A-LevelChemistryChemical periodicity9701/12 · Feb/Mar 2022 · Q11 Mark

The first ionisation energy of potassium, K, is 418 kJ mol⁻¹. The first ionisation energy of strontium, Sr, is 548 kJ mol⁻¹. Which statement helps to explain why Sr has a greater first ionisation energy than K?

AThe charge on a Sr nucleus is greater than the charge on a K nucleus.

BThe outer electron in a Sr atom experiences greater shielding than the outer electron in a K atom.

CThe outer electron in a Sr atom experiences spin-pair repulsion.

DThe outer electron in a Sr atom is further from the nucleus than the outer electron in a K atom.

✓ Correct answer

A: The charge on a Sr nucleus is greater than the charge on a K nucleus.

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Topic: Chemical periodicity, A-Level Chemistry (syllabus 9701). Multiple choice, 1 mark.
Source: A-Level Chemistry, Feb/Mar 2022 Paper 1 Variant 2, question 1.

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