Case study·Standard multi-step (3/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A museum display compares three stages in periodic classificatio; Mendeleev arranged elements by atomic mass but left gaps; Moseley's work led to ordering by atomic number.
Total: 5 marks
(a) Which stage explains the modern basis of the periodic table? (1 mark)
(b) Why were Mendeleev's gaps not merely empty spaces? (2 marks)
(c) Why was Newlands' octave pattern not sufficient as a final classification? (2 marks)
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