A-LevelChemistryChemical periodicity9701/12 · Oct/Nov 2016 · Q121 Mark

The graph below shows the variation of the first ionisation energy with proton number for some elements. The letters used are not the usual symbols for the elements. [Figure showing first ionisation energy vs proton number graph with points P, Q, R, S, T, U, V, W, X] Which statement about the elements is correct?

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AP and X are in the same period in the Periodic Table.

BThe general increase from Q to X is due to increasing atomic radius.

CThe small decrease from R to S is due to decreased shielding.

DThe small decrease from U to V is due to repulsion between paired electrons.

✓ Correct answer

D: The small decrease from U to V is due to repulsion between paired electrons.

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Topic: Chemical periodicity, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, Oct/Nov 2016 Paper 1 Variant 2, question 12.

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