# Describe the trend in boiling points of the halogens as you go down Group 7, and explain why this trend occurs.

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

> The halogens in Group 7 include fluorine, chlorine, bromine, iodine, and astatine. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.

## Mark scheme (5 marks)

1. Boiling points increase going down Group 7
2. The molecules / atoms get larger / have more electrons going down the group
3. Stronger intermolecular forces (London dispersion forces / van der Waals forces) between the molecules
4. More energy is needed to overcome these stronger intermolecular forces
5. Therefore the boiling point is higher for halogens lower in the group (e.g. iodine has a higher boiling point than chlorine)

## Key terms

- [boiling point](https://www.gradenine.co.uk/glossary/boiling-point)
- [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 "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/describe-the-trend-in-boiling-points-ed45d340) · Published by Druglandscape Ltd.