# Astatine is a halogen found below iodine in Group 7. A student states: 'Astatine must be a better oxidising agent than iodine and will displace iodine from a solution of potassium iodide.' Evaluate the student's statement.

> AQA A-Level Chemistry (7405) — 3.2.3 Group 7(17), the halogens · Evaluate · 5 marks

## Mark scheme (5 marks)

1. Astatine is a worse (less powerful) oxidising agent than iodine, not a better one
2. Oxidising ability / reactivity decreases going down Group 7
3. Because the outer shell / outermost electrons are further from the nucleus in astatine than in iodine
4. So astatine attracts / gains an electron less easily than iodine (increased shielding / less effective nuclear attraction)
5. Therefore astatine would NOT displace iodine from potassium iodide solution — the student's conclusion is incorrect

## Key terms

- [oxidising agent](https://www.gradenine.co.uk/glossary/oxidising-agent)
- [Group 7](https://www.gradenine.co.uk/glossary/group-7)

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
- [How to answer "Evaluate" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/astatine-is-a-halogen-found-below-1674757d) · Published by Druglandscape Ltd.