DP Chemistry (last assessment 2024)

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Question 20N.2.sl.TZ0.a(iii)

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Date November 2020 Marks available [Maximum mark: 2] Reference code 20N.2.sl.TZ0.a(iii)
Level sl Paper 2 Time zone TZ0
Command term Outline Question number a(iii) Adapted from N/A
a(iii).
[Maximum mark: 2]
20N.2.sl.TZ0.a(iii)

Chlorine undergoes many reactions.

Outline why the chlorine atom has a smaller atomic radius than the sulfur atom.

[2]

Markscheme

Cl has a greater nuclear charge/number of protons/Zeff «causing a stronger pull on the outer electrons» ✔

same number of shells
OR
same «outer» energy level
OR
similar shielding ✔

Examiners report

Only about a third of the candidates identified the extra proton in the chlorine nucleus as the cause of the smaller atomic radius when compared to the sulfur atom, and only the stronger candidates also compared the shielding or the number of shells in the two atoms. Many candidates had a poor understanding of factors affecting atomic radius and could not explain the difference.

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