# Lithium fluoride is an ionic compound formed when lithium reacts with fluorine. Explain how lithium fluoride is formed from its elements, and why it has a high melting point.

> Edexcel A-Level Chemistry (9CH0) — 2.1 Ionic bonding · Explain · 5 marks

> Lithium is in Group 1 of the periodic table. Fluorine is in Group 7 of the periodic table. Lithium fluoride is used in specialist optical equipment because it can withstand very high temperatures.

## Mark scheme (5 marks)

1. Lithium loses one electron (to form a Li⁺ ion with a full outer shell / stable electronic configuration)
2. Fluorine gains one electron (to form an F⁻ ion with a full outer shell / stable electronic configuration)
3. The oppositely charged ions attract each other / there is electrostatic attraction between Li⁺ and F⁻ ions
4. Lithium fluoride has a giant ionic lattice structure with many strong electrostatic attractions throughout the lattice
5. A large amount of energy is needed to overcome / break all of these strong electrostatic attractions, so the melting point is high

## Key terms

- [ion](https://www.gradenine.co.uk/glossary/ion)
- [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/lithium-fluoride-is-an-ionic-compound-f05ebed6) · Published by Druglandscape Ltd.