# Neon (Ne) is a simple molecular substance that exists as individual atoms. It is a gas at room temperature with a boiling point of –246 °C. Krypton (Kr) is also a simple molecular substance that exists as individual atoms. It has a boiling point of –153 °C. Explain why both neon and krypton have very low boiling points, and why krypton has a higher boiling point than neon.

> Edexcel A-Level Chemistry (9CH0) — 2.4 Forces between molecules · Explain · 5 marks

> Neon has a relative atomic mass of 20. Krypton has a relative atomic mass of 84. Both are noble gases that exist as simple molecules.

## Mark scheme (5 marks)

1. Both neon and krypton have low boiling points because the forces between molecules (intermolecular forces) are weak
2. Only a small amount of energy is needed to overcome these weak intermolecular forces
3. Krypton has a higher boiling point than neon because krypton has more electrons / a greater relative atomic mass
4. More electrons means stronger intermolecular forces in krypton
5. More energy is needed to overcome the stronger intermolecular forces in krypton, so it has a higher boiling point

## Key terms

- [simple molecular substance](https://www.gradenine.co.uk/glossary/simple-molecular-substance)
- [boiling point](https://www.gradenine.co.uk/glossary/boiling-point)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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/neon-ne-is-a-simple-molecular-664bccb0) · Published by Druglandscape Ltd.