# Sodium is a metal that is soft and has a relatively low melting point, whilst tungsten is a metal used in light bulb filaments because it has a very high melting point. Using your knowledge of metallic bonding, explain why tungsten has a much higher melting point than sodium.

> Edexcel A-Level Chemistry (9CH0) — 2.3 Metallic bonding · Explain · 5 marks

> Sodium has one electron in its outer shell and forms a 1+ ion. Tungsten has six electrons in its outer shell and forms ions with a higher charge. Both metals consist of a lattice of positive metal ions surrounded by a sea of delocalised electrons.

## Mark scheme (5 marks)

1. Both metals contain a giant lattice of positive metal ions surrounded by / attracted to a sea of delocalised electrons
2. Tungsten ions have a higher charge / more electrons are delocalised per atom than in sodium
3. The electrostatic attraction between the positive ions and the delocalised electrons is stronger in tungsten than in sodium
4. More energy is needed to overcome / break these stronger attractions in tungsten
5. Therefore tungsten has a higher melting point than sodium (linked conclusion)

## Key terms

- [metallic bonding](https://www.gradenine.co.uk/glossary/metallic-bonding)
- [melting point](https://www.gradenine.co.uk/glossary/melting-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/sodium-is-a-metal-that-is-e66f6385) · Published by Druglandscape Ltd.