# Magnesium oxide is an ionic compound formed when magnesium burns in oxygen. Explain how magnesium oxide is formed, including how the ions are produced and why the compound is held together.

> OCR A-Level Chemistry B: Salters (H433) — 2.1 Atoms, compounds, molecules and equations · Explain · 5 marks

> Magnesium is a metal in Group 2 of the periodic table. Oxygen is a non-metal in Group 6. When magnesium burns in oxygen, a white solid, magnesium oxide, is formed.

## Mark scheme (5 marks)

1. Magnesium loses two electrons (to form a 2+ ion / Mg²⁺)
2. Oxygen gains two electrons (to form a 2− ion / O²⁻)
3. Both ions are formed / a metal atom loses electrons and a non-metal gains those electrons
4. An ionic bond is formed between the oppositely charged ions (Mg²⁺ and O²⁻)
5. The compound is held together by strong electrostatic forces (of attraction between the oppositely charged ions)

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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-869c0931) · Published by Druglandscape Ltd.