# Magnesium oxide is an ionic compound with a giant lattice structure. Explain why magnesium oxide has a high melting point and does not conduct electricity when solid, but does conduct electricity when molten.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.6 Ionic compounds · Explain · 4 marks

## Mark scheme (4 marks)

1. Magnesium oxide consists of oppositely charged ions held together by strong electrostatic forces
2. A large amount of energy is needed to overcome these strong electrostatic forces, so the melting point is high
3. In the solid state the ions are fixed in position in the lattice and cannot move, so it cannot conduct electricity
4. When molten, the ions are free to move and can carry charge / conduct electricity

## Key terms

- [ionic compound](https://www.gradenine.co.uk/glossary/ionic-compound)
- [lattice](https://www.gradenine.co.uk/glossary/lattice)
- [ion](https://www.gradenine.co.uk/glossary/ion)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/magnesium-oxide-is-an-ionic-compound-0f589620) · Published by Druglandscape Ltd.