":67,"multiChoiceCorrect":69,"multiChoiceIncorrect":71,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},11,[68],"How many known elements are there currently?",[70],"118",[72,73,74],"124","158","137",{"id":76,"data":77,"type":66,"version":24,"maxContentLevel":35},"1c756dfa-983a-42fd-adac-fc086737b860",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":78,"multiChoiceCorrect":80,"multiChoiceIncorrect":82,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[79],"What is an atomic number?",[81],"The number of protons in an atom's nucleus",[83,84,85],"The number of neutrons in an atom's nucleus","The number of atoms in an a molecule","The number of electrons in a covalent bond",{"id":87,"data":88,"type":24,"maxContentLevel":35,"version":25,"reviews":91},"ab7d7425-d685-434a-8761-2131cb36f77c",{"type":24,"markdownContent":89,"audioMediaId":90},"The classification of elements has been a subject of scientific inquiry since the late 18th century. **Antoine Lavoisier**, a French chemist, made one of the earliest attempts to classify elements. In 1789, he divided them into metals and nonmetals, a basic distinction that is still recognized today.\n\n![Graph](image://f314db50-0507-4d47-8387-0be1e8cbc26a \"Dmitri Mendeleev, creator of the periodic table. Image: https://pixel17.com via Wikimedia.\")\n\nThe modern periodic table, however, owes its structure to **Dmitri Mendeleev**. In 1869, Mendeleev arranged the known elements by atomic weight, and he left gaps for elements that were yet to be discovered. This was a revolutionary idea at the time, and it allowed for the prediction of the properties of these undiscovered elements.\n\nMendeleev's periodic table has proven to be remarkably accurate. It has correctly predicted the existence and properties of several elements, including gallium, scandium, and germanium. Today, the periodic table is **organized by atomic number rather than atomic weight**, but the basic framework that Mendeleev established remains intact.","2ce1185f-0de7-4eb4-9b17-93d1ed0d92fb",[92,97,104,111],{"id":64,"data":93,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":94,"multiChoiceCorrect":95,"multiChoiceIncorrect":96,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[68],[70],[72,73,74],{"id":98,"data":99,"type":66,"version":24,"maxContentLevel":35},"fde05fcc-2ed0-41b3-9ff7-70777b1ca0b9",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":100,"clozeWords":102},[101],"The modern periodic table organizes elements by their atomic number, which is the number of protons in an element's nucleus.",[103],"protons",{"id":105,"data":106,"type":66,"version":24,"maxContentLevel":35},"1ef35d73-cb11-406f-b06c-00d81bb5d1b0",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":107,"clozeWords":109},[108],"In 1869, Dmitri Mendeleev arranged the known elements by atomic weight, predicting the properties of undiscovered elements.",[110],"atomic weight",{"id":112,"data":113,"type":66,"version":25,"maxContentLevel":35},"df25dc78-8c2b-4e28-907c-63530e7e96ec",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":114,"multiChoiceCorrect":116,"multiChoiceIncorrect":118,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[115],"Who created the framework for the modern periodic table?",[117],"Dmitri Mendeleev",[119,120,121],"Antoine Lavoisier","Marie Curie","Joseph Priestley",{"id":123,"data":124,"type":24,"maxContentLevel":35,"version":25,"reviews":127},"528e15b3-1d0b-4ca9-8dc8-b0ebdec7543e",{"type":24,"markdownContent":125,"audioMediaId":126},"Atoms are **the smallest units of an element**. They are the fundamental units of matter as we know it, and they are composed of even smaller particles: protons, neutrons, and electrons. Different combinations of these subatomic particles are what makes one element different to another.\n\n![Graph](image://627dea45-cc02-42c8-802d-3906636c4db6 \"The structure of an atom. Image: AG Caesar, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n**The atomic nucleus is the core of an atom**. It is positively charged and is surrounded by a cloud of negatively charged **electrons**. The nucleus contains **protons**, which contribute to the positive charge, and **neutrons**, which are neutral. The number of protons in the nucleus determines the atomic number of an element, which is the defining characteristic of each element.\n\nThe atomic nucleus was discovered by **Ernest Rutherford** through his gold foil experiment, shooting positively charged alpha particles at a piece of gold foil. He found that most of the atom's mass is concentrated in the nucleus, which is composed of protons and neutrons. The electrons, while essential for chemical reactions, **contribute very little to the atom's overall mass** due to their extremely small size.","f1951afb-c701-4aea-ba4e-d79e348d8ef6",[128],{"id":129,"data":130,"type":66,"version":24,"maxContentLevel":35},"6f99ea0d-a7c7-4274-a60b-442fc4588058",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":131,"multiChoiceQuestion":135,"multiChoiceCorrect":137,"multiChoiceIncorrect":139,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":142,"matchPairsPairs":144},[132,133,134],"10a94d54-2485-4710-b140-e6f59ff1b30f","85a11bac-2a49-4acf-baed-6572001bf863","96bc8de1-202c-4aae-8b9d-babf314b59d6",[136],"Who is the scientist credited with the discovery of the atomic nucleus?",[138],"Ernest Rutherford",[140,141,119],"Mendeleev","Henry Cavendish",[143],"Match the pairs below:",[145],{"left":138,"right":146,"direction":35},"Discovered the atomic nucleus",{"id":148,"data":149,"type":24,"maxContentLevel":35,"version":25},"0048169a-fb0d-45b0-a71a-835405094653",{"type":24,"markdownContent":150,"audioMediaId":151},"The **atomic mass** of an element **is the average mass of its atoms**. It is measured in atomic mass units (amu), also known as daltons (D). The atomic mass takes into account the mass of both the protons and neutrons in the nucleus, as these particles make up the majority of an atom's mass. **To calculate the atomic mass**, you simply **add the number of protons and neutrons** together.\n\nThe atomic mass is an important property of an element. It is used in calculations in chemistry, such as determining the amount of an element in a sample or predicting the outcome of a chemical reaction. The atomic mass is also used to calculate the molar mass of compounds, which is essential for **stoichiometry**. Stoichiometry is **the study of the amount of a substance required in chemical reactions** — both in terms of initial reactants and the resultant products.\n\n![Graph](image://770c5830-d537-4399-b2c0-d82265031899 \"A diagram showing the Stoichiometry of the Combustion of Methane. Notice, the amount of each type of element stays the same. Image: JyntoRobert A. RohdeJacek FHJynto, Public domain, via Wikimedia Commons\")","e6dc4cbb-4f6f-4659-aae6-38b80f02b470",{"id":153,"data":154,"type":24,"maxContentLevel":35,"version":25,"reviews":157},"a70e12f1-97f9-4dd2-bddf-d05dabeb881c",{"type":24,"markdownContent":155,"audioMediaId":156},"The atomic number, on the other hand, is the number of protons in an atom's nucleus. It is the defining characteristic of an element. For example, **an atom with six protons is always a carbon atom**. The atomic number is used to organize the elements in the periodic table.\n\n![Graph](image://e7421107-84d8-4114-92d8-d87f64803a7f \"Sandbh, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons.\")\n\nMendeleev’s original periodic table arranged elements by relative atomic mass. The modern periodic table, on the other hand, **arranges them by atomic number**, which is the number of protons in an atom's nucleus.\n\nThe periodic table is divided into horizontal rows called periods and vertical columns called groups. Elements in the same period have the same number of electron shells, while elements in the same group have the same number of electrons in their outermost shell, known as valence electrons. This arrangement results in **groups of elements that share similar properties**.\n\nThe arrangement of the periodic table reflects the periodic law proposed by Mendeleev. This law describes the fact that certain properties periodically reoccur across elements in the table. For example, the alkali metals in Group 1 such as lithium and potassium have quite major differences in their atomic numbers, but also share similar material properties.\n\nIn the case of Group 1 metals, this is that they are all highly reactive. They are also good conductors of heat and electricity: all because of their similar atomic structures.","c4874720-135b-4ce6-913c-edfe05a0062f",[158],{"id":159,"data":160,"type":66,"version":24,"maxContentLevel":35},"b562f932-3028-48a1-9b35-35ccecfe9a63",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":161,"multiChoiceCorrect":163,"multiChoiceIncorrect":165,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[162],"What are the horizontal rows in the periodic table called?",[164],"Periods",[166,167,168],"Groups","Families","Isotopes",{"id":170,"data":171,"type":25,"version":35,"maxContentLevel":35,"summaryPage":173,"introPage":181,"pages":187},"33b5e828-ca1b-4c9e-9051-2bc6a1b39d5c",{"type":25,"title":172},"Atomic Structure and Isotopes",{"id":174,"data":175,"type":35,"maxContentLevel":35,"version":24},"46a4e5f4-debf-46ec-a4d9-f5c9597f8a7c",{"type":35,"summary":176},[177,178,179,180],"Isotopes have the same number of protons but different numbers of neutrons","Carbon-12 and carbon-14 are isotopes used in carbon dating","Valence electrons determine an element's chemical properties","Metals are shiny, conduct heat, and are solid at room temperature (except mercury)",{"id":182,"data":183,"type":52,"maxContentLevel":35,"version":24},"ac62b1b7-fcfa-4e53-bd63-756c5ae2d51a",{"type":52,"intro":184},[185,186],"How does the number of valence electrons affect an element's reactivity?","Why do metals conduct electricity so well?",[188,272,311],{"id":189,"data":190,"type":24,"maxContentLevel":35,"version":25,"reviews":193},"b18e327c-c253-4430-a71d-e7a9de06d5c0",{"type":24,"markdownContent":191,"audioMediaId":192},"Isotopes are **different forms of the same element** that have **the same number of protons** but **different numbers of neutrons**. This means that while they have the same atomic number, they have different atomic masses. Even though isotopes of an element have different numbers of neutrons, they still exhibit the same chemical behavior because they have the same number of protons and electrons. This is why they are considered the same element.\n\nCarbon-12 and carbon-14 are examples of isotopes. Both have 6 protons, but carbon-12 has 6 neutrons while carbon-14 has 8. The ratio of these isotopes in a sample can be used in carbon dating, a method used to determine the age of organic remains up to 60,000 years old.","5c70a364-9e7b-4c55-82aa-1f4d4bde6292",[194,213,224,243,254],{"id":195,"data":196,"type":66,"version":24,"maxContentLevel":35},"9fa1214d-ed1a-400b-9bb0-571a6acebeab",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":197,"multiChoiceQuestion":201,"multiChoiceCorrect":203,"multiChoiceIncorrect":205,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":209,"matchPairsPairs":210},[198,199,200],"eb07d82a-5f99-4c7b-aa35-a300e5dc0c3c","93f857a8-8398-4631-8c32-62bd7628ee66","eb0c2d87-0f07-43da-8d7c-4e9c9bb2136e",[202],"What is the number of protons in Carbon-12 and Carbon-14?",[204],"6",[206,207,208],"8","100","26",[143],[211],{"left":212,"right":204,"direction":35},"Number of protons in Carbon-12 and Carbon-14",{"id":198,"data":214,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":215,"multiChoiceQuestion":216,"multiChoiceCorrect":218,"multiChoiceIncorrect":219,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":220,"matchPairsPairs":221},[195,199,200],[217],"What is the number of neutrons in Carbon-14?",[206],[204,207,208],[143],[222],{"left":223,"right":206,"direction":35},"Number of neutrons in Carbon-14",{"id":225,"data":226,"type":66,"version":24,"maxContentLevel":35},"a270f625-b542-4145-beb0-27022ea0d1f9",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":227,"multiChoiceQuestion":231,"multiChoiceCorrect":233,"multiChoiceIncorrect":235,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":239,"matchPairsPairs":240},[228,229,230],"ecd25d07-df52-44b3-8ed4-d8953bedda39","dae9a85f-9f7d-4128-b731-c5e558d4adb5","9130e33f-4c3b-49f0-8123-be3cd5e0104b",[232],"Which of the following best describes the atomic number?",[234],"Number of protons in an atom",[236,237,238],"Number of protons and neutrons in an atom","Distance from the center of an atom","The arrangement of protons, neutrons, and electrons in an atom",[143],[241],{"left":242,"right":234,"direction":35},"Atomic number",{"id":228,"data":244,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":245,"multiChoiceQuestion":246,"multiChoiceCorrect":248,"multiChoiceIncorrect":249,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":250,"matchPairsPairs":251},[225,229,230],[247],"Which of the following best describes atomic mass?",[236],[234,237,238],[143],[252],{"left":253,"right":236,"direction":35},"Atomic mass",{"id":255,"data":256,"type":66,"version":24,"maxContentLevel":35},"35de950d-5779-4d13-93f0-ef1db20d1810",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":257,"multiChoiceQuestion":261,"multiChoiceCorrect":263,"multiChoiceIncorrect":264,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":268,"matchPairsPairs":269},[258,259,260],"cbeeb34c-3805-4890-a534-ee1fa496e032","49b835ef-34ae-4bb6-9d06-3ce5c72351c1","768da50d-934e-4bfe-9e76-500b3f0751db",[262],"Which term refers to atoms that have the same number of protons but different numbers of neutrons?",[168],[265,266,267],"Electrons","Sodium and Chlorine atoms","Metals",[143],[270],{"left":168,"right":271,"direction":35},"Have the same number of protons but different number of neutrons",{"id":273,"data":274,"type":24,"maxContentLevel":35,"version":35,"reviews":277},"eb188336-e5c5-4a91-8110-fe7ccc8e39ce",{"type":24,"markdownContent":275,"audioMediaId":276},"The chemical properties of an element are **determined by the arrangement of its electrons**, particularly the electrons in its outermost shell, known as **valence electrons**. These properties include chemical reactivity, flammability, and reactivity with acids. Electrons are arranged in shells around the nucleus. The further a shell is from the nucleus, the larger it is and the more electrons it can hold.\n\nThe electrons in the outermost shell have **the highest energy** and are **the most involved in chemical reactions**. The number and arrangement of valence electrons determine an element's chemical properties. These electrons are involved in forming chemical bonds with other atoms. For example, sodium and chlorine atoms bond to form table salt, with sodium donating an electron to chlorine to become sodium chloride.","bc77befd-e974-4b58-aceb-0f277716f039",[278,289,300],{"id":258,"data":279,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":280,"multiChoiceQuestion":281,"multiChoiceCorrect":283,"multiChoiceIncorrect":284,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":285,"matchPairsPairs":286},[255,259,260],[282],"What is arranged in shells around the nucleus?",[265],[168,266,267],[143],[287],{"left":265,"right":288,"direction":35},"Arranged in shells around the nucleus",{"id":259,"data":290,"type":66,"version":25,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":291,"multiChoiceQuestion":292,"multiChoiceCorrect":294,"multiChoiceIncorrect":295,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":296,"matchPairsPairs":297},[255,258,260],[293],"Which two atoms bond together to form table salt?",[266],[168,265,267],[143],[298],{"left":266,"right":299,"direction":35},"Bond to form table salt",{"id":301,"data":302,"type":66,"version":24,"maxContentLevel":35},"5eac5e61-566a-4acf-9d73-2294960d4fce",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":303,"multiChoiceCorrect":305,"multiChoiceIncorrect":307,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[304],"What term is used to describe the electrons in an element's outermost shell, which determine its chemical properties?",[306],"Valence electrons",[308,309,310],"Positive electrons","Ionized electrons","Free electrons",{"id":312,"data":313,"type":24,"maxContentLevel":35,"version":25,"reviews":316},"2063e3f2-49c8-4fb5-a7c9-0ca56e468d02",{"type":24,"markdownContent":314,"audioMediaId":315},"The physical properties of an element, such as color, density, melting point, and boiling point, are key to its identification and classification. These properties can be observed or measured without changing the composition of the material. Physical properties are determined by the structure of an element's atoms and the way they interact with each other. For example, the density of an element is determined by the mass of its atoms and the space they occupy.\n\n![Graph](image://bba3e1b8-060d-45ab-83a3-14b6225bf779 \"The various cool properties of different elements. Image: Bionerd, Ivar Leidus, Alchemist-hp and Jurii via Wikimedia\")\n\nMetals, which make up about 80% of the elements on the periodic table, have distinctive physical properties. They tend to have a shiny luster, conduct heat and electricity, have high tensile strength, and are solid at room temperature, with the exception of mercury. These properties are a result of the structure of metal atoms and the way their electrons are arranged.","a136e15a-fc5b-4f40-875f-8572cb817e36",[317],{"id":260,"data":318,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":319,"multiChoiceQuestion":320,"multiChoiceCorrect":322,"multiChoiceIncorrect":323,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":324,"matchPairsPairs":325},[255,258,259],[321],"What makes up about 80% of the elements on the periodic table?",[267],[168,265,266],[143],[326],{"left":267,"right":327,"direction":35},"Make up about 80% of the elements on the periodic table",{"id":329,"data":330,"type":25,"version":25,"maxContentLevel":35,"summaryPage":332,"introPage":340,"pages":346},"51b1f4f4-dcee-4fee-b370-88ae039b6c7c",{"type":25,"title":331},"Periodic Trends and Properties",{"id":333,"data":334,"type":35,"maxContentLevel":35,"version":24},"46549ca6-dee8-4c05-a8f3-ea4fe4603f73",{"type":35,"summary":335},[336,337,338,339],"Periodic trends predict how elements behave chemically","Electronegativity is an atom's pull on electrons in a bond","Atomic radius shrinks across a period, grows down a group","Ionization energy is the energy to yank an electron from an atom",{"id":341,"data":342,"type":52,"maxContentLevel":35,"version":24},"e11f1a25-ebf0-4fb0-96a7-bc852a1888ef",{"type":52,"intro":343},[344,345],"What makes hydrogen the lightest element?","What are the three naturally occurring isotopes of hydrogen?",[347,375],{"id":348,"data":349,"type":24,"maxContentLevel":35,"version":25,"reviews":352},"6ce7ab8b-753c-4934-a98e-4bdf0722265f",{"type":24,"markdownContent":350,"audioMediaId":351},"Periodic trends are **patterns in the properties of elements** that occur **across periods and groups on the periodic table**. These trends help predict the chemical behavior of elements and are a result of the periodic law proposed by Mendeleev.\n\n![Graph](image://f1953607-0a23-4175-b493-b278accc2d09 \"An illustration of periodic trends on the periodic table. Sandbh, vector + translation by Habitator terrae, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nMajor periodic trends include electronegativity, ionization energy, atomic radius, and electron affinity. **Electronegativity** is a measure of an atom's ability to attract electrons in a chemical bond. **Ionization** energy is the energy required to remove an electron from an atom. **Atomic radius** is the size of an atom. Electron affinity is the energy change that occurs when an electron is added to a neutral atom.","bad6e0cd-fade-4ac0-9129-e2b583b0a38f",[353,364],{"id":229,"data":354,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":355,"multiChoiceQuestion":356,"multiChoiceCorrect":358,"multiChoiceIncorrect":359,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":360,"matchPairsPairs":361},[225,228,230],[357],"Which of the following best describes the atomic radius?",[237],[234,236,238],[143],[362],{"left":363,"right":237,"direction":35},"Atomic Radius",{"id":132,"data":365,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":366,"multiChoiceQuestion":367,"multiChoiceCorrect":369,"multiChoiceIncorrect":370,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":371,"matchPairsPairs":372},[129,133,134],[368],"Who is the scientist that proposed the periodic law?",[140],[138,141,119],[143],[373],{"left":140,"right":374,"direction":35},"Proposed the periodic law",{"id":376,"data":377,"type":24,"maxContentLevel":35,"version":25,"reviews":380},"2accf7dd-5b38-49fa-b9b1-3dcd9478bf16",{"type":24,"markdownContent":378,"audioMediaId":379},"These trends can be explained by the structure of atoms. For example, atomic radius **decreases as you move from left to right** across a period. This is because the number of protons in the nucleus increases, pulling the electrons in closer and reducing the size of the atom.\n\nOn the other hand, atomic radius **increases as you move down a group** because additional electron shells are added, increasing the size of the atom.","488d37f2-e79b-4a23-b799-a1edaac3afea",[381],{"id":382,"data":383,"type":66,"version":24,"maxContentLevel":35},"8f7eaeca-946d-422a-980b-6e45cd69ac02",{"type":66,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":384,"binaryCorrect":386,"binaryIncorrect":388},[385],"What happens to atomic radius as you move from left to right in a period?",[387],"It decreases",[389],"It increases",{"id":391,"data":392,"type":27,"maxContentLevel":35,"version":35,"orbs":395},"b72e80b4-0627-49a7-8854-5c7db6a0de15",{"type":27,"title":393,"tagline":394},"Hydrogen","The most abundant element in the universe.",[396,483,573],{"id":397,"data":398,"type":25,"version":35,"maxContentLevel":35,"summaryPage":400,"introPage":408,"pages":414},"864ff4db-d624-44a8-b011-92507e6372e6",{"type":25,"title":399},"Introduction to Hydrogen",{"id":401,"data":402,"type":35,"maxContentLevel":35,"version":24},"29095871-70fd-46ab-a60e-da1c2bfaad3d",{"type":35,"summary":403},[404,405,406,407],"Hydrogen is the lightest and most abundant element in the universe","Henry Cavendish discovered hydrogen in 1766 during an experiment with zinc and hydrochloric acid","Hydrogen atoms usually have one proton and one electron, making them the simplest atoms","Hydrogen has three isotopes: protium, deuterium, and tritium",{"id":409,"data":410,"type":52,"maxContentLevel":35,"version":24},"ff7e67dd-ea66-4e03-8db3-7c8997ea2c95",{"type":52,"intro":411},[412,413],"Why is pure hydrogen so rare on Earth?","How does hydrogen contribute to the formation of water?",[415,432,449,466],{"id":416,"data":417,"type":24,"maxContentLevel":35,"version":25,"reviews":420},"8a7b9a3f-bb7d-4bba-a323-a652993e6d14",{"type":24,"markdownContent":418,"audioMediaId":419},"![Graph](image://6f4afc74-49a0-4b95-b63a-4ba68ec9fcb6 \"Hydrogen atom. Image: BruceBlaus, CC BY 3.0 \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")\n\nHydrogen, denoted as **the first element in the periodic table** with an atomic number of one, holds the distinction of being the lightest and most abundant chemical substance in the universe. If you were to learn about just one element, hydrogen would probably be the obvious candidate – it makes up **90% of all atoms** in the known universe.\n\nThis is no coincidence. Hydrogen is the most abundant element in the universe because **it is the simplest**. It has the atomic number one, meaning its nucleus contains just a single proton.\n\nThe significance of hydrogen extends beyond its abundance. Hydrogen molecules, which are composed of two hydrogen atoms, play a crucial role in the formation of stars and galaxies. These molecules provide the raw material for the creation of stars and galaxies. **Without hydrogen, the universe as we know it would not exist**.","9fb7e084-a5b2-4e7b-bba1-42ab8fc6acdc",[421],{"id":422,"data":423,"type":66,"version":24,"maxContentLevel":35},"0a7d273a-44ad-4317-ad17-22b2075b55e3",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":424,"multiChoiceCorrect":426,"multiChoiceIncorrect":428,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[425],"What is the position of Hydrogen in the periodic table?",[427],"First",[429,430,431],"Second","Third","Fourth",{"id":433,"data":434,"type":24,"maxContentLevel":35,"version":25,"reviews":437},"122773f9-aad4-45cd-afb6-8c0945859ef7",{"type":24,"markdownContent":435,"audioMediaId":436},"Despite its abundance in the universe, **pure hydrogen is rarely found on Earth**. This is due to its light weight and high reactivity, which cause it to quickly combine with other elements. As a result, hydrogen is usually found on our planet in combination with other elements, such as in water molecules, rather than in its pure form.\n\nThe discovery of hydrogen as a distinct substance is credited to the British scientist **Henry Cavendish** in 1766. Cavendish made this discovery during an experiment with zinc and hydrochloric acid. His work marked a significant milestone in the field of chemistry, as it led to the identification of a new, distinct element.\n\n![Graph](image://657898e3-c697-44e6-81ba-20a810945819 \"Henry Cavendish. Image: Public domain, Wellcome Images via Wikimedia.\")","99fc88ae-f29e-4afa-b02c-48e57e501b55",[438],{"id":133,"data":439,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":440,"multiChoiceQuestion":441,"multiChoiceCorrect":443,"multiChoiceIncorrect":444,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":445,"matchPairsPairs":446},[129,132,134],[442],"Who is credited with the discovery of hydrogen?",[141],[138,140,119],[143],[447],{"left":141,"right":448,"direction":35},"Discovered hydrogen",{"id":450,"data":451,"type":24,"maxContentLevel":35,"version":25,"reviews":454},"acaa86fa-c17c-4933-8b40-4d92c430f7c9",{"type":24,"markdownContent":452,"audioMediaId":453},"Cavendish's experiments with hydrogen did not stop at its discovery. He also found that when hydrogen is burned, it produces water. This finding paved the way for his later discovery that water is composed of hydrogen and oxygen, a fundamental principle in the field of chemistry.\n\nDespite its discovery in 1766, hydrogen was not named until 1783. The name, which means 'water-former', was given by Antoine Lavoisier. This name reflects the element's ability to form water when burned.\n\nHydrogen is the simplest element, with most hydrogen atoms consisting of one proton and one electron. This means it has an atomic number of one – atomic number being the number of protons in an atom’s nucleus. Despite its simplicity, hydrogen plays a crucial role in many chemical reactions and processes.","352fbd02-99af-4e69-a179-a98e0ae85cfc",[455],{"id":134,"data":456,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":457,"multiChoiceQuestion":458,"multiChoiceCorrect":460,"multiChoiceIncorrect":461,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":462,"matchPairsPairs":463},[129,132,133],[459],"Who is the scientist responsible for naming hydrogen?",[119],[138,140,141],[143],[464],{"left":119,"right":465,"direction":35},"Named hydrogen",{"id":467,"data":468,"type":24,"maxContentLevel":35,"version":35,"reviews":471},"6b00342a-694d-428d-a9e1-5642e4570353",{"type":24,"markdownContent":469,"audioMediaId":470},"The structure of hydrogen is unique in that it is the only atom that typically does not contain neutrons. This is due to the fact that the single proton and electron in hydrogen are sufficient to form a stable atom. This lack of neutrons further contributes to hydrogen's lightness and simplicity.\n\n![Graph](image://0d0c9dd6-8ac9-4414-9e58-a7cfc2db354e \"Isotopes of Hydrogen. Image: Dirk Hünniger via Wikimedia.\")\n\nHydrogen has three naturally occurring isotopes: protium, deuterium, and tritium. Protium, the most common isotope, consists of one proton and one electron. This accounts for more than 99.98% of the hydrogen in the universe. Deuterium, a stable isotope, contains one proton, one neutron, and one electron. Tritium, the rarest and most radioactive isotope, has one proton, two neutrons, and one electron.","be06732f-f79a-492f-9d43-17d411aadb29",[472],{"id":473,"data":474,"type":66,"version":25,"maxContentLevel":35},"be57ac95-0b69-4954-b227-dbf4f33813a2",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":475,"multiChoiceCorrect":477,"multiChoiceIncorrect":479,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[476],"Which of these is NOT a naturally occuring isotope of Hydrogen?",[478],"Actinidium",[480,481,482],"Protium","Deuterium","Tritium",{"id":484,"data":485,"type":25,"version":35,"maxContentLevel":35,"summaryPage":487,"introPage":495,"pages":501},"3280e9ff-7b7a-4a53-9387-06d35d060de8",{"type":25,"title":486},"Hydrogen in the Universe",{"id":488,"data":489,"type":35,"maxContentLevel":35,"version":24},"95192fa1-2649-4698-aeb0-a258401b47d7",{"type":35,"summary":490},[491,492,493,494],"Hydrogen makes up 75% of normal matter by mass in the universe","Stars, including our sun, are mostly made of hydrogen plasma","Stellar nucleosynthesis in stars creates heavier elements like carbon and oxygen","Hydrogen is most commonly found on Earth in water molecules (H2O)",{"id":496,"data":497,"type":52,"maxContentLevel":35,"version":24},"9e5f55d9-d10a-4532-8192-62412d7d792f",{"type":52,"intro":498},[499,500],"Why is hydrogen classified in the s-block of the periodic table?","What makes hydrogen's atomic structure unique compared to other elements?",[502,515,532,548,568],{"id":503,"data":504,"type":24,"maxContentLevel":35,"version":25,"reviews":507},"5600725b-5c32-40b0-a1e5-47e6ac4169c2",{"type":24,"markdownContent":505,"audioMediaId":506},"Hydrogen is the primary substance that makes up the **vast majority of the matter** in our universe, forming stars through the process of nuclear fusion. It makes up **75% of normal matter by mass**, and **90% of normal matter by number of atoms**. The hydrogen found throughout the universe is often in atomic and plasma states.\n\nAtomic hydrogen consists of single atoms. In hydrogen plasma, hydrogen’s electrons and protons are no longer bound together. As a result, hydrogen plasma is very good at **conducting electricity** and **emitting energy**. Stars, including our sun, are largely made of hydrogen in the plasma state.\n\n![Graph](image://c8658d91-f8de-4326-bab8-28ffe7cdfdca \"Plasma state hydrogen in a laboratory. Image: Al126, CC BY-SA 4.0, https://creativecommons.org/licenses/by-sa/4.0/, via Wikimedia\")","d53567f0-f791-4076-8649-3febfee4d1aa",[508],{"id":509,"data":510,"type":66,"version":24,"maxContentLevel":35},"3b4c90d2-8ff6-45d4-90c8-c9d4de34f23d",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":511,"clozeWords":513},[512],"Stars, including our sun, are largely made of hydrogen in the plasma state.",[514],"plasma",{"id":516,"data":517,"type":24,"maxContentLevel":35,"version":25,"reviews":520},"02cbe648-09a4-4591-8d31-f32c435dd2ce",{"type":24,"markdownContent":518,"audioMediaId":519},"The process of nuclear fusion in stars involves the **combination of hydrogen atoms to form helium**. This process releases energy in the form of light and heat – the sources of most other energy in the universe, and almost all of the energy on our own planet.\n\nOur sun, like other stars, fuses hydrogen atoms to produce helium. **Helium is the second element in the periodic table**, with **two protons** in its nucleus. It is estimated that the sun fuses about 600 million tons of hydrogen every second, yielding 596 million tons of helium. The energy released during this process is what makes life on Earth possible.","f7caf9b2-847d-480e-8884-e61c49648980",[521],{"id":522,"data":523,"type":66,"version":24,"maxContentLevel":35},"503df365-8a05-4e7a-98eb-4080de908757",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":524,"multiChoiceCorrect":526,"multiChoiceIncorrect":528,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[525],"What is the process in stars that involves the combination of hydrogen atoms to form helium, releasing energy in the form of light and heat?",[527],"Nuclear fusion",[529,530,531],"Nuclear fission","Nucleosynthesis","Nucleosis",{"id":533,"data":534,"type":24,"maxContentLevel":35,"version":25,"reviews":537},"de0136a1-d27f-494d-b424-4dde9b9a5396",{"type":24,"markdownContent":535,"audioMediaId":536},"Hydrogen, the lightest and most abundant element in the universe, serves as the precursor to other elements. **Without hydrogen, the formation of other elements would not be possible**. As previously mentioned, stars convert hydrogen into helium and subsequently into heavier elements through a process known as nuclear fusion.\n\nWhen specifically applied to the creation of new elements in stars, this is described as **stellar nucleosynthesis**. Stellar nucleosynthesis is responsible for the creation of the vast majority of heavier elements. These heavy elements are created in different types of stars as they die or explode.","0ffcbd20-7706-4472-94eb-fabb544ed21b",[538],{"id":539,"data":540,"type":66,"version":24,"maxContentLevel":35},"c5d21952-735d-49ad-8c5c-645ce664e2f8",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":541,"multiChoiceCorrect":543,"multiChoiceIncorrect":544,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[542],"What is the lightest and most abundant element in the universe?",[393],[545,546,547],"Helium","Lithium","Oxygen",{"id":549,"data":550,"type":24,"maxContentLevel":35,"version":25,"reviews":553},"4354a3f6-d879-4466-ac83-708df61cb2f0",{"type":24,"markdownContent":551,"audioMediaId":552},"**Stellar nucleosynthesis** has occurred since the original creation of the universe during the Big Bang. The elements created during the big bang were hydrogen, lithium, and helium. Subsequent stellar nucleosynthesis is responsible for the creation of elements such as **carbon**, **oxygen**, and **iron** (we'll learn more about these!) which are essential for life on Earth.\n\nWithout stellar nucleosynthesis, these elements, and consequently life as we know it, would not exist. On Earth, hydrogen is most commonly found in water molecules, which consist of two hydrogen atoms and one oxygen atom. **This makes water the most common source of hydrogen on our planet**. Given that about 71% of the Earth's surface is covered by water, **the abundance of hydrogen on Earth is evident**.\n\n![Graph](image://e668e2b1-3bb1-43da-82b5-a63f45601e87 \"Hydrogen in its most common form on Earth - H20. Image: Jjm596 via Wikimedia\")","3ae374ec-a585-40f4-b915-b1e2f89b9ebe",[554,561],{"id":555,"data":556,"type":66,"version":24,"maxContentLevel":35},"cbe50f8a-fade-41ea-aed3-e5d87ee70c5c",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":557,"activeRecallAnswers":559},[558],"What is responsible for the creation of elements such as carbon, oxygen, and iron?",[560],"Stellar nucleosynthesis",{"id":562,"data":563,"type":66,"version":24,"maxContentLevel":35},"6a89adfc-7fd6-43e3-b82a-485adfa04788",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":564,"clozeWords":566},[565],"Hydrogen is most commonly found in water molecules on Earth.",[567],"water",{"id":569,"data":570,"type":24,"maxContentLevel":35,"version":35},"0e92ddac-5a6a-42e2-b5b2-262d9023118c",{"type":24,"markdownContent":571,"audioMediaId":572},"Hydrogen also forms part of many **organic compounds**, including hydrocarbons such as **methane** and **carbohydrates**. These compounds, which are essential for life on Earth, highlight the importance of hydrogen in the field of organic chemistry, which is the study of carbon-containing substances. \n\nDespite being the most abundant element in the universe, **pure hydrogen is relatively rare on Earth**. This is due to its high reactivity and lightness. Not only does it combine quickly with other elements, pure hydrogen is light enough to escape Earth’s gravitational pull with ease. As a result, hydrogen is usually found in combination with other elements.","f173ac54-4adf-4470-a509-44beadbfea52",{"id":574,"data":575,"type":25,"version":24,"maxContentLevel":35,"summaryPage":577,"introPage":585,"pages":591},"4939b26f-9852-4b8a-b809-d14c75c3e009",{"type":25,"title":576},"Hydrogen in Energy and Chemistry",{"id":578,"data":579,"type":35,"maxContentLevel":35,"version":24},"4d512ae5-dee6-42cf-b567-eba135daa48e",{"type":35,"summary":580},[581,582,583,584],"Fossil fuels are made from carbon and hydrogen, powering the industrial revolution","Hydrogen fuel cells generate electricity and water, making them a clean energy source","Hydrogen's simple structure (one proton, one electron) sets it apart from other s-block elements","Hydrogen exists as diatomic molecules, unlike alkali metals, sparking classification debates",{"id":586,"data":587,"type":52,"maxContentLevel":35,"version":24},"145212dc-6ee1-4356-b6f1-57d45116cdcb",{"type":52,"intro":588},[589,590],"How does radium's unstable atomic structure lead to high radioactivity?","What particles and energy does Ra-226 emit to stabilize?",[592,629,653],{"id":593,"data":594,"type":24,"maxContentLevel":35,"version":24,"reviews":597},"c9692b88-ced1-4bee-ae2d-edf9f93fc42c",{"type":24,"markdownContent":595,"audioMediaId":596},"Hydrogen plays a crucial role in the field of energy production. Fossil fuels such as coal, oil, and natural gases, which powered the industrial revolution and changed human societies, are made from carbon and hydrogen. Such hydrocarbon fuels are of great importance to the energy industry and society more widely.\n\nHydrogen fuel cells can be used to generate energy. In a fuel cell, hydrogen and oxygen combine to produce electricity and water. This makes hydrogen a clean and renewable source of energy. Hydrogen fuel cells have various potential applications, including transportation and portable power systems.\n\n![Graph](image://bacd8c21-8d58-458b-aa27-b9af9a0c269b \"Hydrogen fuel cell powering a vehicle. Image: Dr. Artur Braun (Arturbraun) via Wikimedia.\")\n","eee4e9d9-ec89-4cf8-9049-9e52004bc9de",[598,616],{"id":599,"data":600,"type":66,"version":24,"maxContentLevel":35},"649fe517-8c3f-4aaf-97ea-824c4725f6d2",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":601,"multiChoiceQuestion":605,"multiChoiceCorrect":607,"multiChoiceIncorrect":609,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":613,"matchPairsPairs":614},[602,603,604],"7e621897-11e6-4018-aa47-f5ad9d77a7be","559330e7-d140-4a0e-b8f6-c86d5834fe43","3e63580c-f0ff-4ddb-9177-674b038c6c35",[606],"Which of the following most closely applies to hydrogen?",[608],"Clean and renewable source of energy",[610,611,612],"Powered the industrial revolution","Formed from decay of thorium","Radioactive, present in the earth's crust",[143],[615],{"left":393,"right":608,"direction":35},{"id":602,"data":617,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":618,"multiChoiceQuestion":619,"multiChoiceCorrect":621,"multiChoiceIncorrect":623,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":626,"matchPairsPairs":627},[599,603,604],[620],"What powered the Industrial Revolution?",[622],"Fossil Fuels",[393,624,625],"Radium","Uranium",[143],[628],{"left":622,"right":610,"direction":35},{"id":630,"data":631,"type":24,"maxContentLevel":35,"version":24,"reviews":634},"fc1ef517-80d4-4708-8daf-ad5653f84f32",{"type":24,"markdownContent":632,"audioMediaId":633},"\nResearch into hydrogen fusion reveals exciting possibilities for energy production. While it has not yet been possible to produce energy in large quantities using hydrogen fusion, recent scientific advances have made this prospect more likely.\n\nHydrogen is part of the s-block of the periodic table, which includes elements with their outermost electron in an s orbital. This orbital is a spherically shaped region that orbits around the nucleus of the atom.\n\nDespite its placement in the periodic table, hydrogen differs significantly from other s-block elements. These include the highly reactive alkali metals such as lithium, sodium, and calcium. The difference in properties is a result of hydrogen’s simple atomic structure, consisting as it does of a single proton and electron.\n","7650ca70-b302-4c3d-b398-bf55824d42b2",[635,646],{"id":230,"data":636,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":637,"multiChoiceQuestion":638,"multiChoiceCorrect":640,"multiChoiceIncorrect":641,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":642,"matchPairsPairs":643},[225,228,229],[639],"Which of the following best describes atomic structure?",[238],[234,236,237],[143],[644],{"left":645,"right":238,"direction":35},"Atomic Structure",{"id":647,"data":648,"type":66,"version":24,"maxContentLevel":35},"86541298-f300-40cf-9dec-5fb6f0971c76",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":649,"activeRecallAnswers":651},[650],"What are hydrogen fuel cells used for?",[652],"Generating energy",{"id":654,"data":655,"type":24,"maxContentLevel":35,"version":24,"reviews":658},"1a1b1a59-06b2-4abf-98cf-06198d646ece",{"type":24,"markdownContent":656,"audioMediaId":657},"\nThis unique structure gives hydrogen distinct properties, setting it apart from other elements in the s-block.\n\n![Graph](image://90b9a203-2216-41dc-b63b-e8006503b420 \"Different kinds or atomic orbitals. Image: haade via Wikimedia\")\n\nThe unique position of hydrogen in the periodic table has led to debates among scientists about its proper classification. While it shares a group with the alkali metals, it differs from them in important ways. For example, hydrogen exists as diatomic molecules, while alkali metals do not. This has led to ongoing discussions about the best way to classify hydrogen within the periodic table.\n","d5bba794-de8b-43bf-9f98-636f37e9c235",[659],{"id":660,"data":661,"type":66,"version":24,"maxContentLevel":35},"256fb07e-7f7a-4a1d-8589-df3a2c4af184",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":662,"activeRecallAnswers":664},[663],"What is a unique characteristic of hydrogen compared to alkali metals?",[665],"Exists as diatomic molecules",{"id":667,"data":668,"type":27,"maxContentLevel":35,"version":25,"orbs":670},"d6df0fa1-5a39-432b-8863-e0fc26d5c3c3",{"type":27,"title":624,"tagline":669},"One of the most important radioactive elements.",[671,755,841],{"id":672,"data":673,"type":25,"version":25,"maxContentLevel":35,"summaryPage":675,"introPage":683,"pages":689},"ae3fa352-322d-4281-8e41-786e0d09d9e2",{"type":25,"title":674},"The Discovery and Properties of Radium",{"id":676,"data":677,"type":35,"maxContentLevel":35,"version":24},"9852d795-1e59-4835-b996-09336fdf2efe",{"type":35,"summary":678},[679,680,681,682],"Radium was discovered by Marie and Pierre Curie in 1898","Radium glows in the dark due to its radioactivity","Radium is formed by the decay of uranium and thorium","Radium has 88 protons and 33 known isotopes",{"id":684,"data":685,"type":52,"maxContentLevel":35,"version":24},"e7d0ee4e-425f-434d-9441-856cef80e81f",{"type":52,"intro":686},[687,688],"What made radium glow in the dark?","Why did the use of radium decline over time?",[690,695,726,731],{"id":691,"data":692,"type":24,"maxContentLevel":35,"version":25},"493ca971-46ff-4c63-8251-b0480b51bd73",{"type":24,"markdownContent":693,"audioMediaId":694},"**Radium**, a radioactive element, was first discovered by the esteemed scientists **Marie** and **Pierre Curie**. Between them, Marie and Pierre Curie shook the scientific world. Their work on radium and radioactivity paved the way for further research on radioactive elements and their potential applications, with significant consequences for the wider world.\n\nRadium is formed through the radioactive decay of **uranium** and **thorium**. It can be found in uranium ores and thorium ores. **Less than 100 grams** of radium is produced annually.\n\n![Graph](image://24b70622-c9e3-4699-a884-e8fc9219f27b \"A small piece of radium. grenadier, CC BY 3.0 \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")\n\nRadium has had various applications throughout history. One of the most notable uses of radium was in **luminous paints** for watches, aircraft switches, and instrument dials. The radioactivity of radium causes it to glow, making it seemingly ideal for use in these applications where visibility in low light conditions is crucial.","ee41b76c-7f32-40cf-a201-4203acd354fc",{"id":696,"data":697,"type":24,"maxContentLevel":35,"version":25,"reviews":700},"92a9702d-c81b-4109-a685-0fd7f72d1a38",{"type":24,"markdownContent":698,"audioMediaId":699},"The discovery of radium was made by Marie Curie and Pierre Curie in 1898. In the same year, they discovered another new radioactive element - **polonium**. Marie Curie coined the term ‘**radioactive**’ to describe these elements that emitted energy through atomic decay.\n\n![Graph](image://2cd48784-435a-47c0-8398-9f50f1f15144 \"Marie Curie. Image: Public domain via Wikimedia\")\n\nThe Curies' discovery of radium was a result of their extensive research on a mineral called **pitchblende**, which is primarily composed of uranium. They managed to extract 1mg of radium from ten tonnes of pitchblende, demonstrating the rarity and difficulty of extracting radium in significant quantities.\n\nMarie Curie's work on radium earned her two Nobel prizes, making her the **first woman to receive a Nobel prize** and the first person to receive a second Nobel prize. She was awarded her first Nobel prize in Physics in 1903, shared with Pierre Curie and Henri Becquerel, for their research on radiation. She received her second Nobel prize in Chemistry in 1911.\n\nTragically, Marie Curie’s foundational work in the study of radioactivity was also the cause of her death. She spent many years working with radioactive substances such as radium, before the extremely dangerous effects of such substances were widely understood. This was almost certainly a factor in her eventual death from aplastic anemia.","48f02ed8-9278-4c5b-9110-eb4a3e6f2f64",[701,708,719],{"id":702,"data":703,"type":66,"version":24,"maxContentLevel":35},"3acb3229-f9ca-4ade-b309-98bb092a5660",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":704,"clozeWords":706},[705],"Radium, discovered by Marie and Pierre Curie, is formed through the radioactive decay of uranium and thorium.",[707],"uranium",{"id":709,"data":710,"type":66,"version":24,"maxContentLevel":35},"f05b07bc-a304-4bcd-bdea-87c77a31b080",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":711,"multiChoiceCorrect":713,"multiChoiceIncorrect":715,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[712],"What mineral did the Curies research to discover radium?",[714],"Pitchblende",[716,717,718],"Curium","Arsenic","Onyx",{"id":720,"data":721,"type":66,"version":24,"maxContentLevel":35},"24ba9df7-c820-44fe-bcf1-7252c85e2b1d",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":722,"activeRecallAnswers":724},[723],"How is radium formed?",[725],"Radioactive decay of uranium and thorium",{"id":727,"data":728,"type":24,"maxContentLevel":35,"version":25},"728aa114-57de-4865-933f-4a9857b6f235",{"type":24,"markdownContent":729,"audioMediaId":730},"Radium is formed by the radioactive decay of **uranium** and **thorium**. This process involves radioactive atoms giving off radiation in the form of energy or particles to reach a stable state. This decay process is a **fundamental aspect of radioactivity** and is responsible for the creation of many radioactive elements, including radium.\n\n![Graph](image://9e6f472a-583e-447c-9771-f5de78bd9ca4 \"The decay chain of uranium. User:Tosaka, CC BY 3.0 \u003Chttps://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons\")\n\n**Pure radium is silvery white**. When it’s exposed to air, it reacts quickly with nitrogen. This reaction produces **radium nitride** which creates a black surface layer.\n\nRadium has **88** protons in its atomic nucleus, which gives it the **atomic number 88**. It has 33 known isotopes. The most common of these are Ra-226 and Ra-228, which are produced by the radioactive decay of uranium and thorium respectively.\n\nThese isotopes are distinguished by the number of neutrons in their atomic nucleus. Despite having different numbers of neutrons, **all isotopes of an element share the same number of protons** and thus have the same atomic number.","7a18142d-68e1-4b61-bfc4-0e9eda20180b",{"id":732,"data":733,"type":24,"maxContentLevel":35,"version":25,"reviews":736},"a813a661-0031-4eb4-81f6-dd97a052182c",{"type":24,"markdownContent":734,"audioMediaId":735},"Radium is known for its **high radioactivity**. This radioactivity is what makes radium **both useful and hazardous**.\n\nBut what does radioactivity actually mean? In simple terms, it is where **an element’s atoms are unstable**, and therefore emit particles and energy from their nucleus.\n\n![Graph](image://e2a745bb-fc6c-4ae3-b84f-21d3ff33b13f \"A clock with a Radium dial glowing in the dark due to Radium's radioactivity. Arma95, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nIn the last section we discussed isotopes – meaning versions of the same atoms that have differing numbers of neutrons. A nucleus will be more or less stable depending upon **its relative numbers of neutrons and protons.** In the case of radium, many isotopes, such as Ra-226, are unstable. As a result, **the atoms are prone to firing out particles to try to stabilise their nuclei.**\n\nIt is this emission of particles that is known as ‘**radiation**’, and it can be highly dangerous. There are many elements in the periodic table that are radioactive. Mostly they appear at the bottom of the table.","5c481621-852b-4a3f-be6d-0f72dfe903e8",[737],{"id":738,"data":739,"type":66,"version":24,"maxContentLevel":35},"8206e900-f9ef-4d8e-b594-a23d89aed150",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":740,"multiChoiceQuestion":744,"multiChoiceCorrect":746,"multiChoiceIncorrect":748,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":752,"matchPairsPairs":753},[741,742,743],"871b5a54-05b5-4e7e-ac4a-04e76aa8aadc","83dfd0e7-8ec9-462a-a1c4-4aea00562d21","ee17ef84-f05a-4c3c-81cd-86f1310b3c53",[745],"Which of the following is the symbol for radium?",[747],"Symbol Ra",[749,750,751],"Symbol Fe","Symbol Au","Symbol C",[143],[754],{"left":624,"right":747,"direction":35},{"id":756,"data":757,"type":25,"version":25,"maxContentLevel":35,"summaryPage":759,"introPage":767,"pages":773},"e18083d9-2690-4f41-84e7-c1a639c086a5",{"type":25,"title":758},"The Sources and Uses of Radium",{"id":760,"data":761,"type":35,"maxContentLevel":35,"version":24},"6671be77-eb54-48d0-a110-b224b53d3545",{"type":35,"summary":762},[763,764,765,766],"Radium is produced during the radioactive decay of uranium and thorium in Earth's crust","One kilogram of Earth's crust contains about 900 picograms of radium","Radium was used to make luminous paints for clocks and watches","Radium-223 is used to treat prostate cancer that has spread to bones",{"id":768,"data":769,"type":52,"maxContentLevel":35,"version":24},"32a5bc3d-60d5-4901-84fd-1e2456402f3f",{"type":52,"intro":770},[771,772],"What were the Radium Girls known for?","How did radium exposure change labor laws?",[774,811,828],{"id":775,"data":776,"type":24,"maxContentLevel":35,"version":25,"reviews":779},"d1ea9c5f-e203-45e0-9ddb-2b03c1bba622",{"type":24,"markdownContent":777,"audioMediaId":778},"Radium is produced during the radioactive decay of **uranium** and **thorium** in the Earth's crust. This natural process is responsible for the presence of radium in the environment, albeit in trace amounts. Radium undergoes radioactive decay to produce the inert gas radon.\n\nAll primordial radium originally present on Earth will have decayed already, meaning that any radium currently present is a result of ongoing radioactive decay processes.\n\n![Graph](image://13e3b552-eacc-4418-83fa-0071fe1cec87 \"A piece of uranium ore. Image: Nuclear Regulatory Commission from US, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")","8099b757-151b-4c57-bff9-2f2748430175",[780,790,800],{"id":603,"data":781,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":782,"multiChoiceQuestion":783,"multiChoiceCorrect":785,"multiChoiceIncorrect":786,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":787,"matchPairsPairs":788},[599,602,604],[784],"Which element is formed from the decay of thorium?",[624],[393,622,625],[143],[789],{"left":624,"right":611,"direction":35},{"id":604,"data":791,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":792,"multiChoiceQuestion":793,"multiChoiceCorrect":795,"multiChoiceIncorrect":796,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":797,"matchPairsPairs":798},[599,602,603],[794],"Which of the following most closely applies to uranium?",[612],[608,610,611],[143],[799],{"left":625,"right":612,"direction":35},{"id":801,"data":802,"type":66,"version":24,"maxContentLevel":35},"c29ad9bd-6440-498c-a5ee-9a9254c53b60",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":803,"multiChoiceCorrect":805,"multiChoiceIncorrect":807,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[804],"What does radium decay to produce?",[806],"Radon",[808,809,810],"Radion","Radox","Radum",{"id":812,"data":813,"type":24,"maxContentLevel":35,"version":25,"reviews":816},"821bc53b-ad9d-49ce-bcaa-048bb47fd7e1",{"type":24,"markdownContent":814,"audioMediaId":815},"Despite its decay, **radium is still present in tiny quantities in the environment**. One kilogram of Earth's crust typically contains about **900 picograms** of radium, while a liter of seawater contains around **89 femtograms**. These are incredibly tiny amounts, but it's there. Commercially, radium is typically only available in the compounds radium chloride or radium bromide due to the difficulty of isolating pure radium.\n\nUranium ores from the Democratic Republic of the Congo and Canada are the richest sources of radium today, but annual production of radium is only around **100 grams in total**.\n\nDespite its radioactivity, radium found its way into various commercial and industrial applications. The unique properties of radium, such as its radioactivity and luminescence, made it a sought-after resource in a variety of fields.","ea9ae39f-4895-4c15-9cd6-477a8939ea3f",[817],{"id":199,"data":818,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":819,"multiChoiceQuestion":820,"multiChoiceCorrect":822,"multiChoiceIncorrect":823,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":824,"matchPairsPairs":825},[195,198,200],[821],"What is the number of grams of radium produced annually?",[207],[204,206,208],[143],[826],{"left":827,"right":207,"direction":35},"Grams of radium produced annually",{"id":829,"data":830,"type":24,"maxContentLevel":35,"version":25,"reviews":833},"7c02cc86-f2ea-4c96-894f-1756b511a91e",{"type":24,"markdownContent":831,"audioMediaId":832},"Radium was once used to make luminous paints for objects such as clocks, watches, and airplane controls. The glow produced by radium made these objects visible in low light conditions, making it a useful tool for the job. However, due to the health risks associated with radium, it is now considered too hazardous to be used in this way.\n\n![Graph](image://479e657e-0e5e-40ef-a0cb-c660d86648cf \"Radium paint in a glass vial. Image by TheBeSphereOfCourse via Wikimedia Commons.\")\n\nHistorically, radium has been used in the treatment of cancer, particularly via the production of radon gas. Radium-223 is sometimes used now to treat prostate cancer that has spread to the bones. This isotope of radium emits alpha particles, which can kill cancer cells. However, in general, radium is not commonly used in modern cancer treatments due to its instability and rarity. Other more stable radioactive elements are typically used instead.","08f0261f-b78c-4a8c-b47c-429dd4314d78",[834],{"id":835,"data":836,"type":66,"version":24,"maxContentLevel":35},"d7c2d7d1-3cd2-4527-bd34-f53029607766",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":837,"activeRecallAnswers":839},[838],"What was radium once used for?",[840],"Making luminous paints for objects",{"id":842,"data":843,"type":25,"version":25,"maxContentLevel":35,"summaryPage":845,"introPage":853,"pages":859},"97ff9851-e75f-470e-aac5-282c26439529",{"type":25,"title":844},"The Hazards and Historical Impact of Radium",{"id":846,"data":847,"type":35,"maxContentLevel":35,"version":24},"f075819c-8808-4c62-8aa3-f6d3631848be",{"type":35,"summary":848},[849,850,851,852],"Radium exposure can cause cancer and damage blood, eyes, teeth, and bones","Antoine Becquerel's skin ulcerated after carrying radium for 6 hours","Radon gas from radium increases lung cancer risk when inhaled","The Radium Girls' tragedy led to better safety laws for handling radioactive materials",{"id":854,"data":855,"type":52,"maxContentLevel":35,"version":24},"ddd95563-b287-47cb-949d-9fb728656dc4",{"type":52,"intro":856},[857,858],"What health issues did the Radium Girls face from painting watch dials?","Why did Antoine Becquerel's skin ulcerate after carrying radium?",[860,878,891],{"id":861,"data":862,"type":24,"maxContentLevel":35,"version":25,"reviews":865},"00e9dbc2-dcbf-4bba-8f79-7d8caa847304",{"type":24,"markdownContent":863,"audioMediaId":864},"Radium poses a significant health hazard due to its radioactivity. Exposure to radium can increase the risk of some types of cancer, and higher doses of radium have been shown to affect the blood, eyes, teeth, and bones. \n\nThe harmful effects of radium were made clear very soon after the element’s discovery, with the first case of ‘**radium dermatitis**’. In 1910, the French scientist Antoine Becquerel carried a vial of radium in the pocket of his waistcoat for 6 hours. His skin became ulcerated as a result.\n\n![Graph](image://a04371a7-1e8e-4002-a9a6-f158ad474271 \"A portrait of Antoine Becquerel. Image :\nPaul Nadar via Wikimedia Commons\")","a9e80e70-0edf-462b-9a7e-1baeb172c274",[866],{"id":867,"data":868,"type":66,"version":24,"maxContentLevel":35},"7970c28e-7469-4f6d-a3bc-becf3c9b6fd2",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":869,"multiChoiceCorrect":871,"multiChoiceIncorrect":874,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[870],"Which of these are known effects of Radium?",[872,873],"Skin ulceration","Cancer",[875,876,877],"Chronic digestive issues","Schizophrenia","Jaundice",{"id":879,"data":880,"type":24,"maxContentLevel":35,"version":25,"reviews":883},"6015fcb4-aa5b-46a9-b9cc-a7920723057d",{"type":24,"markdownContent":881,"audioMediaId":882},"One of the decay products of radium, **radon gas**, is also a health hazard. When radon gas is inhaled, radioactive particles can get trapped in your lungs, increasing the risk of lung cancer over time. This risk is particularly high in areas with high levels of radium in the soil and rock. \n\nThe dangers of radium and its decay products have led to strict regulations on its use and disposal. These regulations are designed to protect people and the environment from the harmful effects of radium and other radioactive substances.","0a52b81b-589e-4df7-ace4-ad3082837f05",[884],{"id":885,"data":886,"type":66,"version":24,"maxContentLevel":35},"6c043d58-c929-4b2c-84a6-2ff78a1fc78b",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":887,"clozeWords":889},[888],"One of the decay products of radium, radon gas, is a health hazard that can increase the risk of lung cancer.",[890],"radon gas",{"id":892,"data":893,"type":24,"maxContentLevel":35,"version":25,"reviews":896},"507d6d22-5c2c-4305-8bad-82fea8612d5f",{"type":24,"markdownContent":894,"audioMediaId":895},"**The Radium Girls** were factory workers who contracted radiation poisoning from painting watch dials with self-luminous paint containing radium. Their story is a tragic example of the dangers of radium and the lack of safety measures in place at the time. Women at the three factories involved in the USA **were told the radium-based paint was safe**, and they even **put the brushes in their mouths** to give them a fine tip.\n\nThis practice led to the ingestion of radium, which resulted in severe health problems for these women. The symptoms experienced by the Radium Girls included anemia, bone fractures, and necrosis of the jaw. **Their experience led to significant changes in labor laws** and safety standards for workers handling radioactive materials. This tragic event serves as a stark reminder of the dangers of radium and the importance of proper safety measures when handling radioactive substances.","41d0f046-2085-4bde-bfe6-cc3d617e58a0",[897],{"id":898,"data":899,"type":66,"version":24,"maxContentLevel":35},"edac3f7c-2008-4fbc-b71d-800d7d9a943c",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":900,"activeRecallAnswers":902},[901],"Who were the Radium Girls?",[903],"Factory workers who contracted radiation poisoning",{"id":905,"data":906,"type":27,"maxContentLevel":35,"version":25,"orbs":909},"a6a209ab-6685-41ec-a213-caaa4434989b",{"type":27,"title":907,"tagline":908},"Iron","An abundant metal on earth, and a cornerstone of modern civilization.",[910,1005,1080],{"id":911,"data":912,"type":25,"version":25,"maxContentLevel":35,"summaryPage":914,"introPage":922,"pages":928},"1d403808-3c78-4ea8-8749-483b36dc103c",{"type":25,"title":913},"Introduction to Iron",{"id":915,"data":916,"type":35,"maxContentLevel":35,"version":24},"b2621cbe-0bc0-4377-8616-16f345470bec",{"type":35,"summary":917},[918,919,920,921],"Iron is the most abundant element by mass on Earth","The Iron Age marked a leap in human technology with iron tools and weapons","Iron-56 is the most common isotope, making up about 91% of natural iron","Iron's reactivity leads to rust and its ability to form magnets",{"id":923,"data":924,"type":52,"maxContentLevel":35,"version":24},"80da1125-7c10-49dc-95a0-13fc09f44987",{"type":52,"intro":925},[926,927],"What makes the Earth's inner core solid?","How does the Earth's magnetic field protect us from solar radiation?",[929,954,981],{"id":930,"data":931,"type":24,"maxContentLevel":35,"version":25,"reviews":934},"b24a226f-7e81-4edb-8613-8153e56bf00c",{"type":24,"markdownContent":932,"audioMediaId":933},"**Iron**, a transition metal, is **the most abundant element by mass on Earth**. This abundance is due to its presence in the Earth's crust, mantle, and core. It is also found in significant quantities in the sun and stars. Iron's abundance and its unique properties have made it **a vital component of life on Earth** and a key element in the development of human civilization.\n\n![Graph](image://403b9551-d0bf-4526-97c6-6fd73be7bcc1 \"Iron. Image: Public domain via Wikimedia\")\n\nThe use of iron dates back to ancient civilizations. **The Iron Age**, the final epoch in human prehistory following the Stone Age and Bronze Age, was characterized (as the name suggests) by the widespread use of iron tools and weapons. This period marked **a significant advancement in human technology and society**, as iron tools and weapons were stronger and more durable than their bronze and stone counterparts.","95482359-1025-4e16-97d5-b0362867a4bd",[935,946],{"id":936,"data":937,"type":66,"version":24,"maxContentLevel":35},"bf86f3e8-905d-4568-9aec-58881fed4db0",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":938,"multiChoiceCorrect":940,"multiChoiceIncorrect":942,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[939],"What marked the start of the Iron Age?",[941],"Use of iron tools and weapons",[943,944,945],"First digging of iron ore","The discovery of steel","The discovery that iron rusts",{"id":947,"data":948,"type":66,"version":24,"maxContentLevel":35},"12f6e15e-5962-49e5-abc5-7f57fda31027",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":949,"multiChoiceCorrect":951,"multiChoiceIncorrect":952,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[950],"What is the most common element by mass on Earth?",[907],[393,545,953],"Silicon",{"id":955,"data":956,"type":24,"maxContentLevel":35,"version":25,"reviews":959},"42e83217-38a6-424b-b9a0-da42c92bc692",{"type":24,"markdownContent":957,"audioMediaId":958},"Iron's durability and versatility have made it a crucial element in various industries. Iron alloys, such as **steel** and **cast iron**, are used extensively in modern industry. These alloys are stronger and more durable than pure iron, making them ideal for use in construction, transportation, and manufacturing.\n\n\\\nIron has **26 protons**, giving it the **atomic number 26**. It's represented by the symbol Fe.\n\nThe most common isotope of iron possesses 30 neutrons, giving it an atomic mass of 56: iron-56. In a sample of natural iron, approximately 91% of it will be iron–56. This isotope is stable and non-radioactive, making it safe for use in a variety of applications.\n\n![Graph](image://dcac8ec0-f4c9-4d37-aab2-f718383eedb1 \"The atomic structure of iron. Electron_shell_026_Iron.svg:Pumbaa (original work by Greg Robson)derivative work: Egmontaz♤ talk, CC BY-SA 2.0 UK \u003Chttps://creativecommons.org/licenses/by-sa/2.0/uk/deed.en>, via Wikimedia Commons\")","549db243-fe91-4772-808a-655ed945af9d",[960,971],{"id":200,"data":961,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":962,"multiChoiceQuestion":963,"multiChoiceCorrect":965,"multiChoiceIncorrect":966,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":967,"matchPairsPairs":968},[195,198,199],[964],"What is the number of protons in an iron nucleus?",[208],[207,206,204],[143],[969],{"left":970,"right":208,"direction":35},"Number of protons in an iron nucleus",{"id":741,"data":972,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":973,"multiChoiceQuestion":974,"multiChoiceCorrect":976,"multiChoiceIncorrect":977,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":978,"matchPairsPairs":979},[738,742,743],[975],"Which of the following is the symbol for iron?",[749],[747,750,751],[143],[980],{"left":907,"right":749,"direction":35},{"id":982,"data":983,"type":24,"maxContentLevel":35,"version":25,"reviews":986},"ff13aef9-f14b-4cfe-a31b-dc8efacf9f89",{"type":24,"markdownContent":984,"audioMediaId":985},"The atomic structure of iron contributes to its distinct properties and uses. **Iron is a silvery grey metal**, which along with some other metals such as nickel, exhibits ferromagnetism. This means **it can form magnets**, or be attracted to magnets.\n\nIn a pure state, **iron is quite reactive**, and it reacts readily with water and oxygen to form **iron oxide** (commonly known as rust). Very finely divided metallic iron is pyrophoric, meaning it can ignite spontaneously. This reactivity is due to the presence of **unpaired electrons in its outer electron shell**, which eagerly react with other elements to form compounds.\n\nIron is a significant part of the d-block in the periodic table. The d-block, also known as the transition metals, is characterized by its elements' ability to form stable, multi-valent ions. This means **it is able to form stable ions** with different electrical charges. This ability is due to the presence of unpaired electrons in their outer electron shells.\n\n![Graph](image://2690fa49-6d1e-456d-9283-739d3aacae7b \"Periodic table highlighting transition metals. Sandbh, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\n**Transition metals**, which include iron, copper, silver, and gold, serve as a bridge between the two sides of the periodic table. They are generally **hard and dense**, and **less reactive than alkali metals**, which makes them ideal for a variety of applications.\n\nIron is part of **group 8** in the periodic table, along with ruthenium, osmium, and hassium. These elements share similar properties due to their similar electron configurations. They all have high melting and boiling points, making them suitable for use in high-temperature applications.","88341d78-356f-4bdf-938a-40fe37d04c1e",[987,994],{"id":988,"data":989,"type":66,"version":24,"maxContentLevel":35},"b691f500-1c4a-440e-a198-0119dc283260",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":990,"activeRecallAnswers":992},[991],"What term refers to the ability of materials, like iron and nickel, to form magnets or be attracted to magnets?",[993],"Ferromagnetism",{"id":995,"data":996,"type":66,"version":24,"maxContentLevel":35},"d55cc2cd-4031-4d21-a8c0-fa0ad6ba5ac6",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":997,"multiChoiceCorrect":999,"multiChoiceIncorrect":1001,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[998],"Which group does iron belong to in the periodic table?",[1000],"Group 8",[1002,1003,1004],"Group 7","Group 6","Group 5",{"id":1006,"data":1007,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1009,"introPage":1017,"pages":1023},"3b6d8e25-ecee-4475-8a00-b01b78dbee76",{"type":25,"title":1008},"The Significance of Iron",{"id":1010,"data":1011,"type":35,"maxContentLevel":35,"version":24},"87e8887b-dc47-41fc-909a-df80f076bbe1",{"type":35,"summary":1012},[1013,1014,1015,1016],"Iron has been used by humans for at least 5000 years, starting with meteoric iron","Smelting iron requires temperatures above 1,250 °C, leading to stronger tools and structures","Iron is formed in dying stars and scattered into space when they explode","The Earth's core is mostly iron, creating the magnetic field that protects us from solar radiation",{"id":1018,"data":1019,"type":52,"maxContentLevel":35,"version":24},"29bfa715-c2f2-433a-9795-b67c102b3bee",{"type":52,"intro":1020},[1021,1022],"How does iron contribute to the Earth's magnetic field?","What role does iron play in the life cycle of stars?",[1024,1041,1053,1066],{"id":1025,"data":1026,"type":24,"maxContentLevel":35,"version":25,"reviews":1029},"fc2af7c4-ac2e-4cf4-bf1c-113ae4bcb573",{"type":24,"markdownContent":1027,"audioMediaId":1028},"Iron has been a crucial part of human civilization for **over 3000 years**. It is one of the **metals of antiquity**, seven metals which humans used in prehistoric times. The other metals of antiquity were gold, silver, copper, tin, lead, and mercury.\n\nThese metals were known to ancient civilizations and were used for a variety of purposes, from tools and weapons to jewelry and decoration. **The first iron used by humans came from meteorites**. Small beads of meteoric iron, shaped by hammering, have been found dating back to 3200 BCE. This suggests that humans have been using iron for at least 5000 years, and possibly even longer.\n\n![Graph](image://2ff12067-6e35-4799-a7d1-954ef9831f09 \"Iron tools from the Iron Age. Image: User:Ethan Doyle White, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")","414df67e-4eff-4ca1-a93f-34a4abeecfb1",[1030],{"id":1031,"data":1032,"type":66,"version":24,"maxContentLevel":35},"1427bd46-57c1-4c4f-afe5-9c83475cfce8",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1033,"multiChoiceCorrect":1035,"multiChoiceIncorrect":1037,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1034],"What was the source of the first iron used by humans?",[1036],"Meteorites",[1038,1039,1040],"Iron ore","Sediment in rivers","Iron forged from bronze",{"id":1042,"data":1043,"type":24,"maxContentLevel":35,"version":25,"reviews":1046},"3ca4f87a-0504-4a31-9431-16305018c5da",{"type":24,"markdownContent":1044,"audioMediaId":1045},"Due to its high melting point, smelted iron requires temperatures above 1,250 °C. The ability to smelt iron and the use of iron in the Iron Age **led to advancements in tools, weapons, and infrastructure**. This marked a significant step forward in human technology and society, as it allowed for the construction of stronger and more durable structures. \n\nIron is the sixth most abundant element in the universe. It is formed in the cores of dying stars during the process of **stellar nucleosynthesis**, where lighter elements are fused together to form heavier ones.\n\n![Graph](image://52deb4cd-597c-4911-b2d5-0b06cd3694df \"An observed supernova, occuring because the star ran out of fuel. Image: NASA, ESA, and The Hubble Heritage Team (STScI/AURA), Public domain, via Wikimedia Commons\")","5b4ded68-3efe-4194-967a-e558a305a4c0",[1047],{"id":1048,"data":1049,"type":66,"version":24,"maxContentLevel":35},"fe4ea53b-82ed-4c6d-b5cd-1c037fffb79b",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1050,"activeRecallAnswers":1052},[1051],"What is the process called where lighter elements are fused together to form heavier ones, such as iron, in the cores of dying stars?",[560],{"id":1054,"data":1055,"type":24,"maxContentLevel":35,"version":25,"reviews":1058},"58051cb6-3f5f-40a2-8998-c94c2383c849",{"type":24,"markdownContent":1056,"audioMediaId":1057},"In the late stages of a massive star’s life, it **runs out of hydrogen** to fuse in its core. The helium that remains is then fused into carbon. Once the helium runs out, progressively heavier elements are created.\n\nOnce a star’s core has turned into iron, it is no longer able to burn. **It collapses under its own gravity**, heats up to extreme temperatures and then explodes. As stars explode, iron is scattered into space. \n\nThe formation of iron in stars contributes to the elemental diversity in the universe. This iron eventually becomes part of interstellar dust and gas clouds, which can form new stars and planets.","0095e24f-a157-47e6-93fa-8bf9aee91e27",[1059],{"id":1060,"data":1061,"type":66,"version":24,"maxContentLevel":35},"f12bd550-5e79-46f5-acc0-e1bc8f8136ed",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1062,"activeRecallAnswers":1064},[1063],"What happens to iron when stars explode?",[1065],"It is scattered into space",{"id":1067,"data":1068,"type":24,"maxContentLevel":35,"version":25,"reviews":1071},"9d9b43a2-4d3e-46c6-9400-ef442072c3d3",{"type":24,"markdownContent":1069,"audioMediaId":1070},"The Earth's core is **primarily composed of iron**. The inner core, in particular, is thought to be primarily composed of an **iron-nickel alloy**. This composition is based on seismic data and the behavior of iron under extreme pressure and temperature conditions. The inner core of the Earth is subject to pressures of nearly **3.6 million atmospheres** (atm) and temperatures of around **5,200° Celsius**.\n\nUnder these extreme conditions, the iron in the core exists in a solid state, despite the high temperatures. The presence of superheated, pressurized iron in the Earth's core contributes to its **magnetic field**. The movement of this iron generates electric currents, which in turn produce the Earth's magnetic field. This magnetic field is **crucial for life on Earth**, as it protects the planet from harmful solar radiation.","f72a0e81-1979-4244-8d8b-655e8cc77cb8",[1072],{"id":1073,"data":1074,"type":66,"version":24,"maxContentLevel":35},"14f77530-a61f-4708-8187-c331523403b6",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1075,"multiChoiceCorrect":1077,"multiChoiceIncorrect":1078,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1076],"What is the Earth's core primarily composed of?",[907],[953,1079,546],"Carbon",{"id":1081,"data":1082,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1084,"introPage":1092,"pages":1098},"96eb68f6-cb8c-484a-8fa8-184ff44fe3c9",{"type":25,"title":1083},"Iron and Life",{"id":1085,"data":1086,"type":35,"maxContentLevel":35,"version":24},"743f47a9-14bd-4c13-8a17-5f59fdd95260",{"type":35,"summary":1087},[1088,1089,1090,1091],"Every living thing needs iron to survive and grow","Iron is crucial for hemoglobin in red blood cells to transport oxygen","Plants need iron for photosynthesis, which converts light into energy","Mars is red because of iron oxide, hinting at past water presence",{"id":1093,"data":1094,"type":52,"maxContentLevel":35,"version":24},"cc7de92a-b6f5-4f5a-ba5e-c7c46e836f54",{"type":52,"intro":1095},[1096,1097],"What role does iron play in the process of photosynthesis?","Why is Mars called the 'Red Planet'?",[1099,1112,1117],{"id":1100,"data":1101,"type":24,"maxContentLevel":35,"version":25,"reviews":1104},"9fec56c9-5fce-4800-b26f-ac6b4b1beb3c",{"type":24,"markdownContent":1102,"audioMediaId":1103},"**Every living thing on Earth**, from mighty redwood trees to microscopic bacteria, **needs iron to survive and grow**. Even cancer cells require iron to thrive. Iron is a vital component of **hemoglobin** in red blood cells, which is essential for transporting oxygen throughout the body. Without sufficient iron, the body cannot produce enough healthy oxygen-carrying red blood cells, leading to **iron deficiency anemia**.\n\nSymptoms of iron deficiency anemia include shortness of breath and a pale complexion. If left untreated, **iron deficiency anemia can be fatal**. This highlights the importance of maintaining adequate iron levels in the body.","c5061c97-1bad-4c71-b739-543c26889f9f",[1105],{"id":1106,"data":1107,"type":66,"version":24,"maxContentLevel":35},"6a8a55d7-2347-4733-92e6-551d67a356d2",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":1108,"clozeWords":1110},[1109],"Iron is a vital component of hemoglobin in red blood cells, essential for transporting oxygen throughout the body.",[1111],"transporting oxygen",{"id":1113,"data":1114,"type":24,"maxContentLevel":35,"version":25},"93164ad7-0b8e-4f2b-b4af-83bd9fa05122",{"type":24,"markdownContent":1115,"audioMediaId":1116},"In plants, iron is **a key constituent of chlorophyll**, which is critical to the process of photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy, which is then used to fuel the plant's activities. Without iron, this process would not be possible. \n\n![Graph](image://adc1c4b9-f8f9-4c58-b6eb-9f28d9d6d0f9 \"Potted plants receiving sunlight. Image: Public domain, Sharon Hoo via Pexels.\")\n\nIron forms a variety of compounds, including iron oxides. Iron oxides are commonly found in nature and have a variety of uses in industry. Iron oxides are **chemical compounds made of iron and oxygen**. The best known is **rust**: a form of iron oxide that occurs when iron corrodes in the presence of water or air moisture. Other iron oxides are used as pigment, as iron ores, or as catalysts to speed up reactions.\n\nPigments based on iron oxides usually produce **earthy oranges, reds, browns or blacks**. Iron oxides can even be used as a pigment in food — food coloring based on iron oxides have the E number E172 in Europe.","21fa4adb-3e7f-4c60-93b4-66153686707f",{"id":1118,"data":1119,"type":24,"maxContentLevel":35,"version":25,"reviews":1122},"1bd86360-63bf-4feb-bb1b-9bd0dde73d6c",{"type":24,"markdownContent":1120,"audioMediaId":1121},"A high concentration of iron oxide is responsible for the **characteristic red appearance of the planet Mars**. This distinctive coloring gives Mars its nickname, the '**Red Planet**'. The presence of iron oxide on Mars also suggests that there may have been water on the planet in the past. Iron is the most widely used of all the metals, accounting for 90% of all metal refined today.\n\nIts low cost and high strength make it indispensable in applications such as buildings, tools, automobiles, and in the manufacturing of steel. In manufacturing, Iron plays a crucial role, particularly in the production of steel. **Steel is a mixture of iron, small amounts of carbon, and various other metals**. The addition of other elements to iron changes its properties, making it more resistant to rust and corrosion.\n\nVarious types of steel have been developed to suit different purposes. Stainless steel, for example, contains chromium and other metals in addition to iron. It has a wide variety of uses including in the\\\nmanufacture of cutlery, surgical instruments, and jewelry.\n\n![Graph](image://d54852fa-eb0f-472c-aac2-7f3e6f63e4ae \"Surgical instruments. Image: Public domain via Freepik\")\n\nIron is used as a catalyst in the **Haber process** for producing ammonia and in the **Fischer-Tropsch process** for converting syngas (hydrogen and carbon monoxide) into liquid fuels. As a catalyst, iron speeds up these chemical reactions without being consumed in the process, making it a valuable component in these industrial processes.","b0f86f8c-bf8c-4d8d-ad93-72f0cac1ad25",[1123,1130],{"id":1124,"data":1125,"type":66,"version":24,"maxContentLevel":35},"232b9851-79c2-4d74-8558-45dd2ece84b8",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1126,"activeRecallAnswers":1128},[1127],"What gives the planet Mars its characteristic red appearance and nickname, the \"Red Planet\"?",[1129],"A high concentration of iron oxide",{"id":1131,"data":1132,"type":66,"version":24,"maxContentLevel":35},"1c1cc6bc-3a2a-4172-a03d-91d932d8f247",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1133,"multiChoiceCorrect":1135,"multiChoiceIncorrect":1137,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1134],"What percentage of all metal refined today is iron?",[1136],"90%",[1138,1139,1140],"80%","70%","65%",{"id":1142,"data":1143,"type":27,"maxContentLevel":35,"version":35,"orbs":1146},"5378e343-c871-4591-93a7-caa9de9725a8",{"type":27,"title":1144,"tagline":1145},"Gold","One of the least reactive metals, and how it has been put to use all around the world.",[1147,1243,1297],{"id":1148,"data":1149,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1151,"introPage":1159,"pages":1165},"8730d97b-4768-41f5-be5b-617a60f7440b",{"type":25,"title":1150},"Introduction to Gold",{"id":1152,"data":1153,"type":35,"maxContentLevel":35,"version":24},"08d85c5c-a6af-4384-91c6-0acd2e89b306",{"type":35,"summary":1154},[1155,1156,1157,1158],"Gold has 79 protons, giving it the atomic number 79","Gold is part of group 11, along with copper and silver","Gold is resistant to most acids but dissolves in aqua regia","Gold can be found in its natural state, often in river beds",{"id":1160,"data":1161,"type":52,"maxContentLevel":35,"version":24},"252a0bfe-dc80-41b2-a9e6-6511d12f0938",{"type":52,"intro":1162},[1163,1164],"Why is gold resistant to tarnish?","What makes gold a good choice for coinage?",[1166,1171,1195,1219],{"id":1167,"data":1168,"type":24,"maxContentLevel":35,"version":25},"a7fe2865-6bad-443a-ba0e-37a10b499766",{"type":24,"markdownContent":1169,"audioMediaId":1170},"**Gold**, a transition metal, is widely recognized for its **radiant and lustrous appearance**. This precious metal, with its unique yellow hue, has been admired and valued by civilizations throughout history. Its distinctive color and shine have made it a symbol of wealth and power, and it continues to be a sought-after material in various industries today.\n\n![Graph](image://84a5fe28-ca99-4cdc-b391-7867032f95e5 \"A gold crystal. Image: Alchemist-hp (talk) www.pse-mendelejew.de, CC BY-SA 3.0 DE \u003Chttps://creativecommons.org/licenses/by-sa/3.0/de/deed.en>, via Wikimedia Commons\")\n\nThe use of gold in jewelry has long been prevalent due to its aesthetic appeal. The oldest gold artifacts in the world, small beads found in Bulgaria, date back to some time between 4200 and 4600 BCE. This demonstrates the **long-standing human fascination with this metal**. Its malleability and resistance to tarnish have made it an **ideal material for crafting intricate and enduring pieces of jewelry**.","fa1b0c8f-2d7e-4b62-95ad-0479deab2819",{"id":1172,"data":1173,"type":24,"maxContentLevel":35,"version":25,"reviews":1176},"ec9c911b-4c06-41e3-9dc2-8fc04320452f",{"type":24,"markdownContent":1174,"audioMediaId":1175},"The traditional alchemical symbol for gold is **a sun symbol**, and much of the mythology around gold relates to the sun. This association with the sun, a source of light and life, further underscores the cultural significance of gold. It has been revered not just for its physical properties, but also for its symbolic meanings.\n\nGold is characterized by having **79 protons** in its atomic structure, giving it the **atomic number 79**. It's represented by the symbol Au, derived from the Latin word for gold, '**aurum**'. Its atomic structure gives gold its unique properties, including its high density and malleability.\n\nThe only stable isotope of gold contains **118 neutrons**, giving it an atomic mass of 197. This isotope, **Gold-197**, makes up all naturally occurring gold. Its stability contributes to gold's resistance to corrosion and tarnish, making it a durable material for various applications.","9eb591a0-74ba-4675-a6d7-ebc0fbc1d98f",[1177],{"id":1178,"data":1179,"type":66,"version":24,"maxContentLevel":35},"fb3fc3d2-5cd9-42ba-a4d9-938737842d4b",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1180,"multiChoiceQuestion":1184,"multiChoiceCorrect":1186,"multiChoiceIncorrect":1188,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1191,"matchPairsPairs":1192},[1181,1182,1183],"f9ac542a-e997-4481-8da2-cb74e1dfdbc3","7d4402ca-c9d8-4fa5-bb23-87c4b5a4515b","8491ad43-3ce8-48ef-9432-f1fd6306cfe2",[1185],"What is the number of protons in gold's atomic structure?",[1187],"79",[1189,1190,206],"33","15",[143],[1193],{"left":1194,"right":1187,"direction":35},"Number of protons in gold's atomic structure",{"id":1196,"data":1197,"type":24,"maxContentLevel":35,"version":25,"reviews":1200},"030a5180-4169-4366-9d01-bb213abc0b30",{"type":24,"markdownContent":1198,"audioMediaId":1199},"Gold is chemically unreactive, but will dissolve in a mixture of nitric and hydrochloric acids called **aqua regia**. This property of gold, its resistance to most acids but solubility in aqua regia, was historically used as a test for gold purity. Today, it continues to be a significant way of determining gold's utility and value.\n\n![Graph](image://9f15d2d0-7f83-4765-a3e6-e14d69720d43 \"A bar of gold being dissolved in a test tube filled with acid (aqua regia). Image: Daniel Grohmann, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nGold is a member of the **transition metals**, found in the d-block of the periodic table. These metals are known for their high melting points, high densities, and ability to form stable ions. Gold shares these characteristics, making it a typical representative of the transition metals.\n\n![Graph](image://88ef18dc-117f-4811-b357-4fd7dcff68f1 \"The first row of transition metals. Image: Keresluna via Wikimedia\")\n\nGold is part of **group 11** of the periodic table, along with the metals copper and silver and the synthetic radioactive element roentgenium. This group contains relatively **inert, corrosion-resistant metals**. These shared properties have led to the use of these metals in similar applications, such as coinage and jewelry.","03cdb797-7923-4b0e-afed-f5da1c83eac1",[1201,1212],{"id":1202,"data":1203,"type":66,"version":24,"maxContentLevel":35},"d6175b0b-8ee2-4cdd-bee3-12d048042ae2",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1204,"multiChoiceCorrect":1206,"multiChoiceIncorrect":1208,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1205],"What is the atomic mass of gold's only stable isotope?",[1207],"197",[1209,1210,1211],"199","167","203",{"id":1213,"data":1214,"type":66,"version":24,"maxContentLevel":35},"8db54248-f398-4034-ae2c-9d19fce0d35e",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1215,"activeRecallAnswers":1217},[1216],"What can dissolve gold?",[1218],"Aqua regia",{"id":1220,"data":1221,"type":24,"maxContentLevel":35,"version":25,"reviews":1224},"46564ae6-5ceb-43c0-a3cf-deef7bbfd13c",{"type":24,"markdownContent":1222,"audioMediaId":1223},"Group 11 is also known as **the coinage metals**, as gold, silver, and copper have all been used in minting coins. It is likely these three metals were the first three elements discovered. Their discovery and use in early coinage marked a significant development in human civilization, enabling trade and economic growth.\n\n![Graph](image://d20765fa-ccd3-4e61-8f2b-43837f039404 \"An ancient gold coin. Image: Metropolitan Museum of Art, CC0, via Wikimedia Commons\")\n\nGold is one of the few elements that **can be found in a natural state**. Unlike many other elements, it can be found in its elemental form in nature, often in nuggets or grains in rocks, veins, and alluvial deposits (material deposited by rivers). This natural occurrence has made gold accessible to humans since prehistoric times.\n\nNatural gold is often discovered in **river beds** and **alluvial deposits**, where it can be extracted by panning for gold. This method of gold extraction, while labor-intensive, has been used for thousands of years and continues to be used today, particularly by small-scale miners.\n\nThere is about **4g of gold in every 1000000 tonnes of seawater**. While this concentration is too low for economical extraction, it illustrates the widespread distribution of gold on Earth. Gold can be found not only in terrestrial sources but also in the oceans, albeit in minute quantities.","1ad4b605-70c8-42b5-a480-f8395b8a3bb8",[1225,1236],{"id":1226,"data":1227,"type":66,"version":24,"maxContentLevel":35},"01947a3b-cfcc-45c5-b0d4-a8c054c023c4",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1228,"multiChoiceCorrect":1230,"multiChoiceIncorrect":1232,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1229],"What group of the periodic table, also known as the coinage metals, does gold belong to?",[1231],"Group 11",[1233,1234,1235],"Group 9","Group 10","Group 12",{"id":1237,"data":1238,"type":66,"version":24,"maxContentLevel":35},"ca6126d8-f96a-438f-a860-ef794f5d4ddc",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1239,"activeRecallAnswers":1241},[1240],"What is the method of gold extraction from river beds and alluvial deposits which has been used for thousands of years?",[1242],"Panning for gold",{"id":1244,"data":1245,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1247,"introPage":1255,"pages":1261},"0ae8b7ab-4162-4e30-9c16-f74fdc75dba9",{"type":25,"title":1246},"History and Economic Significance of Gold",{"id":1248,"data":1249,"type":35,"maxContentLevel":35,"version":24},"e8bb5fa9-9f4c-47f8-9e67-75365e3a92a1",{"type":35,"summary":1250},[1251,1252,1253,1254],"Gold coins were first made in Lydia around 600 BCE","Gold is rare, unreactive, and easy to work with, making it ideal for coinage","The gold standard fixed currency values to gold but is now mostly abandoned","Gold is a 'safe haven' asset during economic instability",{"id":1256,"data":1257,"type":52,"maxContentLevel":35,"version":24},"bc941db0-e290-4a77-b51c-92ac25450d2b",{"type":52,"intro":1258},[1259,1260],"How did gold coins from Lydia change ancient trade?","Why is gold considered a 'safe haven' during economic instability?",[1262,1267,1284],{"id":1263,"data":1264,"type":24,"maxContentLevel":35,"version":25},"da44d5e7-0445-466e-b554-d482125b907c",{"type":24,"markdownContent":1265,"audioMediaId":1266},"Gold has been used by humans for thousands of years for various purposes. Its natural beauty, durability, and rarity have made it a valuable resource throughout history. From ancient civilizations to modern societies, gold has played a significant role in human culture and economy.\n\nHistorically, gold has been used as **a form of currency**, due to its stable nature, and for **ornamentation**, due to its attractive, shiny appearance. Its use as a medium of exchange dates back to ancient times, and its role in ornamentation is evident in the rich history of gold jewelry and decorative arts.\n\nGold’s stability has made it a cornerstone of the development of human economies. More than any other commonly found substance on earth, **gold is unreactive**, meaning it won’t degrade or oxidise over time. For centuries, this has made it a useful way for people to store value.","81b886b6-7582-4472-8acc-f4e3f8867a8b",{"id":1268,"data":1269,"type":24,"maxContentLevel":35,"version":25,"reviews":1272},"dde99c17-e67b-4cf3-a3f2-49b8e8773561",{"type":24,"markdownContent":1270,"audioMediaId":1271},"The first known coins containing gold were made in Lydia around 600 BCE. This marked a significant development in the use of gold, establishing it as **a standard for monetary exchange**. These early gold coins facilitated trade and commerce, contributing to the growth and prosperity of ancient civilizations.\n\n![Graph](image://276974cb-9128-4018-beda-1640a6ec1efd \"The Lydia Coin. Image: Classical Numismatic Group, Inc. http://www.cngcoins.com, CC BY-SA 3.0 \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nGold is useful for coinage as it is rare and thus valuable, chemically unreactive, doesn't corrode easily and is malleable and easy to work with. These properties have made gold a reliable and desirable material for coinage throughout history. Even today, **many countries continue to mint gold coins**, although these are typically intended for collectors or investors rather than for circulation.","36c4bfd7-e483-49df-a062-13bb83631f46",[1273],{"id":1274,"data":1275,"type":66,"version":24,"maxContentLevel":35},"9cc66cc0-c39e-4058-9da7-509bcf6420f0",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1276,"multiChoiceCorrect":1278,"multiChoiceIncorrect":1280,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1277],"Where were the first known coins containing gold made?",[1279],"Lydia",[1281,1282,1283],"Ithaca","Mesopotamia","Babylon",{"id":1285,"data":1286,"type":24,"maxContentLevel":35,"version":25,"reviews":1289},"d71acc9c-128f-417c-a433-3ed14bf9bc3d",{"type":24,"markdownContent":1287,"audioMediaId":1288},"A gold standard is a monetary system which **fixes the value of currencies in terms of a specified amount of gold**. At one stage, the gold standard was widespread across the globe, but the gold standard has now largely been abandoned. Despite this, the concept of the gold standard has had a profound impact on global economic systems and **continues to be a topic of debate among economists**.\n\n![Graph](image://ed14efad-8744-4b77-aa4a-ce5fafc0cb1e \"Gold bars with banknotes and coins. Image: Public domain via Unsplash\")\n\nInvestors often turn to gold during economic instability due to its enduring value. Unlike paper currency or other assets, **gold retains its intrinsic value** and is not subject to inflation or devaluation. This has led to its reputation as a '**safe haven**' asset, providing a measure of financial security in uncertain times.","0bb2ebcd-3f4e-452a-9069-18406f7f7570",[1290],{"id":1291,"data":1292,"type":66,"version":24,"maxContentLevel":35},"7134bf36-b34a-4b22-9dd9-2bd805760f03",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1293,"activeRecallAnswers":1295},[1294],"What is the term for a monetary system which fixes the value of currencies in terms of a specified amount of gold?",[1296],"Gold standard",{"id":1298,"data":1299,"type":25,"version":35,"maxContentLevel":35,"summaryPage":1301,"introPage":1309,"pages":1315},"2f8d85e1-5364-491d-9093-8cef21c61982",{"type":25,"title":1300},"Uses for Gold",{"id":1302,"data":1303,"type":35,"maxContentLevel":35,"version":24},"5c99f56b-3501-4d09-a2ce-5b31a3f82146",{"type":35,"summary":1304},[1305,1306,1307,1308],"Gold electroplating adds a corrosion-resistant, decorative layer to metals","Gold nanoparticles speed up chemical reactions without being consumed","Gold nanoparticles are being researched for targeted cancer treatments","Modern gold mining methods can harm the environment and human rights",{"id":1310,"data":1311,"type":52,"maxContentLevel":35,"version":24},"7123c493-f7e9-480b-860f-5e02e172fac5",{"type":52,"intro":1312},[1313,1314],"What makes carbon a non-metal in group 14?","How does carbon's electron configuration let it form four bonds?",[1316,1332,1345,1350],{"id":1317,"data":1318,"type":24,"maxContentLevel":35,"version":25,"reviews":1321},"da0fe758-67e1-4348-9544-8cc89d6d4ff6",{"type":24,"markdownContent":1319,"audioMediaId":1320},"Electroplating with gold provides a **corrosion-resistant decorative layer** on other metals. This process involves the deposition of a thin layer of gold onto the surface of another metal, typically to enhance its appearance, prevent tarnishing, or reduce friction. Gold electroplating is commonly used in a variety of industries, including **electronics**, **aerospace**, and **jewelry**.\n\nIn electronics, gold's **excellent conductivity** and **resistance to corrosion** make it ideal for coating connectors and other components. In jewelry, gold electroplating is used to give pieces a gold appearance at a fraction of the cost of solid gold.\n\n![Graph](image://7a4cbfab-aa36-49a4-87ff-3ef90f5406a2 \"Gold electroplated jewelry. Image: Public domain via Pexels\")","b660ebc0-1960-4452-8769-6fae8a77b0a8",[1322],{"id":742,"data":1323,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1324,"multiChoiceQuestion":1325,"multiChoiceCorrect":1327,"multiChoiceIncorrect":1328,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1329,"matchPairsPairs":1330},[738,741,743],[1326],"Which of the following is the symbol for gold?",[750],[747,749,751],[143],[1331],{"left":1144,"right":750,"direction":35},{"id":1333,"data":1334,"type":24,"maxContentLevel":35,"version":25,"reviews":1337},"16a61ce4-8645-47b8-ab65-9218e34777b6",{"type":24,"markdownContent":1335,"audioMediaId":1336},"The process of gold electroplating involves passing an electric current through a solution containing gold ions. This results in gold being deposited onto the **cathode** (negative electrode). The thickness of the gold layer can be controlled by adjusting the duration and intensity of the electric current, allowing for precise control over the electroplating process.\n\nGold nanoparticles (tiny particles of gold) are used as **catalysts** in various chemical reactions, speeding up the reactions without being consumed in the process. These nanoparticles, which can be as small as **a few nanometers** in diameter, have unique properties that differ from those of bulk gold, making them useful in a variety of applications.","33b1ff05-727f-4914-bdb4-c2d2fece9730",[1338],{"id":1339,"data":1340,"type":66,"version":24,"maxContentLevel":35},"4bda0503-48c9-4765-a3df-519cad3738f5",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1341,"activeRecallAnswers":1343},[1342],"How does the process of gold electroplating work?",[1344],"Passing an electric current through a solution containing gold ions",{"id":1346,"data":1347,"type":24,"maxContentLevel":35,"version":35},"7a0755a4-9837-4e5e-af48-05b0941adf6c",{"type":24,"markdownContent":1348,"audioMediaId":1349},"**Vinyl acetate**, used to make PVA , glue, paint and resin, is produced using a gold catalyst. The use of gold nanoparticles in this process improves the efficiency of the reaction, resulting in higher yields of vinyl acetate. This is just one example of how gold nanoparticles are used in industrial chemistry.\n\n![Graph](image://070070ae-cd1c-42d2-b1c2-eb5812e2d838 \"A bucket of paint. Image: Pavel Danilyuk, Public Domain via Pexels.\")\n\nThe potential of gold nanoparticles in **treatments for cancer** is currently being researched. Due to their small size and unique properties, gold nanoparticles can be used to target cancer cells specifically, potentially reducing the side effects of traditional cancer treatments. While this research is still in its early stages, it highlights the potential of gold nanoparticles in medicine.","d0ab25f3-9597-4b2f-a88b-965c18317f75",{"id":1351,"data":1352,"type":24,"maxContentLevel":35,"version":25},"7577708e-5180-4653-9f35-9ffa69637d9a",{"type":24,"markdownContent":1353,"audioMediaId":1354},"Gold mining could be at least **7000 years old**. Romans used hydraulic mining methods on a large scale to extract gold from alluvial deposits. This historical practice of gold mining has evolved over the centuries, with modern techniques allowing for the extraction of gold from a variety of sources.\n\n![Graph](image://9b9f4461-7e81-4edf-9e10-093d84415981 \"Hard rock mining.\")\n\nCommon methods of gold mining used today include **hard rock mining** and **by-product gold mining**. Hard rock mining involves extracting gold from solid rock, while by-product mining involves extracting gold from the waste materials of other mining operations. Both methods require significant resources and can have substantial environmental impacts.\n\nThe process of gold mining often involves the use of harmful chemicals like **cyanide**, leading to environmental degradation. Human rights and environmental issues are a cause of frequent concern in the gold-mining industry. The extraction of gold can result in **soil erosion**, **loss of biodiversity**, and **contamination of water sources**, highlighting the need for sustainable mining practices.","2f05587e-50c0-40d0-a8ba-3d6b430ef522",{"id":1356,"data":1357,"type":27,"maxContentLevel":35,"version":35,"orbs":1359},"e3fe9bbc-b635-4b99-8770-6bf63f7b984b",{"type":27,"title":1079,"tagline":1358},"The life element - what we are all made of.",[1360,1435,1494],{"id":1361,"data":1362,"type":25,"version":35,"maxContentLevel":35,"summaryPage":1364,"introPage":1372,"pages":1378},"29913d9b-f5a9-42fc-974a-f10ba9256c7b",{"type":25,"title":1363},"Introduction to Carbon",{"id":1365,"data":1366,"type":35,"maxContentLevel":35,"version":24},"bcc90ff9-786c-4a0b-bad1-1e9a790537a8",{"type":35,"summary":1367},[1368,1369,1370,1371],"Carbon can form long chains, creating diverse organic compounds","Diamonds and graphite are pure carbon forms with different properties","Carbon-12 is the most common isotope, crucial for radiocarbon dating","Carbon forms four covalent bonds, making it super versatile",{"id":1373,"data":1374,"type":52,"maxContentLevel":35,"version":24},"13b22d5f-c4c3-4ee4-b1f1-e89319715c93",{"type":52,"intro":1375},[1376,1377],"Why is carbon able to form so many different compounds?","What makes diamonds and graphite so different?",[1379,1392,1408,1430],{"id":1380,"data":1381,"type":24,"maxContentLevel":35,"version":25,"reviews":1384},"f99e18d9-194f-411f-a5da-8febe3996adf",{"type":24,"markdownContent":1382,"audioMediaId":1383},"**Carbon** is essential to life on Earth. This is largely due to its unique ability to form long chain molecules. These chains, which can be linear or branched, allow carbon to form **a vast array of complex structures**. This property is the basis for the diversity of organic compounds, which include everything from simple gases like methane to complex biomolecules like proteins and DNA.\n\n![Graph](image://bb9dd87a-2991-43fc-abee-14bca6dd1e95 \"Precious red diamonds. Image: via Freepik.\")\n\nThe significance of carbon is further underscored by the fact that an entire branch of chemistry is devoted to the study of compounds that contain carbon. This branch, known as **organic chemistry**, is a major field of study in both academic and industrial settings.","0f521aa1-6556-4b92-8321-d2e5dddaf3b3",[1385],{"id":1386,"data":1387,"type":66,"version":24,"maxContentLevel":35},"9b545ec3-8c28-43d8-8555-b7a60bb6f636",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1388,"activeRecallAnswers":1390},[1389],"What branch of chemistry is devoted to the study of compounds that contain carbon?",[1391],"Organic chemistry",{"id":1393,"data":1394,"type":24,"maxContentLevel":35,"version":25,"reviews":1397},"38621004-815f-49d5-8c8e-c39c1f966ddb",{"type":24,"markdownContent":1395,"audioMediaId":1396},"Pure carbon exists in several different physical forms, including **diamonds** and **graphite**. These forms, known as **allotropes**, have different physical properties due to the different ways in which the carbon atoms are bonded together.\n\nFor example, diamonds are extremely hard and have a high refractive index. This high refractive index is responsible for diamonds’ brilliant sparkle. Graphite, on the other hand, is soft, slippery, and has a high electrical conductivity.\n\nCarbon is the sixth element in the periodic table, which means it has **six protons** in its atomic nucleus. This gives it an **atomic number of six**.\n\n![Graph](image://e2a2a619-0b1b-4103-8c5d-25c798622639 \"An electron shell diagram for carbon. Image: Greg Robson, CC BY-SA 2.0 UK \u003Chttps://creativecommons.org/licenses/by-sa/2.0/uk/deed.en>, via Wikimedia Commons\")","2f357273-ebd2-44f8-b73e-c8a338773dad",[1398],{"id":743,"data":1399,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1400,"multiChoiceQuestion":1401,"multiChoiceCorrect":1403,"multiChoiceIncorrect":1404,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1405,"matchPairsPairs":1406},[738,741,742],[1402],"Which of the following is the symbol for carbon?",[751],[747,749,750],[143],[1407],{"left":1079,"right":751,"direction":35},{"id":1409,"data":1410,"type":24,"maxContentLevel":35,"version":25,"reviews":1413},"b03678b3-c75f-449f-9379-deee481d618f",{"type":24,"markdownContent":1411,"audioMediaId":1412},"The most common isotope of carbon is **carbon-12**, which has six neutrons in addition to its six protons. This gives it an atomic mass of 12. Other isotopes of carbon include carbon-13 and carbon-14, which have seven and eight neutrons respectively. These isotopes are less common than carbon-12, but they are important in certain applications, such as radiocarbon dating.\n\nThe atomic structure of carbon allows it to form **four covalent bonds with other atoms**. This is due to the fact that carbon has four electrons in its outermost shell, which can be shared with other atoms to form stable covalent bonds. This property is the basis for carbon's ability to form a wide variety of compounds, including both organic and inorganic compounds.\n\nCarbon is part of the p-block of the periodic table. This block includes elements that have their outermost electron in a p orbital. The term **orbital** refers to a region of space around the nucleus of an atom where there is a high probability of finding an electron. The p orbital has a distinctive shape, consisting of six lobed shapes that emanate from a central point at evenly spaced angles.\n\n![Graph](image://d7e98b33-d424-41b0-ad60-5dc5002d980f \"The p sublevel group of the Periodic Table (in the blue square). Image: Cdang and Adrignola, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")","f44b422f-1856-44e1-9fb8-038483a545f1",[1414,1423],{"id":1415,"data":1416,"type":66,"version":24,"maxContentLevel":35},"004970fb-4106-4374-9ab6-bc6395609d91",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1417,"multiChoiceCorrect":1419,"multiChoiceIncorrect":1421,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1418],"How many covalent bonds can carbon form with other atoms?",[1420],"4",[1422,204,206],"5",{"id":1424,"data":1425,"type":66,"version":24,"maxContentLevel":35},"ca0b43e2-612b-42d5-b3c2-637cc714b6f6",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1426,"activeRecallAnswers":1428},[1427],"What is the most common isotope of Carbon?",[1429],"Carbon-12",{"id":1431,"data":1432,"type":24,"maxContentLevel":35,"version":35},"7ddaef1e-d90e-4385-87a6-492436c57922",{"type":24,"markdownContent":1433,"audioMediaId":1434},"The p-block of the periodic table is unique in that it contains all three types of elements: **metals**, **non-metals**, and **metalloids**. Metalloids, also known as semi-metals, are elements that have properties intermediate between those of metals and non-metals. Carbon, a non-metal, is located in the upper left of the p-block.\n\nCarbon is part of **group 14** in the periodic table, along with **silicon**, **germanium**, **tin**, and **lead**. These elements are known as **the carbon group** or the tetrels. Like carbon, all of these elements can form four chemical bonds, which is the most of any group in the periodic table. This property is due to the fact that they have four electrons in their outermost shell.","916fedf4-a995-4caa-818d-db39732e7b48",{"id":1436,"data":1437,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1439,"introPage":1447,"pages":1453},"cbe8e3ac-4ed2-4282-8795-4f321fe30cc7",{"type":25,"title":1438},"Forms and Properties of Carbon",{"id":1440,"data":1441,"type":35,"maxContentLevel":35,"version":24},"40bbf76b-dcfd-4108-8c6e-a5d93b6ffcdf",{"type":35,"summary":1442},[1443,1444,1445,1446],"Carbon exists in different forms called allotropes, like graphite and diamond","Diamond is the hardest material, while graphite is soft and used in pencils","Fullerenes are carbon structures shaped like spheres or cylinders, discovered in 1985","Fossil fuels, made of hydrocarbons, powered the industrial revolution but drive climate change",{"id":1448,"data":1449,"type":52,"maxContentLevel":35,"version":24},"a9eef90c-cf3f-47b4-8a05-fa726a83f47d",{"type":52,"intro":1450},[1451,1452],"How does carbon-14 dating determine the age of ancient artifacts?","What is the significance of half-life in carbon-14 dating?",[1454,1459,1464,1484],{"id":1455,"data":1456,"type":24,"maxContentLevel":35,"version":25},"48d78696-debe-4956-8fea-a6865ba1c4c9",{"type":24,"markdownContent":1457,"audioMediaId":1458},"Carbon can exist in several pure forms, known as **allotropes**. These include **graphite**, **diamond**, and **fullerenes**. Each allotrope has a unique structure, which gives it distinct physical and chemical properties.\n\nGraphite and diamond are two of the most common allotropes of carbon. Despite being composed of the same element, they have very different properties due to the different ways in which their carbon atoms are arranged.\n\nDiamond is **colorless, transparent, and the hardest known material**, making it valuable for both industrial applications and jewelry. Graphite, on the other hand, is **black, shiny, and soft**. It is used in a variety of applications, including pencils and lubricants.\n\n![Graph](image://a0dba0fc-d656-4017-b325-5a2678a01047 \"A model of buckminsterfullerene, showing the spherical arrangement of the carbon atoms. Image: Wing-Chi Poon via Wikimedia\")","1eb9e4f6-b068-4cf1-b0d5-1d90877f6abc",{"id":1460,"data":1461,"type":24,"maxContentLevel":35,"version":25},"a392c7fc-4878-439b-906c-9643b9268c83",{"type":24,"markdownContent":1462,"audioMediaId":1463},"**Fullerenes** are a more recently discovered form of carbon. They have a unique structure, consisting of hexagonal rings of carbon atoms arranged in a spherical or cylindrical shape. This gives them unique properties that make them useful in a variety of scientific and industrial applications. The first fullerenes were discovered in 1985 and named **buckminsterfullerene** — though this is often shortened as **buckyballs**.\n\nThe ability of carbon to form chains and rings is a key factor in the diversity of organic compounds. These structures, which can be simple or complex, are the basis for the vast array of organic compounds that exist.\n\nCarbon is a key component of many essential biological molecules, including **carbohydrates**, **proteins**, and **fats**. These molecules play crucial roles in the structure, function, and regulation of the body's tissues and organs. For example, proteins are used for structural support, transport of substances, and catalyzing biochemical reactions, while carbohydrates provide energy and regulate various bodily processes.","a84b6458-85af-457d-95ad-a2e177dd4871",{"id":1465,"data":1466,"type":24,"maxContentLevel":35,"version":25,"reviews":1469},"70e64f23-0d27-402a-aab3-73f5a1bcab82",{"type":24,"markdownContent":1467,"audioMediaId":1468},"![Graph](image://943eaec5-5adc-4ba1-93f7-6505af95ec1c \"A model of a DNA molecule, showing the double helix structure and the sugar-phosphate backbone. Image: Mstroeck at English Wikipedia, CC BY-SA 3.0 \u003Chttp://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons\")\n\nThe ability of carbon to form long chains is particularly important in the formation of **DNA molecules**. DNA, or deoxyribonucleic acid, is a molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses.\n\nThe backbone of the DNA molecule is a **chain of sugars and phosphate groups**, the former of which are molecules based on carbon. The structure of DNA allows it to **carry vast amounts of information**, which can then be replicated to create new cells and new life.","346e0d82-f4dd-4ce8-b386-03c530d38c86",[1470,1477],{"id":1471,"data":1472,"type":66,"version":24,"maxContentLevel":35},"30d8a7a8-fb4f-48d5-a96a-18104b2fa53c",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1473,"activeRecallAnswers":1475},[1474],"What is a key factor in the diversity of organic compounds?",[1476],"Carbon's ability to form chains and rings",{"id":1478,"data":1479,"type":66,"version":24,"maxContentLevel":35},"ab2f9b67-9565-4271-b989-437f20d14b06",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1480,"activeRecallAnswers":1482},[1481],"What are hydrocarbons?",[1483],"Compounds of carbon and hydrogen",{"id":1485,"data":1486,"type":24,"maxContentLevel":35,"version":25,"reviews":1489},"7c9243ad-05f7-4817-9f05-9bb8e44ddc37",{"type":24,"markdownContent":1487,"audioMediaId":1488},"**Hydrocarbons**, which are compounds composed solely of carbon and hydrogen, have played a crucial role in human development. They have been particularly important as fuels, providing energy for a wide range of human activities.\n\n**Fossil fuels**, which are a type of hydrocarbon, have played a significant role in the advancement of human society. These include **coal**, **oil**, and **natural gas**, which powered the industrial revolution and continue to be a major source of energy today. The use of these fuels has enabled a wide range of technological advancements and has **significantly increased the standard of living in many parts of the world**.\n\n![Graph](image://25a9eaae-c392-4129-a6f6-17e89d6b1814 \"Coal, an example of a fossil fuel. Image: Amcyrus2012 via Wikimedia\")\n\nDespite their benefits, the use of fossil fuels is now known to be **a major driver of climate change**. This is due to the fact that burning these fuels releases **carbon dioxide**, a greenhouse gas, into the atmosphere.\n\nDespite their environmental impact, **hydrocarbons remain a key energy source** due to their high energy density and abundance.","ddcb29d2-090b-4dae-a5a8-36d584419920",[1490],{"id":1478,"data":1491,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1492,"activeRecallAnswers":1493},[1481],[1483],{"id":1495,"data":1496,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1498,"introPage":1506,"pages":1512},"22fab86c-a53d-4dd5-9239-9f6117a4b64c",{"type":25,"title":1497},"Carbon and Its Impact",{"id":1499,"data":1500,"type":35,"maxContentLevel":35,"version":24},"2e829ba9-b0f3-43c7-9e24-797cee86ea09",{"type":35,"summary":1501},[1502,1503,1504,1505],"Human activities have increased atmospheric carbon dioxide levels by 50% since the pre-industrial era","Carbon nanotubes are tiny cylinders with super strength and high thermal conductivity","Carbon-14 dating can determine the age of artifacts up to 50,000 years old","Carbon-14 decays into nitrogen-14 with a half-life of 5,730 years",{"id":1507,"data":1508,"type":52,"maxContentLevel":35,"version":24},"f3d0d4e2-dcf1-4a5a-abf1-94460385e417",{"type":52,"intro":1509},[1510,1511],"Who isolated arsenic in the Middle Ages?","Why was arsenic used in pigments despite its toxicity?",[1513,1537,1550],{"id":1514,"data":1515,"type":24,"maxContentLevel":35,"version":25,"reviews":1518},"d9256adb-b395-44a0-940c-8da0a45da2ac",{"type":24,"markdownContent":1516,"audioMediaId":1517},"The increase in atmospheric carbon dioxide levels due to human activities is **a major driver of global warming and climate change**. This is because carbon dioxide is a greenhouse gas, which means it traps heat in the atmosphere and contributes to the greenhouse effect. Atmospheric carbon dioxide concentrations have increased significantly since the pre-industrial era.\n\n![Graph](image://561eb066-c98c-416d-bb75-c45d21716727 \"A coal-fired power station. Image: Joel200716, CC BY 4.0 \u003Chttps://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons\")\n\nThey are now **50% higher** than pre-industrial levels, having increased from 280 parts per million (ppm) to 421 ppm as of May 2022. This increase **is largely due to human activities**, particularly the burning of fossil fuels and deforestation. Efforts to mitigate climate change largely focus on **reducing carbon dioxide emissions**. This can be achieved through a variety of means, including transitioning to renewable energy sources, improving energy efficiency, and implementing carbon capture and storage technologies.","1080263b-10e2-4bf8-a562-eb498c08ae6f",[1519,1530],{"id":1520,"data":1521,"type":66,"version":24,"maxContentLevel":35},"1bf9aeb3-2705-4213-90ec-e64280864aff",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1522,"multiChoiceCorrect":1524,"multiChoiceIncorrect":1526,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1523],"How much have atmospheric carbon dioxide concentrations increased since the pre-industrial era?",[1525],"50%",[1527,1528,1529],"100%","150%","25%",{"id":1531,"data":1532,"type":66,"version":24,"maxContentLevel":35},"3738966b-8e34-40fb-8c7d-f3847b423749",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1533,"activeRecallAnswers":1535},[1534],"What term refers to the phenomenon where gases like carbon dioxide trap heat in the atmosphere, contributing to global warming and climate change?",[1536],"The greenhouse effect",{"id":1538,"data":1539,"type":24,"maxContentLevel":35,"version":25,"reviews":1542},"15061196-38c8-4afb-acc9-e2965d575c64",{"type":24,"markdownContent":1540,"audioMediaId":1541},"**Carbon nanotubes** are a form of carbon in which the atoms are arranged in a cylindrical structure. These structures have diameters in the range of nanometers, making them one of the smallest materials known to science. Carbon nanotubes exhibit a range of remarkable properties, including very high tensile strength and thermal conductivity. Some types of carbon nanotubes are also good at **conducting electricity**, while others are **semiconductors**.\n\nThese properties are due to the unique structure of the nanotubes, which results in a **high surface area and strong interatomic bonds**. Due to their unique electrical and mechanical properties, carbon nanotubes are being explored for use in a variety of applications. These range from electronics to materials science. \n\nFor example, they are used in the manufacture of vantablack, an **ultra-absorptive black paint**. Other potential applications for carbon nanotubes include the production of **high-strength fabrics** and **biosensors** for biomedical and agricultural applications.","24abe74d-efc1-47e1-8d38-c527cce02ace",[1543],{"id":1544,"data":1545,"type":66,"version":24,"maxContentLevel":35},"9d965b91-5ccf-4f0b-8684-a34753dde4e7",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1546,"activeRecallAnswers":1548},[1547],"What term is used for a form of carbon where the atoms are arranged in a cylindrical structure, and which exhibit properties like high tensile strength, thermal conductivity, and in some cases, good electrical conductivity?",[1549],"Carbon nanotubes",{"id":1551,"data":1552,"type":24,"maxContentLevel":35,"version":25,"reviews":1555},"12fbd97f-b4b8-4e14-8ae4-13a0c8ad658a",{"type":24,"markdownContent":1553,"audioMediaId":1554},"**Carbon-14**, a radioactive isotope of carbon, is used in a technique known as carbon dating. This technique is used to determine the age of ancient artifacts and fossils, providing valuable information about the history of life on Earth. The technique of carbon dating has revolutionized the field of archaeology. It typically allows scientists to determine the age of objects up to 50,000 years old, providing a window into the past that was previously inaccessible.\n\nCarbon-14 has a half-life of 5,730 years, which means that half of a given sample of carbon-14 will have decayed into nitrogen-14 after this time. \n\nThis property is used in **carbon dating** to estimate the age of organic artifacts. By measuring the amount of carbon-14 remaining in a sample and comparing it to the expected amount based on the half-life, scientists can estimate the time that has elapsed since the death of the organism from which the sample was taken. Carbon dating has been instrumental in dating ancient artifacts and understanding the timeline of human history.","bddd43a0-a7c9-40e1-abab-48a6738de34f",[1556],{"id":1557,"data":1558,"type":66,"version":24,"maxContentLevel":35},"eff60241-f2da-438c-8a41-da55431ef301",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1559,"activeRecallAnswers":1561},[1560],"What is the half-life of Carbon-14?",[1562],"5,730 years",{"id":1564,"data":1565,"type":27,"maxContentLevel":35,"version":25,"orbs":1567},"94a910ae-e7b5-4c22-874e-b8c766b62ae3",{"type":27,"title":717,"tagline":1566},"One of the most lethal poisons in the universe.",[1568,1641,1707],{"id":1569,"data":1570,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1572,"introPage":1580,"pages":1586},"46c0367d-4f0e-42b9-b879-ee92d2b8f012",{"type":25,"title":1571},"Introduction and History of Arsenic",{"id":1573,"data":1574,"type":35,"maxContentLevel":35,"version":24},"898e8ae0-3093-42ae-adf4-1fb3651ea06a",{"type":35,"summary":1575},[1576,1577,1578,1579],"Arsenic is a toxic metal found naturally in the Earth's crust","Albertus Magnus isolated arsenic in the 1200s","Ancient Egyptians used arsenic for gilding metals","Dr Fowler's Solution, a Victorian tonic, contained arsenic",{"id":1581,"data":1582,"type":52,"maxContentLevel":35,"version":24},"1cfbed47-7a56-4447-b079-613577f58d33",{"type":52,"intro":1583},[1584,1585],"Where is arsenic located in the periodic table?","Which elements are in the same group as arsenic?",[1587,1611,1628],{"id":1588,"data":1589,"type":24,"maxContentLevel":35,"version":25,"reviews":1592},"0967bd08-1827-45c1-8140-6b66542627b2",{"type":24,"markdownContent":1590,"audioMediaId":1591},"**Arsenic**, a metal, is infamous for its high toxicity. This characteristic has earned it a notorious reputation throughout history, often associated with poison and death. As a naturally occurring element, **arsenic is found in the Earth's crust**. It is present in small amounts in **soil**, **water**, and **air**. It can also be found in higher concentrations in certain minerals.\n\nThe presence of arsenic in the environment is a result of both natural processes, such as volcanic activity and weathering of rocks, and human activities, such as mining and industrial processes.\n\n![Graph](image://4964114a-3813-491c-90dd-a48a578f9812 \"The atomic structure of arsenic. Image: commons:User:Pumbaa (original work by commons:User:Greg Robson), CC BY-SA 2.0 UK \u003Chttps://creativecommons.org/licenses/by-sa/2.0/uk/deed.en>, via Wikimedia Commons\")","8419f9bd-1fc7-4749-a35d-b022987b701c",[1593],{"id":1594,"data":1595,"type":66,"version":24,"maxContentLevel":35},"70a12f2c-e8ee-449b-917c-685dd8925f13",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1596,"multiChoiceQuestion":1600,"multiChoiceCorrect":1602,"multiChoiceIncorrect":1604,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1608,"matchPairsPairs":1609},[1597,1598,1599],"861dc03e-78b9-4cc2-a820-f746ab463e73","a4545f4d-7407-4b89-a1a4-a931977ea5ff","37a0cfa0-08c9-4e5d-8d4c-a1d18b526064",[1601],"Which of the following most closely applies to arsenic?",[1603],"Highly toxic naturally occurring element",[1605,1606,1607],"Constitutes about 21% of Earth's atmosphere","Second lightest element","Used in nuclear weapons",[143],[1610],{"left":717,"right":1603,"direction":35},{"id":1612,"data":1613,"type":24,"maxContentLevel":35,"version":25,"reviews":1616},"4eb1b02d-7e41-443c-ad13-9a8e22521658",{"type":24,"markdownContent":1614,"audioMediaId":1615},"Despite its harmful effects, arsenic is used in various industries due to its unique properties. For instance, arsenic compounds are sometimes used as **rat poisons** and **insecticides**. However, due to its high toxicity, the use of arsenic in these applications is strictly controlled. Regulations are in place to limit the amount of arsenic that can be released into the environment and to protect workers from exposure.\n\nArsenic has been known to humanity since ancient times. It is mentioned on one ancient Egyptian papyrus as a way of gilding metals. This early use of arsenic demonstrates the long-standing recognition of its useful properties, despite its toxicity.","fb254cb5-699a-484c-a581-14b87544fa1a",[1617],{"id":1618,"data":1619,"type":66,"version":24,"maxContentLevel":35},"43a8d4d2-faf1-4d9c-98d2-49ee0de7678b",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1620,"multiChoiceCorrect":1622,"multiChoiceIncorrect":1624,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1621],"What is arsenic known for?",[1623],"Its high toxicity",[1625,1626,1627],"Its use in electroplating","Its radioactive qualities","Its use as a store of value",{"id":1629,"data":1630,"type":24,"maxContentLevel":35,"version":25,"reviews":1633},"1515680a-fb18-4725-a835-6555e6d43196",{"type":24,"markdownContent":1631,"audioMediaId":1632},"The discovery of arsenic is attributed to **Albertus Magnus** in the 1200s. This medieval philosopher and alchemist is said to have been the first to isolate the element. However, the use of arsenic predates this discovery, with evidence of its use dating back to ancient civilizations. Historically, arsenic was often used in **pigments**, **dyes**, and **medicines**.\n\n![Graph](image://0d96cb3a-b462-4e60-bdd6-409283d931ef \"A photo of Albertus Magnus, the medieval philosopher and alchemist who is credited with isolating arsenic. Image: Tommaso da Modena, Public domain, via Wikimedia Commons\")\n\nOne popular cure-all tonic used in Victorian times, **Dr Fowler's Solution**, contained arsenic. This was widely used, and even Charles Dickens is reported to have consumed it. Despite its known toxicity, arsenic was used in these applications due to a lack of understanding of its harmful effects and the absence of safer alternatives.","df21ccdb-1690-4eca-b7f1-635537ecd1fc",[1634],{"id":1635,"data":1636,"type":66,"version":24,"maxContentLevel":35},"3e771110-4fce-4689-a625-7d9c6313d518",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1637,"activeRecallAnswers":1639},[1638],"Who is credited with the discovery of the element arsenic in the 1200s?",[1640],"Albertus Magnus",{"id":1642,"data":1643,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1645,"introPage":1653,"pages":1659},"264f14e5-b27f-4476-8ccc-1bb3a6aca339",{"type":25,"title":1644},"Structure and Properties of Arsenic",{"id":1646,"data":1647,"type":35,"maxContentLevel":35,"version":24},"8b06f3ef-5497-408a-80d4-03f65262e1c6",{"type":35,"summary":1648},[1649,1650,1651,1652],"Arsenic has 33 protons and an atomic mass of 75","Gray arsenic is the most stable and common form at room temperature","Arsenic's toxicity comes from its similarity to phosphorus, disrupting biological reactions","Chronic arsenic exposure can cause skin, lung, and bladder cancer",{"id":1654,"data":1655,"type":52,"maxContentLevel":35,"version":24},"faaa0759-625a-4955-ac71-0363e29d35d5",{"type":52,"intro":1656},[1657,1658],"Why was arsenic used to treat syphilis?","What led to the decline in medical use of arsenic?",[1660,1677,1690],{"id":1661,"data":1662,"type":24,"maxContentLevel":35,"version":25,"reviews":1665},"919b38d1-0904-47f8-8f36-102275e92cdd",{"type":24,"markdownContent":1663,"audioMediaId":1664},"Arsenic is an element with **33 protons** in its atomic structure, giving it an **atomic number of 33**. The only stable isotope of arsenic has 42 neutrons, giving it an atomic mass of 75. Arsenic is a metalloid, meaning that it shares some properties with metals and other properties with non-metals. Arsenic has 3 main allotropes (different forms in the solid state).\n\n![Graph](image://2a51c9b7-0599-41cd-b65f-e28b86d9070e \"Molecular structures of arsenic allotropes. Image: Klodaya, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThese are **gray**, **black** and **yellow**. The different allotropes of arsenic have different physical and chemical properties, which can affect how they interact with other substances and their potential uses.\n\n**Gray arsenic** is the most stable form at room temperature, and also the most common. In this form, also called metallic arsenic, it is bright, silver-grey and brittle but it quickly tarnishes in moist air. **Black arsenic** has very rarely been produced, though it is thought to have some potential as a semiconductor. The **yellow** allotrope of arsenic is the most unstable and the most toxic.","9ec47f8b-f877-4374-8f84-e2901fa6a352",[1666],{"id":1181,"data":1667,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1668,"multiChoiceQuestion":1669,"multiChoiceCorrect":1671,"multiChoiceIncorrect":1672,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1673,"matchPairsPairs":1674},[1178,1182,1183],[1670],"What is the atomic number of arsenic?",[1189],[1187,1190,206],[143],[1675],{"left":1676,"right":1189,"direction":35},"Atomic number of arsenic",{"id":1678,"data":1679,"type":24,"maxContentLevel":35,"version":25,"reviews":1682},"daa52f6d-b080-4c42-9cae-e4d7d7f5fbe5",{"type":24,"markdownContent":1680,"audioMediaId":1681},"Throughout history, arsenic has been used as a poison due to its high toxicity, and the fact that arsenic has no strong smell or taste. This has made it **a popular choice for poisonings** throughout history, as it can be easily added to food or drink without detection. The symptoms of arsenic poisoning can look similar to those of cholera.\n\nArsenic's toxicity relates to its similarity to the element **phosphorous**. Phosphorous is vital to many chemical reactions in biology, and arsenic can substitute for it very easily, disrupting these reactions. This disruption can lead to a variety of health problems, including damage to the nervous system and various types of cancer.","2ed7c108-6155-4911-a484-5d4330939ab3",[1683],{"id":1684,"data":1685,"type":66,"version":24,"maxContentLevel":35},"244ec9a6-7174-40c5-aaf5-be6a7a5c896c",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1686,"activeRecallAnswers":1688},[1687],"Which is the most unstable and toxic allotrope of arsenic?",[1689],"Yellow",{"id":1691,"data":1692,"type":24,"maxContentLevel":35,"version":25,"reviews":1695},"d64f775e-11eb-4e85-bac5-6302d73f51fa",{"type":24,"markdownContent":1693,"audioMediaId":1694},"![Graph](image://1cc18ece-e425-4a6d-b2ff-8e80c93cf515 \"A person exposed to contaminated water showing symptoms of arsenic poisoning. Image: Anita Ghosh/REACH, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nChronic exposure to arsenic can result from contaminated water and can lead to **skin**, **lung**, and **bladder** cancer. This is a significant public health concern in areas where arsenic contamination of water sources is common.\n\nArsenic is part of the **p-block** of the periodic table which includes elements with their outermost electron in a p orbital. This group of elements is known for their diverse range of properties, from nonmetals to metals, and includes some of the most important elements for life, such as **carbon** and **nitrogen**.\n\nArsenic is in **group 15 of the periodic table**, also known as pnictogens. This group includes elements such as nitrogen and phosphorus, which are essential for life. The elements in this group share certain chemical properties, such as the ability to form **three covalent bonds**.\n\nIn addition to arsenic, nitrogen, and phosphorous, group 15 includes antimony, bismuth, and moscovium. Elements in this group vary widely in appearance, and change from non-metals to metals as you descend down the group.","b57e3e2f-72e0-4d12-867a-461f5775de22",[1696],{"id":1182,"data":1697,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1698,"multiChoiceQuestion":1699,"multiChoiceCorrect":1701,"multiChoiceIncorrect":1702,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1703,"matchPairsPairs":1704},[1178,1181,1183],[1700],"What is the group in the periodic table where arsenic is found?",[1190],[1187,1189,206],[143],[1705],{"left":1706,"right":1190,"direction":35},"Group in the periodic table where arsenic is found",{"id":1708,"data":1709,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1711,"introPage":1719,"pages":1725},"e106ad8c-b9e6-435f-8271-5761bed1d093",{"type":25,"title":1710},"Uses and Detection of Arsenic",{"id":1712,"data":1713,"type":35,"maxContentLevel":35,"version":24},"1ee553d5-0dee-4ebe-a084-ef6d358ffa3a",{"type":35,"summary":1714},[1715,1716,1717,1718],"Arsenic was used in pesticides, wood preservatives, and semiconductors","The Marsh test, developed in 1836, detects even tiny amounts of arsenic","Arsenic trioxide treats a specific type of cancer called acute promyelocytic leukemia","Arsenic contamination from human activities can poison wildlife and pollute water",{"id":1720,"data":1721,"type":52,"maxContentLevel":35,"version":24},"c527022a-63f6-4100-ac6e-312c0e8cd16d",{"type":52,"intro":1722},[1723,1724],"Why is oxygen classified as a p-block element?","How does oxygen's electron configuration influence its reactivity compared to other chalcogens?",[1726,1743,1760,1765,1778,1791],{"id":1727,"data":1728,"type":24,"maxContentLevel":35,"version":25,"reviews":1731},"96f1e5f3-7146-4592-9374-71cdff011ca3",{"type":24,"markdownContent":1729,"audioMediaId":1730},"Despite its toxicity, arsenic has been used in a variety of applications. The use of arsenic is regulated by government agencies to protect public health and the environment. These regulations limit the amount of arsenic that can be used in certain products and released into the environment. \n\nArsenic has been used in **pesticides**, **wood preservatives**, and **semiconductors**. Organoarsenic compounds (combining arsenic and carbon) are also sometimes added to poultry feed to improve weight gain. These uses take advantage of the unique properties of arsenic, but also pose potential risks due to arsenic's toxicity.\n\n![Graph](image://ccf4ecd7-ddeb-4b93-baf3-22c964c7ce04 \"Coloured ceramic bowls. Image: Darko Trajković via pexels\")","751d7df5-64c8-421b-bf12-20358d29352d",[1732],{"id":1733,"data":1734,"type":66,"version":24,"maxContentLevel":35},"684701b7-8b90-4139-9ca0-673c83c79779",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1735,"multiChoiceCorrect":1737,"multiChoiceIncorrect":1739,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1736],"What is the purpose of adding organoarsenic compounds to poultry feed?",[1738],"To improve weight gain",[1740,1741,1742],"To prevent illness","To improve hydration","To improve egg production",{"id":1744,"data":1745,"type":24,"maxContentLevel":35,"version":25,"reviews":1748},"1700c2c2-de53-40c2-8ca6-fc9a08d19ca5",{"type":24,"markdownContent":1746,"audioMediaId":1747},"In the past, arsenic was used in the production of **glass** and as a **coloring agent in ceramics**. These uses have largely been phased out due to the health risks associated with arsenic exposure and the development of safer alternatives. \n\n**The Marsh test**, developed by James Marsh and first published in 1836, is a method for detecting arsenic. The Marsh test is highly sensitive and can detect even minute amounts of arsenic. This sensitivity made it a valuable tool in forensic investigations, as it could provide evidence of arsenic poisoning even when only small amounts of the poison were present.\n\n![Graph](image://1ae5457e-02b1-4c40-99f7-09595400baec \"Marsh test apparatus. Image: Hugh McMuigan, Public domain, via Wikimedia Commons\")","0caa2b94-3ef1-4f41-bcae-6e734ce1c874",[1749],{"id":1750,"data":1751,"type":66,"version":24,"maxContentLevel":35},"fcd90d33-ab00-4cc7-8957-50e78aea1228",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1752,"multiChoiceCorrect":1754,"multiChoiceIncorrect":1756,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1753],"What is the Marsh test used for?",[1755],"Detecting arsenic",[1757,1758,1759],"Detecting radium","Detecting gold","Detecting hydrogen",{"id":1761,"data":1762,"type":24,"maxContentLevel":35,"version":25},"455db0ba-a9dd-4d09-8245-c5b13cf5cf77",{"type":24,"markdownContent":1763,"audioMediaId":1764},"The Marsh test played a crucial role in forensic science during the 19th century, helping to solve numerous poisoning cases. Prior to this test, arsenic had been known as **poudre de succession** (inheritance powder) in France, due to its use in poisoning.\n\nThe development of the Marsh test helped to deter this practice by making it easier to detect arsenic poisoning. The test continued to be significant in forensic investigations for more than a century. It was used, with some improvements, in **forensic toxicology** into the 1970s.","10b21fa9-0d02-4d96-973b-dfaf964071a2",{"id":1766,"data":1767,"type":24,"maxContentLevel":35,"version":25,"reviews":1770},"599b9423-f08d-4ba5-9376-321357aedda7",{"type":24,"markdownContent":1768,"audioMediaId":1769},"While arsenic is a highly toxic substance, you might be surprised to learn that it has been used in medicine, notably in the **treatment of syphilis**. This use of arsenic was based on its ability to kill bacteria and other microorganisms.\n\n![Graph](image://c50076f6-85dc-429b-a6f1-33acde14d137 \"An AI illustration of a physician preparing a medicinal concoction with arsenic.\")\n\nBefore the advent of antibiotics, arsenic was a common component in various medicinal treatments. It was used in a variety of forms, from pills to tonics, and was often marketed as a cure-all for a wide range of ailments. However, the harmful effects of arsenic often outweighed any potential benefits, leading to its eventual disuse in most medical applications.","33069051-a971-458e-b110-546335f7a8a7",[1771],{"id":1772,"data":1773,"type":66,"version":24,"maxContentLevel":35},"a3959005-8cd1-469c-a23b-d3472c48d53b",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1774,"activeRecallAnswers":1776},[1775],"What was arsenic historically used for in medicine?",[1777],"Treatment of syphilis",{"id":1779,"data":1780,"type":24,"maxContentLevel":35,"version":25,"reviews":1783},"cd195cbb-ed32-40c5-b55b-e9a9b81e0d9c",{"type":24,"markdownContent":1781,"audioMediaId":1782},"Today, **arsenic trioxide** is used in the treatment of a specific type of cancer called acute promyelocytic leukemia. This use of arsenic is a testament to its potential as a therapeutic agent, despite its toxicity. However, its use in medicine is strictly controlled to minimize the risks associated with arsenic exposure.\n\nArsenic can enter the environment through both natural processes and human activities. Natural processes include volcanic activity and the weathering of rocks, while human activities include **mining**, **smelting**, and the use of arsenic in pesticides and other industrial processes.","3724eaed-9388-4a0c-813e-71be9c7a4a37",[1784],{"id":1785,"data":1786,"type":66,"version":24,"maxContentLevel":35},"dee48f83-a6c0-41d5-a6ed-c5465bfb3102",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":1787,"clozeWords":1789},[1788],"Arsenic can enter the environment through natural processes and human activities.",[1790],"human",{"id":1792,"data":1793,"type":24,"maxContentLevel":35,"version":25},"8815fc29-a99b-4394-a342-7979d08f2b96",{"type":24,"markdownContent":1794,"audioMediaId":1795},"Environmental contamination caused by human activities can have serious impacts on the environment, including the **poisoning of wildlife** and the **pollution of water sources**. Excessive levels of arsenic in soil and water can pose significant health risks to humans and wildlife.\n\nThe risks for humans include a variety of health problems, from **skin and lung cancer** to **cardiovascular disease**. Efforts to reduce arsenic contamination in the environment include improving industrial practices, regulating the use of arsenic, and developing methods for removing arsenic from contaminated water and soil.\n\n![Graph](image://9bf36947-d206-44ef-adcf-8b04af1322d9 \"A volcanic eruption, a natural process that releases arsenic. Image: Suhairy Tri Yadhi, Public Domain via Pexels\")","3808d9c4-fe10-410f-9405-cd51b013abc9",{"id":1797,"data":1798,"type":27,"maxContentLevel":35,"version":25,"orbs":1800},"52f475c3-4b62-44cb-857c-8308e5577072",{"type":27,"title":547,"tagline":1799},"An abundant part of our atmosphere, and an essential part of keeping us alive.",[1801,1872,1941],{"id":1802,"data":1803,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1805,"introPage":1813,"pages":1819},"2a2171dd-86dd-4a71-9bcd-cfa4cfae2bc5",{"type":25,"title":1804},"Introduction to Oxygen",{"id":1806,"data":1807,"type":35,"maxContentLevel":35,"version":24},"21d5573d-06a4-42e6-af89-00dd4f67e41f",{"type":35,"summary":1808},[1809,1810,1811,1812],"Oxygen makes up 21% of Earth's atmosphere and is essential for life","The Great Oxygenation Event was caused by blue-green algae and changed Earth's atmosphere","Oxygen has 8 protons, giving it an atomic number of 8","Oxygen exists in different forms like O2 and O3, each with unique properties",{"id":1814,"data":1815,"type":52,"maxContentLevel":35,"version":24},"87250480-0e7e-4561-bb47-e907386e7034",{"type":52,"intro":1816},[1817,1818],"How does oxygen help cells make energy?","What happens to glucose during aerobic respiration?",[1820,1835,1859],{"id":1821,"data":1822,"type":24,"maxContentLevel":35,"version":25,"reviews":1825},"9fe6aba7-816a-4d90-9646-644e6a0b2b62",{"type":24,"markdownContent":1823,"audioMediaId":1824},"**Oxygen**, a fundamental element for sustaining life on Earth, is a key component of the air we breathe, the water we drink, and the soil in which we grow our food. It is **the third most abundant element in the universe** and makes up around 21% of the Earth's atmosphere. Without oxygen, life as we know it would not exist.\n\n![Graph](image://585bb6d8-1b04-4f03-aee2-d476a17d3204 \"A molecule of oxygen consisting of two oxygen atoms bonded together. Image: Christinelmiller, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nOxygen plays a crucial role in many vital processes that sustain life on our planet. It is essential for the process of **respiration**, where it is used by organisms to convert food into energy. Oxygen is also a key player in the process of **combustion**, where it reacts with a fuel to produce heat and light. This process is used in everything from **heating our homes** to **powering our vehicles**.","fb660cac-0668-4ff3-a975-ea58e9eee944",[1826],{"id":1827,"data":1828,"type":66,"version":24,"maxContentLevel":35},"f39afd89-4772-4bf8-a8a7-c647fc1ea04a",{"type":66,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":1829,"binaryCorrect":1831,"binaryIncorrect":1833},[1830],"What percentage of the earth's atmosphere is made up of oxygen?",[1832],"21%",[1834],"42%",{"id":1836,"data":1837,"type":24,"maxContentLevel":35,"version":25,"reviews":1840},"9c14afbe-c6af-4dc1-b9ff-5ecc60286cf7",{"type":24,"markdownContent":1838,"audioMediaId":1839},"Free oxygen started to appear in Earth's atmosphere between 3 billion and 1 billion years ago, a product of photosynthesis by blue-green algae. This event, known as the Great Oxygenation Event, dramatically changed the Earth's atmosphere and paved the way for the evolution of oxygen-breathing organisms.\n\nOxygen is characterized by having **8 protons in its atomic structure**, which gives it an atomic number of 8. This atomic number determines its place in the periodic table. It also influences the chemical behavior of oxygen, including its reactivity and bonding properties.\n\n![Graph](image://bfc770df-914d-43a7-aa43-f4abdfe24836 \"The electron shell of oxygen. Image: Pumbaa via Wikimedia\")","8c5a3290-147b-47fb-a190-81952faf1d8c",[1841,1852],{"id":1183,"data":1842,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1843,"multiChoiceQuestion":1844,"multiChoiceCorrect":1846,"multiChoiceIncorrect":1847,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1848,"matchPairsPairs":1849},[1178,1181,1182],[1845],"What is the atomic number of oxygen?",[206],[1187,1189,1190],[143],[1850],{"left":1851,"right":206,"direction":35},"Atomic number of oxygen",{"id":1853,"data":1854,"type":66,"version":24,"maxContentLevel":35},"192d5c1a-f0da-400c-b59b-4514f6ee88f8",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":1855,"clozeWords":1857},[1856],"Free oxygen started to appear in Earth's atmosphere between 3 billion and 1 billion years ago, a product of photosynthesis.",[1858],"photosynthesis",{"id":1860,"data":1861,"type":24,"maxContentLevel":35,"version":25,"reviews":1864},"c1c2ce34-92c2-4dbb-9f6d-b883b66cadf1",{"type":24,"markdownContent":1862,"audioMediaId":1863},"The most common isotope of Oxygen also contains **8 neutrons**, giving it an atomic mass of 16. Oxygen exists in several different forms, or allotropes, including **molecular oxygen (O2)** and **ozone (O3)**. These different forms of oxygen have different physical and chemical properties, and many are essential for life on Earth.\n\nOxygen is a **colorless**, **odorless** gas that dissolves readily in water. It is highly reactive, readily forming compounds with most other elements. This reactivity is a key factor in many of the chemical reactions that sustain life on Earth, including respiration and combustion.\n\nLike many of the other elements we've discussed, Oxygen is classified under the **p-block** of the periodic table. This classification is based on the fact that oxygen's outermost electron is in a p orbital. This orbital configuration influences the chemical behavior of oxygen, including its reactivity and bonding properties.\n\nOxygen is in **group 16 of the periodic table**, along with sulfur, selenium, tellurium, and the radioactive elements polonium and livermorium. These elements share similar properties due to their similar electron configurations. They all have six electrons in their outermost energy level, which influences their chemical behavior.\n\nElements in group 16 of the periodic table are known as **chalcogens**. The name chalcogen means '**ore-former**,' reflecting the fact that many ores are compounds of these elements. However, oxygen is often treated separately from the other chalcogens, and sometimes excluded altogether, due to its unique properties and behavior.","34dc9e22-5eb3-49cc-b129-23243ea16aa3",[1865],{"id":1866,"data":1867,"type":66,"version":24,"maxContentLevel":35},"63253ca2-234a-4a43-8d7c-8db76338a067",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1868,"activeRecallAnswers":1870},[1869],"What are the physical properties of Oxygen?",[1871],"Colorless, odorless gas",{"id":1873,"data":1874,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1876,"introPage":1884,"pages":1890},"bf96a998-fcc5-4071-a4da-936d83dd15a0",{"type":25,"title":1875},"History and Theories of Oxygen",{"id":1877,"data":1878,"type":35,"maxContentLevel":35,"version":24},"5edf022e-4d51-469e-82a8-2e8b208bfcad",{"type":35,"summary":1879},[1880,1881,1882,1883],"Phlogiston theory was debunked by the discovery of oxygen","Antoine Lavoisier proved combustion needs oxygen by weighing gases","Joseph Priestley, Carl Scheele, and Antoine Lavoisier discovered oxygen","Oxygen powers cellular respiration, creating energy for cells",{"id":1885,"data":1886,"type":52,"maxContentLevel":35,"version":24},"9def0328-1a0c-4e81-bf3f-bd7bbb7b0927",{"type":52,"intro":1887},[1888,1889],"What role does oxygen play in combustion?","How does cellular respiration use oxygen to produce energy?",[1891,1911,1928],{"id":1892,"data":1893,"type":24,"maxContentLevel":35,"version":25,"reviews":1896},"33525a19-16db-4d4b-b700-2b00c6eec472",{"type":24,"markdownContent":1894,"audioMediaId":1895},"The **phlogiston** theory was a widely accepted explanation for combustion and rusting before the discovery of Oxygen. It held that a fire-like element called phlogiston was found in combustible materials and released during burning. However, the discovery of oxygen provided a more accurate explanation for these processes.\n\nThe role of oxygen in combustion was proved conclusively by the French chemist **Antoine-Laurent Lavoisier**, who demonstrated that combustion requires a gas which has weight by weighing closed vessels. The gas in question was oxygen.\n\n![Graph](image://dc275652-0d16-4149-8fb3-96b53928dc37 \"A portrait of Antoine-Laurent Lavoisier. Image: Jacques-Louis David, Public domain, via Wikimedia Commons\")\n\nThree chemists share credit for the discovery of oxygen: **Joseph Priestley**, **Carl Wilhelm Scheele**, and **Antoine Lavoisier**. From England, Sweden and France respectively, these chemists worked independently of one another. Nevertheless, their work in the late 18th century laid the foundation for our modern understanding of oxygen and its role in chemical reactions.","c5f2fdb9-e4d6-432f-bafc-2b6e7b63e63a",[1897,1904],{"id":1898,"data":1899,"type":66,"version":24,"maxContentLevel":35},"87b09158-6819-4fff-acbb-2becf409b135",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1900,"activeRecallAnswers":1902},[1901],"What theory did the discovery of Oxygen debunk?",[1903],"The phlogiston theory",{"id":1905,"data":1906,"type":66,"version":24,"maxContentLevel":35},"d6aad8fd-8b10-4495-9b77-7eabba8a8bc9",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1907,"activeRecallAnswers":1909},[1908],"Which three scientists are credited for the discovery of oxygen?",[121,1910,119],"Carl Wilhelm Scheele",{"id":1912,"data":1913,"type":24,"maxContentLevel":35,"version":25,"reviews":1916},"52154199-1c10-4395-a4fe-e34202bfb622",{"type":24,"markdownContent":1914,"audioMediaId":1915},"**Combustion** is a chemical reaction in which a substance reacts rapidly with an oxidant, usually atmospheric oxygen, releasing energy in the form of light and heat. This process is fundamental to many aspects of human life, from cooking and heating to transportation and industry.\n\nCombustion requires a **fuel** and an **oxidant**, and produces oxidized, often gaseous products in mixtures known as smoke. The role of oxygen in this process is to act as the oxidant, reacting with the fuel to produce heat and light.\n\nA source of energy (heat) is required to start combustion, but once started the heat from a flame will often produce enough energy to make the reaction self-sustaining. This is why a spark or flame is often used to initiate combustion.","d5cd9442-9d70-43fd-bb72-21cdb603ec86",[1917],{"id":1918,"data":1919,"type":66,"version":24,"maxContentLevel":35},"85ab9602-17e7-45c4-b009-e6290f05ca41",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":1920,"multiChoiceCorrect":1922,"multiChoiceIncorrect":1924,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[1921],"What is the term for a chemical reaction in which a substance reacts rapidly with an oxidant, releasing energy in the form of light and heat?",[1923],"Combustion",[1925,1926,1927],"Oxidation","Titration","Evaporation",{"id":1929,"data":1930,"type":24,"maxContentLevel":35,"version":25,"reviews":1933},"fd407ebf-9de3-484e-a1b6-211e8098dfd7",{"type":24,"markdownContent":1931,"audioMediaId":1932},"Oxygen is used by cells to **generate energy**, a process known as **cellular respiration**. This process involves the breakdown of glucose, a simple sugar, in the presence of oxygen to produce energy in the form of ATP (**adenosine triphosphate**), a molecule that cells use to power their activities. Cellular respiration that takes place in the presence of oxygen is termed aerobic respiration.\n\nThis process is highly efficient and produces a large amount of energy for the cell. **Aerobic cellular respiration** is a vital process for the survival of most organisms, occurring in the cells of plants, animals, fungi, and protists. It is through this process that these organisms are able to convert the energy stored in food into a form that their cells can use.","f39641fc-9ba7-4002-bbb7-468d833638cd",[1934],{"id":1935,"data":1936,"type":66,"version":24,"maxContentLevel":35},"52b1a369-d235-4bbe-a82d-26369ea22127",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1937,"activeRecallAnswers":1939},[1938],"What molecule is produced as a source of energy for cells during aerobic respiration?",[1940],"ATP (adenosine triphosphate)",{"id":1942,"data":1943,"type":25,"version":25,"maxContentLevel":35,"summaryPage":1945,"introPage":1953,"pages":1959},"d634543b-37c5-4cd4-b8f5-74152cd74b74",{"type":25,"title":1944},"Role and Importance of Oxygen",{"id":1946,"data":1947,"type":35,"maxContentLevel":35,"version":24},"62ca6b82-47db-4345-9219-5cc4dbbcf72a",{"type":35,"summary":1948},[1949,1950,1951,1952],"Oxides are compounds formed when oxygen combines with another element, like water (H2O) and rust (Fe2O3)","Most of Earth's crust is made of oxides, which are the building blocks of rocks and soils","Dissolved oxygen in water is crucial for the survival of fish and other aquatic organisms","Oxygen makes up 21% of Earth's atmosphere, essential for aerobic life and maintained by photosynthesis",{"id":1954,"data":1955,"type":52,"maxContentLevel":35,"version":24},"520ed1f4-af47-4d15-9df6-d49a0190c56b",{"type":52,"intro":1956},[1957,1958],"Why is helium chemically stable?","What makes noble gases ideal for lighting?",[1960,1983,1996],{"id":1961,"data":1962,"type":24,"maxContentLevel":35,"version":25,"reviews":1965},"e8b56c43-fed4-41c9-aa20-f2e5f8a28a6c",{"type":24,"markdownContent":1963,"audioMediaId":1964},"**Oxides** are compounds that are formed when oxygen combines with another element. These compounds are incredibly diverse, ranging from **water (H2O)**, where oxygen is combined with hydrogen, to **rust (Fe2O3)**, where oxygen is combined with iron.\n\n![Graph](image://046b7d34-3759-44e8-8c56-e7b6bfa4d5d4 \"Oxide mineral exhibit. Image: Tbennert, CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nThese compounds exhibit a wide range of properties, depending on the element Oxygen combines with. One famous example is **carbon dioxide (CO2)**, a gas that is produced by the combustion of carbon-based fuels and by respiration. Carbon dioxide is also a key player in the Earth's carbon cycle and is a major contributor to global warming.","4dcdd6cc-e41b-48ba-975d-5fabe94bfbc6",[1966,1976],{"id":1597,"data":1967,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":1968,"multiChoiceQuestion":1969,"multiChoiceCorrect":1971,"multiChoiceIncorrect":1972,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":1973,"matchPairsPairs":1974},[1594,1598,1599],[1970],"Which of the following most closely applies to oxygen?",[1605],[1603,1606,1607],[143],[1975],{"left":547,"right":1605,"direction":35},{"id":1977,"data":1978,"type":66,"version":24,"maxContentLevel":35},"2b445ad6-2164-4046-8c1b-18e281322181",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1979,"activeRecallAnswers":1981},[1980],"What term describes compounds formed when oxygen combines with another element?",[1982],"Oxides",{"id":1984,"data":1985,"type":24,"maxContentLevel":35,"version":25,"reviews":1988},"dc6c025b-ca2f-43f6-a054-4e2f04acba59",{"type":24,"markdownContent":1986,"audioMediaId":1987},"Most of Earth's crust is made of oxides. These compounds, which include minerals such as **quartz (SiO2)** and **hematite (Fe2O3)**, are the building blocks of rocks and soils. They play a crucial role in many geological processes, including the formation of rock.\n\nOxygen is a vital component of water, which is crucial for life on Earth. Water is composed of two hydrogen atoms and one oxygen atom **(H2O)**.\n\nWater is used by organisms for everything from **nutrient transport** to **temperature regulation**. Without water, life as we know it would not exist.\n\n![Graph](image://a25f76ce-4c32-4e0c-bd8f-970d2cc91e4b \"Underwater view of coral reef and flock of little fish. Image: Saad Alaiyadhi via Pexels\")","c6dd9b9d-e688-4a26-9dd6-f49c7b77dbeb",[1989],{"id":1990,"data":1991,"type":66,"version":24,"maxContentLevel":35},"7eaf1758-3bd0-4ff7-b0cd-c63e655c21c4",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":1992,"activeRecallAnswers":1994},[1993],"What is the composition of water?",[1995],"Two Hydrogen atoms and one Oxygen atom",{"id":1997,"data":1998,"type":24,"maxContentLevel":35,"version":25,"reviews":2001},"f6ac6634-141a-4d5f-9564-88c8429913ce",{"type":24,"markdownContent":1999,"audioMediaId":2000},"Although oxygen is a component of water, the oxygen molecules in water are bound and **cannot be used by aquatic lifeforms, which instead rely on oxygen dissolved in the water**. This dissolved oxygen is crucial for the survival of fish and other aquatic organisms. It is also important for the health of aquatic ecosystems, as low levels of dissolved oxygen can lead to problems such as algal blooms and fish kills.\n\n![Graph](image://e23eef8e-e508-405e-995d-0a72b149657b \"A molecule of Oxygen. Image: Christinelmiller, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nOxygen constitutes about **21%** of the Earth's atmosphere. This proportion is vital for the survival of aerobic organisms, which require oxygen for respiration.\n\nThe concentration of oxygen in the atmosphere is maintained by the process of **photosynthesis**, in which plants and algae convert carbon dioxide and water into oxygen and glucose.\n\nThis proportion of Oxygen in the atmosphere is vital for the survival of aerobic organisms. If more than 25% of the air was oxygen, many organic compounds would be highly flammable. This would dramatically increase the risk of fires, which could have devastating effects on ecosystems and human societies.\n\nAtmospheric oxygen levels have fluctuated throughout the Earth's history. Oxygen levels probably peaked **around 31% around 300 million years ago**. These fluctuations have been driven by a variety of factors, including changes in volcanic activity, the evolution of life, and the formation and weathering of rocks.","df9c16d5-746a-4c6d-8181-415c41e36c49",[2002,2019],{"id":2003,"data":2004,"type":66,"version":24,"maxContentLevel":35},"e2bb9252-6f02-47c9-bdce-e4b81edfcc7c",{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2005,"multiChoiceQuestion":2009,"multiChoiceCorrect":2011,"multiChoiceIncorrect":2012,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2015,"matchPairsPairs":2016},[2006,2007,2008],"899d4004-58d3-458a-a879-f74f6bdaa4f7","30fdafd9-b52c-4223-9221-c2ab78aee6ce","3e8fd4f1-746d-4801-a53a-a52f926a757c",[2010],"What is the proportion of oxygen in Earth's atmosphere?",[1832],[1529,2013,2014],"75%","99%",[143],[2017],{"left":1832,"right":2018,"direction":35},"Proportion of oxygen in Earth's atmosphere",{"id":2020,"data":2021,"type":66,"version":24,"maxContentLevel":35},"876e3252-5c1a-4870-83e8-d8ac634068b6",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2022,"activeRecallAnswers":2024},[2023],"What percentage of the Earth's atmosphere does Oxygen constitute?",[2025],"About 21%",{"id":2027,"data":2028,"type":27,"maxContentLevel":35,"version":25,"orbs":2030},"1194338b-f106-4e7b-a32a-109790c930a3",{"type":27,"title":545,"tagline":2029},"The second-simplest element in the universe, and a key component of stars.",[2031,2117,2201],{"id":2032,"data":2033,"type":25,"version":25,"maxContentLevel":35,"summaryPage":2035,"introPage":2043,"pages":2049},"7db92cb5-5392-493e-a52d-be2330b9d8b3",{"type":25,"title":2034},"Introduction to Helium",{"id":2036,"data":2037,"type":35,"maxContentLevel":35,"version":24},"04338a59-8097-4a2e-9dd8-89b5c3fffc01",{"type":35,"summary":2038},[2039,2040,2041,2042],"Helium is the second lightest element, right after hydrogen","Helium's full valence shell makes it super stable and unreactive","Helium was discovered by observing a yellow line in the Sun's spectrum","Helium stays liquid down to absolute zero at normal pressure",{"id":2044,"data":2045,"type":52,"maxContentLevel":35,"version":24},"faf494e7-7529-4636-8c63-5dd93b4730bc",{"type":52,"intro":2046},[2047,2048],"How does alpha decay of uranium produce helium-4?","Why does helium escape into space once released into the atmosphere?",[2050,2066,2079,2094,2099,2104],{"id":2051,"data":2052,"type":24,"maxContentLevel":35,"version":25,"reviews":2055},"32e4eb06-a106-4ef4-95f2-725f7230e669",{"type":24,"markdownContent":2053,"audioMediaId":2054},"**Helium**, a noble gas, is distinguished by its low density. It is the second lightest element in the periodic table, surpassed only by hydrogen. This low density is a result of its atomic structure, which consists of **two protons** and, in its most common isotope, **two neutrons**.\n\n![Graph](image://fbe60b2b-114a-44da-8bac-d1da729312fa \"Helium electron shell. Image: Pumbaa, translated by Dbc334, CC BY-SA 2.0 UK \u003Chttps://creativecommons.org/licenses/by-sa/2.0/uk/deed.en>, via Wikimedia Commons\")\n\nOne of the defining characteristics of helium is its **low reactivity**. This is due to its **full valence electron shell**, which makes it chemically stable and resistant to forming compounds with other elements. As a result, helium is **often used in environments where chemical reactions are undesirable**, such as in the cooling of superconducting magnets or as a protective atmosphere in the manufacturing of semiconductors.","af612bbe-d4df-4aae-87db-a61ae779a86b",[2056],{"id":1598,"data":2057,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2058,"multiChoiceQuestion":2059,"multiChoiceCorrect":2061,"multiChoiceIncorrect":2062,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2063,"matchPairsPairs":2064},[1594,1597,1599],[2060],"Which of the following most closely applies to helium?",[1606],[1603,1605,1607],[143],[2065],{"left":545,"right":1606,"direction":35},{"id":2067,"data":2068,"type":24,"maxContentLevel":35,"version":25,"reviews":2071},"5d47c8e2-7481-439e-8eb8-0dfd65e29d32",{"type":24,"markdownContent":2069,"audioMediaId":2070},"In terms of abundance, helium is second only to hydrogen in the universe. This is largely due to the process of **stellar nucleosynthesis**, in which helium is produced through the fusion of hydrogen atoms in stars.\n\nDespite its abundance in the universe, helium is relatively rare on Earth, as it tends to escape from the atmosphere into space due to its low density.\n\nThe first evidence of helium was found by **Pierre Janssen** (also known as Jules Janssen) and **Norman Lockyer**, who independently observed a yellow line in the Sun's spectrum. This discovery was made possible by the use of **spectroscopy**, a technique that allows the identification of elements based on the unique patterns of light they emit or absorb.\n\n![Graph](image://b5f65b24-4c28-435f-88c7-d65b49c12081 \"Pierre Janssen. Image: Atelier Nadar. Photographe, CC0, via Wikimedia Commons\")","7bba5c90-21ac-4f1c-bb35-51d342ff8f29",[2072],{"id":2073,"data":2074,"type":66,"version":24,"maxContentLevel":35},"782cdd5e-5bf7-4c06-b25b-390f15c1d0e4",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2075,"activeRecallAnswers":2077},[2076],"Who first discovered Helium in the Sun's spectrum?",[2078],"Pierre Janssen and Norman Lockyer",{"id":2080,"data":2081,"type":24,"maxContentLevel":35,"version":25,"reviews":2084},"641e42bf-77fd-43e6-a3d3-768d7faed00e",{"type":24,"markdownContent":2082,"audioMediaId":2083},"The first observation of helium was made during a solar eclipse in 1868. This event provided the ideal conditions for Janssen to observe the Sun's spectrum without the interference of the Earth's atmosphere. \n\nIt was during this observation that he noticed a yellow spectral line that could not be attributed to any known element, leading to the discovery of helium. Lockyer subsequently confirmed Janssen’s findings when he viewed the sun’s spectrum through the smog of London.\n\nThe name helium is derived from the Greek word '**Helios**', which means Sun. This name was chosen to reflect the element's place of discovery and its association with solar phenomena. Despite its initial discovery in the Sun, helium is now known to be **present in various locations throughout the universe**, including other stars, natural gas deposits, and the Earth's atmosphere.","e31331c4-a6ab-4c6b-89a8-21c95e49a186",[2085],{"id":2086,"data":2087,"type":66,"version":24,"maxContentLevel":35},"88993664-7717-4087-9582-2e6c8e4a133c",{"type":66,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":2088,"binaryCorrect":2090,"binaryIncorrect":2092},[2089],"Where was helium first observed?",[2091],"In the sun",[2093],"In underground cave systems",{"id":2095,"data":2096,"type":24,"maxContentLevel":35,"version":25},"ad592f40-de94-4fae-a317-c2533c65fc5a",{"type":24,"markdownContent":2097,"audioMediaId":2098},"The atomic structure of helium is characterized by the presence of **two protons**, which gives it an **atomic number of two**.\n\nThe most common isotope of helium, helium-4, has two neutrons in addition to its two protons. This isotope accounts for nearly all of the naturally occurring helium on Earth. \n\nThe presence of two neutrons in the nucleus of a helium-4 atom contributes to its stability, as the neutrons help to offset the repulsive forces between the protons.\n\n![Graph](image://2d765a87-4dd7-43da-b100-402bfcaa98ab \"Atomic structure of helium. Image: BruceBlausde la traducción Ortisa, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")","f4207795-b1db-47da-aebc-2f1bd581b572",{"id":2100,"data":2101,"type":24,"maxContentLevel":35,"version":25},"f87cc5b8-432f-4edf-9669-55367ad2afc3",{"type":24,"markdownContent":2102,"audioMediaId":2103},"One of the most unique properties of helium is that it **cannot be solidified by lowering the temperature at normal pressure**. This is due to the fact that helium remains a liquid down to absolute zero at normal pressure, a property shared by no other element. This behavior is a result of **quantum mechanical effects**, specifically the principle of **zero point energy**.\n\nDespite its placement in the p-block of the periodic table, helium is unique in that its highest energy electrons are in the 1s orbital, not a p orbital. This is due to helium's low atomic number, which means it only has two electrons to fill its orbitals. These electrons both occupy the 1s orbital, which is the lowest energy orbital available.","a848e0ee-b117-4a90-8171-3507e808b851",{"id":2105,"data":2106,"type":24,"maxContentLevel":35,"version":25,"reviews":2109},"198f08b7-428f-46c1-bebf-34be2c62721a",{"type":24,"markdownContent":2107,"audioMediaId":2108},"Helium is found in group 18 of the periodic table, a group collectively termed the noble gases. These elements, which also include neon, argon, krypton, xenon, and radon, are characterized by their full valence electron shells, which make them chemically stable and unreactive.\n\n![Graph](image://9cec0622-fe42-4692-b35b-ca173ea32e6f \"The noble gases from the periodic table.Grasso Luigi, CC BY-SA 4.0 \u003Chttps://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons\")\n\nThe noble gases are **colorless**, **odorless**, **tasteless**, and **nonflammable**. They also have low chemical reactivity, which makes them ideal for use in situations where chemical reactions are undesirable.\n\nDespite their lack of color, **noble gases can emit colorful light** when electrically charged, a property that is utilized in neon lights and other types of lighting.","58d3f66a-679d-4950-afc5-17827c77cb33",[2110],{"id":2111,"data":2112,"type":66,"version":24,"maxContentLevel":35},"9d65bc55-cc0d-45eb-b6a0-9ee23095fbe5",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2113,"activeRecallAnswers":2115},[2114],"What group of the periodic table is characterized by their full valence electron shells, making them chemically stable and unreactive?",[2116],"Noble gases",{"id":2118,"data":2119,"type":25,"version":25,"maxContentLevel":35,"summaryPage":2121,"introPage":2129,"pages":2135},"73f795ca-ab48-426e-b5a9-cf54b29526ba",{"type":25,"title":2120},"Helium in Stars and Radioactive Decay",{"id":2122,"data":2123,"type":35,"maxContentLevel":35,"version":24},"cac51b3b-2431-4952-9000-29422cae0fdc",{"type":35,"summary":2124},[2125,2126,2127,2128],"Helium in stars is made by fusing hydrogen in nuclear reactions","Most helium-4 in the universe was created during the big bang","The Sun is about 25% helium by mass, produced from hydrogen fusion","Earth's helium comes from radioactive decay of uranium and thorium",{"id":2130,"data":2131,"type":52,"maxContentLevel":35,"version":24},"a6a706b0-bed2-43a5-97b1-1c0fec7dfd14",{"type":52,"intro":2132},[2133,2134],"How is helium on Earth mainly produced?","Why is it crucial to manage and conserve helium?",[2136,2149,2177],{"id":2137,"data":2138,"type":24,"maxContentLevel":35,"version":25,"reviews":2141},"c1644f88-b0d0-4724-80eb-a4be1ac931a9",{"type":24,"markdownContent":2139,"audioMediaId":2140},"Helium is formed in stars through the process of **nuclear fusion of hydrogen**. This process involves the combination of hydrogen nuclei to form helium, releasing a large amount of energy in the process. This energy is what powers stars and makes them shine.\n\n![Graph](image://60f3a091-f81a-4e5b-983f-b70f289ec88b \"Cutaway diagram of massive star showing nucleosynthesis in a star. Image: FT2, CC0, via Wikimedia Commons\")\n\nThe process of stellar nucleosynthesis, which involves the fusion of hydrogen atoms to form helium, is a **primary source of helium in the universe**. However, the majority of helium-4 in the universe was actually formed during the big bang, a testament to the element's longevity and stability.","d1a6d0ca-9af1-44ec-8ccc-0e42519f6a08",[2142],{"id":2143,"data":2144,"type":66,"version":24,"maxContentLevel":35},"740ab158-fceb-4d3f-9cbb-119b9676fa1e",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2145,"activeRecallAnswers":2147},[2146],"How is Helium formed in stars?",[2148],"Through the nuclear fusion of Hydrogen",{"id":2150,"data":2151,"type":24,"maxContentLevel":35,"version":25,"reviews":2154},"7dfc2a96-339b-4cd8-9d4c-680461aa8581",{"type":24,"markdownContent":2152,"audioMediaId":2153},"The Sun, like other stars, is composed of approximately **25% helium** by mass. This helium is continually being produced through the fusion of hydrogen in the Sun's core. The remaining 75% of the Sun's mass is primarily **hydrogen**, which serves as the fuel for the ongoing nuclear fusion reactions.\n\n**Alpha decay,** which results in the emission of helium-4 nuclei, is a key process in the production of helium on Earth. Over billions of years, the helium produced by alpha decay has accumulated in the Earth's crust, where it can be extracted from natural gas deposits.","2247ff5c-dc6a-4e18-b9fa-1865db87c7fd",[2155,2166],{"id":2006,"data":2156,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2157,"multiChoiceQuestion":2158,"multiChoiceCorrect":2160,"multiChoiceIncorrect":2161,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2162,"matchPairsPairs":2163},[2003,2007,2008],[2159],"What is the proportion of helium in stars and the Sun?",[1529],[2013,2014,1832],[143],[2164],{"left":1529,"right":2165,"direction":35},"Proportion of helium in stars and the Sun",{"id":2007,"data":2167,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2168,"multiChoiceQuestion":2169,"multiChoiceCorrect":2171,"multiChoiceIncorrect":2172,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2173,"matchPairsPairs":2174},[2003,2006,2008],[2170],"What is the proportion of hydrogen in the Sun?",[2013],[2014,1832,1529],[143],[2175],{"left":2013,"right":2176,"direction":35},"Proportion of hydrogen in the Sun",{"id":2178,"data":2179,"type":24,"maxContentLevel":35,"version":25,"reviews":2182},"04f05826-7ed0-4246-ac4a-bd4bb9d7e94e",{"type":24,"markdownContent":2180,"audioMediaId":2181},"The Earth's crust contains significant amounts of helium that has been built up over billions of years of radioactive decay. Around 99% of the helium produced on Earth comes from the radioactive decay of uranium and thorium in minerals underground. \n\nThis helium is often trapped in natural gas deposits. During natural gas production, these helium deposits are brought to the surface as a by-product. The helium can then be extracted and used.\n\nHowever, once released into the atmosphere, helium can escape into space due to its **low density**.","eb46871a-9053-41fe-baad-e6194b9df087",[2183,2194],{"id":2008,"data":2184,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2185,"multiChoiceQuestion":2186,"multiChoiceCorrect":2188,"multiChoiceIncorrect":2189,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2190,"matchPairsPairs":2191},[2003,2006,2007],[2187],"What is the proportion of Earth's helium produced from radioactive decay?",[2014],[1832,1529,2013],[143],[2192],{"left":2014,"right":2193,"direction":35},"Proportion of Earth's helium produced from radioactive decay.",{"id":2195,"data":2196,"type":66,"version":24,"maxContentLevel":35},"b0d4e16d-7923-4d41-b32b-bdf9bc7ad1ec",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2197,"activeRecallAnswers":2199},[2198],"What process results in the emission of Helium-4 nuclei?",[2200],"Alpha decay",{"id":2202,"data":2203,"type":25,"version":25,"maxContentLevel":35,"summaryPage":2205,"introPage":2213,"pages":2219},"ef364a92-70da-4c9b-8048-d6522aa4407d",{"type":25,"title":2204},"Uses and Applications of Helium",{"id":2206,"data":2207,"type":35,"maxContentLevel":35,"version":24},"3c203e08-8dea-4842-8b98-61ec39a1d48e",{"type":35,"summary":2208},[2209,2210,2211,2212],"Helium cools superconducting magnets in MRI machines and particle accelerators","Helium makes balloons and airships float because it's lighter than air","Helium in deep-sea diving gas prevents nitrogen narcosis","Helium is crucial for the Large Hadron Collider's low temperatures",{"id":2214,"data":2215,"type":52,"maxContentLevel":35,"version":24},"62d60bb1-6f85-4860-a100-cd596187af15",{"type":52,"intro":2216},[2217,2218],"What makes plutonium unique among actinides?","How does plutonium's radioactivity impact its use in nuclear power?",[2220,2233,2238,2251],{"id":2221,"data":2222,"type":24,"maxContentLevel":35,"version":25,"reviews":2225},"21c069c7-5e80-48c7-85ef-ef7e255d71d2",{"type":24,"markdownContent":2223,"audioMediaId":2224},"One of the primary uses of helium is in **cryogenics**, a branch of science dealing with **very low temperatures**, where it serves as a **coolant for superconducting magnets**. These magnets are used in a variety of applications, including magnetic resonance imaging (MRI) machines and particle accelerators. Helium's low boiling point makes it ideal for achieving the extremely low temperatures required for superconductivity.\n\nDue to its low density, helium is often used in lighter-than-air balloons. When a balloon is filled with helium, it becomes lighter than the surrounding air and can float. This property is also utilized in airships and weather balloons.\n\n![Graph](image://aa95c32f-88a1-4bed-b9ff-39786745d950 \"Helium being used to blow up a balloon. Image: Public domain via Pixabay\")","8e7cc671-1fe6-403b-8fab-06010a664565",[2226],{"id":2227,"data":2228,"type":66,"version":24,"maxContentLevel":35},"189754fb-d358-4a7c-a648-2cbc07f08382",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":2229,"clozeWords":2231},[2230],"In cryogenics, helium serves as a coolant for superconducting magnets.",[2232],"superconducting",{"id":2234,"data":2235,"type":24,"maxContentLevel":35,"version":25},"1f1d7dc7-84f4-41f0-89c4-d556d7b19720",{"type":24,"markdownContent":2236,"audioMediaId":2237},"Helium has a number of other uses. In deep-sea diving, helium is used in breathing gas mixtures to reduce the risk of **nitrogen narcosis**, also known as 'the bends', a dangerous condition that can occur when divers breathe compressed air at depth. \n\nIn the semiconductor industry, helium's low reactivity makes it ideal for creating a protective atmosphere during the manufacturing process.","d6c945c5-5f9a-4b6a-864a-6cb041e3f593",{"id":2239,"data":2240,"type":24,"maxContentLevel":35,"version":25,"reviews":2243},"bd0f8912-7a72-41d5-9cce-8f40c5ad0fe3",{"type":24,"markdownContent":2241,"audioMediaId":2242},"The **Large Hadron Collider** is the biggest particle accelerator in the world. It is used to conduct experiments in particle physics, colliding subatomic particles at extreme energy levels, to answer questions about the building blocks of matter and our universe.\n\nThe use of helium in the Large Hadron Collider helps to maintain the **extremely low temperatures** necessary for its operation. Without helium, it would be impossible to achieve the conditions necessary for the superconducting magnets to function, and the collider would not be able to operate.\n\n![Graph](image://c6de24ad-a135-4387-ac0d-af80918525c4 \"The Large Hadron Collider in a tunnel. Image: Maximilien Brice (CERN), CC BY-SA 3.0 \u003Chttps://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons\")\n\nIn 2008, a leak of helium caused a significant delay in the start-up of the Large Hadron Collider. This incident highlighted the importance of helium for the operation of the collider.\n\nThere are growing concerns about a potential shortage of helium due to its increasing use in various industries. Helium has applications in a wide range of industries, including **healthcare**, in the production of **electronic devices** and the **manufacture of fiber optics**, and even in **space exploration**.","d87d83b0-e2c5-40d5-967d-2310ee66d85b",[2244],{"id":2245,"data":2246,"type":66,"version":24,"maxContentLevel":35},"e3c78f1e-49d1-4623-a948-9674968d39d4",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2247,"activeRecallAnswers":2249},[2248],"Why is helium used in the Large Hadron Collider?",[2250],"To maintain extremely low temperatures",{"id":2252,"data":2253,"type":24,"maxContentLevel":35,"version":25,"reviews":2256},"9ce63a60-de8d-46c2-b400-c97d038ea22b",{"type":24,"markdownContent":2254,"audioMediaId":2255},"The rate of helium's replenishment in the atmosphere is slow, as it is primarily produced through **natural radioactive decay**. This slow rate of replenishment, combined with increasing demand, has led to concerns about the long-term availability of helium.\n\nUnlike other gases, helium does not contribute to the greenhouse effect or ozone layer depletion. However, the release of helium into the atmosphere **can contribute to its depletion as a resource**. The supply of helium on Earth is finite, and once released into the atmosphere, it can escape into space and be lost forever. There is growing concern that we are running out of useable helium on earth. Helium is an increasingly scarce resource, which will pose problems in areas such as healthcare, where it is highly valuable.","6d519a3c-e517-47a2-a5f1-2925e2c993ed",[2257],{"id":2258,"data":2259,"type":66,"version":24,"maxContentLevel":35},"ad287c55-c994-4b20-8374-ced87fd4e0bc",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":2260,"multiChoiceCorrect":2262,"multiChoiceIncorrect":2264,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2261],"What is the primary method through which helium is replenished in the atmosphere?",[2263],"Natural radioactive decay",[2265,2266,2267],"Photosynthesis","Emissions from volcanoes","Water vapor rising from the oceans",{"id":2269,"data":2270,"type":27,"maxContentLevel":35,"version":25,"orbs":2273},"a94bc3b8-5194-4e3e-a614-af7f282a8e5c",{"type":27,"title":2271,"tagline":2272},"Plutonium","A radioactive powerhouse - one of the most volatile and unstable elements produced by man.",[2274,2344],{"id":2275,"data":2276,"type":25,"version":25,"maxContentLevel":35,"summaryPage":2278,"introPage":2286,"pages":2292},"f98b3e98-0b50-4a16-a45c-c00f29385a91",{"type":25,"title":2277},"Introduction to Plutonium",{"id":2279,"data":2280,"type":35,"maxContentLevel":35,"version":24},"417b36d9-96b6-4fa9-ac5c-6092efbf5caa",{"type":35,"summary":2281},[2282,2283,2284,2285],"Plutonium is a radioactive metal used in nuclear weapons and reactors","Plutonium-239, with a half-life of 24,400 years, is key in nuclear power","Plutonium is named after the dwarf planet Pluto, following Uranium and Neptunium","Plutonium belongs to the actinides, all of which are radioactive and silver in color",{"id":2287,"data":2288,"type":52,"maxContentLevel":35,"version":24},"b92a4d3d-61ca-4011-9cef-52839ce976db",{"type":52,"intro":2289},[2290,2291],"How is plutonium-239 created?","Why is plutonium crucial for nuclear reactors?",[2293,2309,2324],{"id":2294,"data":2295,"type":24,"maxContentLevel":35,"version":25,"reviews":2298},"c5321dac-388c-4dcf-a609-dd68d3f7777c",{"type":24,"markdownContent":2296,"audioMediaId":2297},"**Plutonium**, a radioactive element, is a key component in the production of nuclear weapons. Its unique properties make it ideal for this purpose, as it can undergo a chain reaction, releasing a large amount of energy in the process. This energy release is what makes nuclear weapons so destructive. The use of plutonium in nuclear weapons has had a profound impact on global politics and warfare, making it a significant element in the modern world.\n\n![Graph](image://bb5fb8a9-991d-4f3a-bb90-99974f826e71 \"Plutonium sample. Image: Maksym Kozlenko via Wikimedia Commons\")\n\nIn addition to its role in nuclear weapons, plutonium is also utilized in **nuclear reactors**. Its ability to undergo fission and release a large amount of energy, make it an effective fuel source for these reactors. Nuclear reactors use this energy to generate electricity, **providing power for millions of homes and businesses** around the world.","c7c6bef5-5109-4161-bef5-c40ad255c146",[2299],{"id":1599,"data":2300,"type":66,"version":24,"maxContentLevel":35},{"type":66,"reviewType":35,"spacingBehaviour":24,"collapsingSiblings":2301,"multiChoiceQuestion":2302,"multiChoiceCorrect":2304,"multiChoiceIncorrect":2305,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6,"matchPairsQuestion":2306,"matchPairsPairs":2307},[1594,1597,1598],[2303],"What element is used in nuclear weapons?",[2271],[717,547,545],[143],[2308],{"left":2271,"right":1607,"direction":35},{"id":2310,"data":2311,"type":24,"maxContentLevel":35,"version":25,"reviews":2314},"26e0aeb2-0aab-4ea1-8866-1092f309c587",{"type":24,"markdownContent":2312,"audioMediaId":2313},"The name plutonium was derived from the dwarf planet Pluto. This naming convention follows the trend set by the preceding elements uranium and neptunium, which were named after the planets Uranus and Neptune respectively.\n\nPlutonium is characterized by its atomic structure, which includes **94 protons**, giving it an **atomic number of 94**. Plutonium’s most stable isotopes are plutonium-244, plutonium-242 and plutonium-239. These contain 150, 148 and 145 neutrons respectively. \n\nPlutonium-239 is produced by the irradiation of uranium during nuclear power production, and has a half-life of 24,400 years. **Around 20 different isotopes of plutonium are known to science**. The existence of different isotopes of Plutonium has significant implications for its use in nuclear technology.\n\n![Graph](image://929a90cb-b208-48fb-8e66-a1fd51beb921 \"Plutonium atomic structure. Image: Pumbaa (original work by Greg Robson), CC BY-SA 2.0 UK \u003Chttps://creativecommons.org/licenses/by-sa/2.0/uk/deed.en>, via Wikimedia Commons\")","858a5cd0-0018-4faf-b7fa-9687a3c046d7",[2315],{"id":2316,"data":2317,"type":66,"version":24,"maxContentLevel":35},"ec8bad68-8d92-4b85-86a6-e42d81d93882",{"type":66,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":2318,"binaryCorrect":2320,"binaryIncorrect":2322},[2319],"How many known isotopes of Plutonium exist?",[2321],"Around 20",[2323],"Around 35",{"id":2325,"data":2326,"type":24,"maxContentLevel":35,"version":25,"reviews":2329},"49dbe8c9-2c06-4b9b-aa61-334047fd0a93",{"type":24,"markdownContent":2327,"audioMediaId":2328},"Plutonium is a **silvery-grey, radioactive metal** that quickly tarnishes when exposed to air. A large piece of plutonium feels warm to the touch because of the energy given off by radioactive decay, and **larger pieces can produce enough heat to boil water**. This property of plutonium is a result of its radioactivity, which causes it to emit energy in the form of heat.\n\nPlutonium is a member of the f block on the periodic table. The f block is a group of elements known as the inner transition metals, which includes the lanthanides and actinides. These elements are characterized by their partially filled f orbitals, which give them unique chemical and physical properties.\n\nPlutonium is part of a group known as the actinides. The actinides are a series of 15 metallic elements, starting from **actinium (Ac)** and ending with **lawrencium (Lr)**. Actinides all look similar to one another, being solid at room temperature and with a silver lustre.\n\n**All actinides are radioactive**, which means they are unstable and decay over time, releasing energy in the process. This radioactivity makes them useful in applications such as nuclear power and medicine, but makes them potentially harmful too.","38ec2156-c9d4-4fd3-9d67-701be659ac88",[2330,2337],{"id":2331,"data":2332,"type":66,"version":24,"maxContentLevel":35},"26b557dc-da59-4425-9e19-c2281f552af8",{"type":66,"reviewType":28,"spacingBehaviour":24,"clozeQuestion":2333,"clozeWords":2335},[2334],"Plutonium is a radioactive metal that can produce enough heat to boil water.",[2336],"boil",{"id":2338,"data":2339,"type":66,"version":24,"maxContentLevel":35},"c413717e-aee9-4dbe-b831-69eb362db5eb",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2340,"activeRecallAnswers":2342},[2341],"What group of elements does the f block include that Plutonium belongs to?",[2343],"Actinides",{"id":2345,"data":2346,"type":25,"version":25,"maxContentLevel":35,"summaryPage":2348,"introPage":2355,"pages":2361},"8aa7b0b0-0240-417c-bbb2-1cfd8976da1d",{"type":25,"title":2347},"History and Uses of Plutonium",{"id":2349,"data":2350,"type":35,"maxContentLevel":35,"version":25},"04b842ee-2e1e-43f4-a41f-c96f920b25fd",{"type":35,"summary":2351},[2352,2353,2354],"Plutonium was first made in 1940 by Glenn T Seaborg's team by bombarding uranium-238 with alpha particles","The 'Fat Man' bomb dropped on Nagasaki in 1945 used plutonium-239, showing its destructive power","Plutonium is a key fuel in nuclear reactors and powers space missions like New Horizons",{"id":2356,"data":2357,"type":52,"maxContentLevel":35,"version":24},"44265e9b-67b6-47f5-b93b-8358ea3384fe",{"type":52,"intro":2358},[2359,2360],"How is plutonium created from uranium?","What role did plutonium play in the development of the atomic bomb?",[2362,2367,2384,2397],{"id":2363,"data":2364,"type":24,"maxContentLevel":35,"version":25},"ca59b36f-565e-4528-9f95-9d9a9348f1c3",{"type":24,"markdownContent":2365,"audioMediaId":2366},"Plutonium was first produced and isolated in 1940 by a team of scientists led by Glenn T. Seaborg. His team, which included Arthur Wahl, Joseph Kennedy, and Edwin McMillan, were able to create Plutonium by bombarding uranium-238 with alpha particles. This produced uranium-238, which decayed to form plutonium.\n\n![Graph](image://0e342964-e05c-47d8-b1d4-f8262fc2c507 \"Glenn T. Seaborg. Image: Atomic Energy Commission, Public Domain via Wikimedia Commons\")\n\nThe discovery of Plutonium was a significant milestone in the field of nuclear science. It opened up new possibilities for the use of nuclear technology, from **power generation** to **weaponry**. The discovery also expanded our understanding of the periodic table and the properties of radioactive elements.\n\nInitially, the amounts of Plutonium produced were so small that they were invisible to the naked eye. However, by 1945, the Americans had produced several kilograms of Plutonium, **enough to make three atomic bombs**. This rapid increase in production demonstrated the potential of nuclear technology and marked a turning point in the history of warfare.","b1ffbd73-1762-46bb-959d-15ab4967ff6a",{"id":2368,"data":2369,"type":24,"maxContentLevel":35,"version":25,"reviews":2372},"2d3cf8b2-b5fd-40dd-839b-daf85afd1d90",{"type":24,"markdownContent":2370,"audioMediaId":2371},"The U.S. government established the Manhattan Project during World War II with the aim of developing an **atomic bomb**. This project brought together some of the brightest minds in science and engineering, and it was during this time that the potential of Plutonium as a fuel for nuclear weapons was fully realized.\n\nPlutonium-239, a specific isotope of Plutonium, was the key ingredient in the 'Fat Man' atomic bomb that was dropped on Nagasaki in 1945. The bomb's destructive power, which resulted in the deaths of **hundreds of thousands of people**, demonstrated the devastating potential of nuclear technology.\n\n![Graph](image://f4192b9e-e53e-4464-ad7d-3bf18109038e \"The Fat Man nuclear bomb. Image: via Wikimedia Commons\")\n\nThe complete detonation of one kilogram of plutonium produces an explosion equivalent to over **10,000 tonnes of chemical explosives**. This immense energy release is a result of the chain reaction that occurs during nuclear fission, where the nucleus of a heavy atom splits into two or more smaller nuclei, releasing a large amount of energy in the process.","88a53710-0d49-4ddd-b1b3-41608c95405d",[2373],{"id":2374,"data":2375,"type":66,"version":24,"maxContentLevel":35},"4f341bd6-649f-489c-b17f-cdf50bf8a4e4",{"type":66,"reviewType":35,"spacingBehaviour":24,"multiChoiceQuestion":2376,"multiChoiceCorrect":2378,"multiChoiceIncorrect":2380,"multiChoiceMultiSelect":6,"multiChoiceRevealAnswerOption":6},[2377],"What was the key ingredient in the 'Fat Man' atomic bomb?",[2379],"Plutonium-239",[2381,2382,2383],"Plutonium-238","Plutonium-237","Plutonium-236",{"id":2385,"data":2386,"type":24,"maxContentLevel":35,"version":25,"reviews":2389},"8b07c582-61bf-48ec-bba0-0820003bb614",{"type":24,"markdownContent":2387,"audioMediaId":2388},"Plutonium is commonly used as **a fuel in nuclear reactors.** Its ability to undergo fission and release a large amount of energy makes it an effective fuel source. This energy is harnessed to generate electricity, providing power for a significant portion of the world's population.\n\n![Graph](image://38f7e7bf-80d8-426f-8235-a7f46ce79424 \"New Horizons spacecraft. Image: Kevin Gill from Los Angeles, CA, United States, CC BY 2.0 \u003Chttps://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons\")\n\nThe greatest source of plutonium is uranium which has undergone irradiation in nuclear reactors. **Plutonium-239**, which can be used to produce nuclear power, is commonly known as Reactor-grade plutonium. This process of transforming uranium into plutonium is a key part of the nuclear fuel cycle.\n\nPlutonium has been used as a source of energy on space missions, such as in the New Horizons spacecraft on its journey to Pluto. The use of plutonium in this context demonstrates its versatility and its importance in the field of space exploration.","000273e1-dbe5-415b-b6a2-0e34abfaa57d",[2390],{"id":2391,"data":2392,"type":66,"version":24,"maxContentLevel":35},"e679906e-47a7-4a28-bdfd-0f505328e9bc",{"type":66,"reviewType":24,"spacingBehaviour":24,"activeRecallQuestion":2393,"activeRecallAnswers":2395},[2394],"What is the term for the plutonium-239 that is used to produce nuclear power and is a key part of the nuclear fuel cycle?",[2396],"Reactor-grade plutonium",{"id":2398,"data":2399,"type":24,"maxContentLevel":35,"version":25,"reviews":2402},"4a66deae-2b21-4199-b498-8e2a4f6c7571",{"type":24,"markdownContent":2400,"audioMediaId":2401},"Plutonium is a synthetic element, meaning **it does not occur naturally** but can be produced in a laboratory. This is achieved through a process known as neutron capture, where a uranium atom absorbs a neutron and transforms through a series of steps into plutonium.\n\nThe creation of synthetic elements like plutonium has expanded the boundaries of the periodic table. These elements, which are not found naturally on Earth, have been created through human ingenuity and technological advancement.\n\nThe ability to produce plutonium in a laboratory setting has been instrumental in its use in nuclear technology. This ability to manipulate and create elements has opened up new possibilities in the field of nuclear science, from power generation to medical applications.\n\nThe potential of plutonium and other synthetic elements is still being explored, and **the possibilities are endless**.","82f339ea-3b09-4ac3-a3ea-c61a9b2910a7",[2403],{"id":2404,"data":2405,"type":66,"version":24,"maxContentLevel":35},"82a049a6-d9d7-491e-9aac-0b2e3344bcc9",{"type":66,"reviewType":25,"spacingBehaviour":24,"binaryQuestion":2406,"binaryCorrect":2408,"binaryIncorrect":2410},[2407],"What kind of element is plutonium?",[2409],"Synthetic",[2411],"Naturally-occurring",{"left":4,"top":4,"width":2413,"height":2413,"rotate":4,"vFlip":6,"hFlip":6,"body":2414},24,"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m9 18l6-6l-6-6\"/>",{"left":4,"top":4,"width":2413,"height":2413,"rotate":4,"vFlip":6,"hFlip":6,"body":2416},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M12.586 2.586A2 2 0 0 0 11.172 2H4a2 2 0 0 0-2 2v7.172a2 2 0 0 0 .586 1.414l8.704 8.704a2.426 2.426 0 0 0 3.42 0l6.58-6.58a2.426 2.426 0 0 0 0-3.42z\"/>\u003Ccircle cx=\"7.5\" cy=\"7.5\" r=\".5\" fill=\"currentColor\"/>\u003C/g>",1778179493200]