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?
✓ Correct Answer
The correct answer is D: The small decrease from U to V is due to repulsion between paired electrons.
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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