# Fluorine, chlorine, bromine and iodine are all halogens in Group 7. A student claims that chlorine is a more powerful oxidising agent than iodine, and uses a displacement reaction to support this claim. Explain what is meant by the term 'oxidising agent' and explain, in terms of electron transfer, why chlorine is able to displace iodine from a solution of potassium iodide.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 2.2 Group 7 (halogens) · Explain · 4 marks

## Mark scheme (4 marks)

1. An oxidising agent gains electrons (and is itself reduced)
2. Chlorine is more reactive than iodine (higher oxidising power / higher reactivity down Group 7 decreases)
3. Each chlorine atom gains one electron (from the iodide ions) to form chloride ions (Cl⁻)
4. Iodide ions lose electrons and are oxidised to form iodine molecules (I₂)

## Key terms

- [oxidising agent](https://www.gradenine.co.uk/glossary/oxidising-agent)
- [displacement](https://www.gradenine.co.uk/glossary/displacement)
- [halogens](https://www.gradenine.co.uk/glossary/halogens)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" 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/fluorine-chlorine-bromine-and-iodine-are-4a1900b5) · Published by Druglandscape Ltd.