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Chlorine versus bromine reactivity
Halogens are elements in Group 7 of the periodic table.
Explain why chlorine is more reactive than bromine.
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Marking points
- 1 Compares chlorine as having fewer shells or a smaller atomic radius.
- 2 Links this to the outer shell being closer to the nucleus or to reduced shielding.
- 3 States that the attraction for an incoming electron is stronger.
- 4 Concludes that chlorine gains an electron more easily.
Full-mark answer
Chlorine has fewer electron shells than bromine, so its outer shell is closer to the nucleus and there is less shielding. The nucleus therefore attracts an incoming electron more strongly, so chlorine gains an electron more easily and is more reactive.
Why this answer loses marks
Chlorine is more reactive because it has fewer electrons.
Total electron number is not the scoring link; connect fewer shells and less shielding to stronger attraction and easier electron gain.