# Chlorine, bromine and iodine are all halogens in Group 7 of the periodic table. Describe and explain the trend in reactivity of the halogens as you go down Group 7, and explain what happens when chlorine water is added to a solution of potassium bromide.

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

## Mark scheme (4 marks)

1. Reactivity decreases going down Group 7
2. Each halogen atom gains one electron to form a halide ion, and atoms become larger down the group so gaining an electron becomes more difficult / less easy
3. Chlorine displaces bromide ions from potassium bromide solution / a displacement reaction occurs
4. The solution turns orange/brown (as bromine is produced)

## Key terms

- [halogens](https://www.gradenine.co.uk/glossary/halogens)
- [reactivity](https://www.gradenine.co.uk/glossary/reactivity)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/chlorine-bromine-and-iodine-are-all-0c0601ab) · Published by Druglandscape Ltd.