formulaUrl":null,"initialIndex":11,"initialQuestionWindow":[{"id":"0fede7fd-d39f-4400-a5e5-a0b4cc1ec717","revisionId":"b94e6bb8-7045-4069-af93-08833307a455","questionNumber":null,"questionType":"LA","specification":"Dmitri Mendeleev published his periodic table in 1871, long before the discovery of subatomic particles. The modern periodic table is built upon our current understanding of atomic structure.","difficulty":6,"difficultyBand":"hard","totalMarks":5,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"d73e1a9d-1afb-4ffc-850b-f790e45e47d1","label":null,"content":"Describe three key differences between Mendeleev's periodic table and the modern periodic table, explaining how these differences relate to modern concepts of atomic structure (such as protons, neutrons, isotopes, or electrons).","markscheme":"- Mendeleev ordered elements by **relative atomic mass**, whereas the modern table orders them by **atomic number** (proton number) B1\n- Mendeleev left **gaps** for undiscovered elements, whereas the modern table has **no gaps** because elements are known for every consecutive atomic number up to 118 B1\n- Mendeleev had to manually reverse the order of some elements (e.g. Tellurium and Iodine) to match chemical properties, whereas the modern table naturally resolves this because ordering by proton number accounts for mass anomalies caused by **isotopes** (differing neutron numbers) B1\n- Mendeleev's table **lacked Group 0 / Noble Gases**, whereas the modern table includes them due to their stable, **full outer electron shells** B1\n- Mendeleev's table had no separate **transition metal block**, whereas the modern table is organized into blocks (s, p, d, f) based on **electron subshells** B1","marks":5,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"atomic_structure_comparison","label":"Compare the two tables","steps":[{"type":"text","order":0,"title":"Plan three comparisons","content":"Choose **any three** clear differences. For each one, state what Mendeleev did, state the modern equivalent, then link it directly to atomic structure. That structure gives three distinct marking points without needing a long introduction.","highlights":[{"text":"Describe three key differences","location":"specification"},{"text":"explaining how these differences relate to modern concepts of atomic structure","location":"specification"}]},{"type":"text","order":1,"title":"Compare the ordering","content":"Mendeleev arranged elements by **relative atomic mass**. The modern table arranges them by **atomic number**, which is the number of protons in the nucleus.\n\nThis is one complete comparison linked to atomic structure, so it earns a marking point.","highlights":[{"text":"Mendeleev's periodic table","location":"specification"},{"text":"modern periodic table","location":"specification"},{"text":"protons, neutrons, isotopes, or electrons","location":"specification"}]},{"type":"text","order":2,"title":"Explain reversed elements","content":"When ordering by mass, Mendeleev sometimes had to reverse elements, such as tellurium and iodine, so that elements with similar properties stayed together.\n\nThe modern table does not need this adjustment because it uses proton number. An element can have isotopes: atoms with the same number of protons but different numbers of neutrons. These can change its relative atomic mass without changing its position in the modern table. This earns a second marking point.","highlights":[{"text":"Mendeleev's periodic table","location":"specification"},{"text":"modern periodic table","location":"specification"},{"text":"protons, neutrons, isotopes, or electrons","location":"specification"}]},{"type":"text","order":3,"title":"Compare noble gases","content":"Mendeleev's table did not include Group 0, the noble gases, because they had not yet been discovered. The modern table includes them.\n\nNoble gases have full outer electron shells. This makes them very unreactive, explaining why they form their own group. This is a

Atomic structure

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Atomic structure Questions

Atomic structure

Question 2

Atomic structure Questions