# Chlorine, bromine and iodine are halogens in Group 7. A student investigates the physical properties and bonding of these elements. Describe how the physical properties of the halogens change going down Group 7 from chlorine to iodine, and explain why these changes occur in terms of atomic structure and intermolecular forces.

> Edexcel A-Level Chemistry (9CH0) — 4.2 Group 7 halogens · Describe · 5 marks

> Chlorine is a pale yellow-green gas at room temperature. Bromine is a dark orange-brown liquid at room temperature. Iodine is a shiny grey-black solid at room temperature.

## Mark scheme (5 marks)

1. The boiling point (or melting point) increases going down Group 7 from chlorine to iodine
2. The atoms become larger / have more electron shells going down Group 7
3. Larger atoms / molecules have stronger London dispersion forces (van der Waals forces / intermolecular forces) between molecules
4. More energy is needed to overcome the stronger intermolecular forces, so the boiling point is higher
5. The colour of the halogens becomes darker / deeper going down Group 7 (chlorine is pale yellow-green, bromine is orange-brown, iodine is grey-black)

## Key terms

- [halogens](https://www.gradenine.co.uk/glossary/halogens)
- [Group 7](https://www.gradenine.co.uk/glossary/group-7)
- [intermolecular forces](https://www.gradenine.co.uk/glossary/intermolecular-forces)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/chlorine-bromine-and-iodine-are-halogens-8bcc0439) · Published by Druglandscape Ltd.