# Sodium chloride is an ionic compound formed when sodium reacts with chlorine. Explain how a sodium atom and a chlorine atom each form ions, and state why the charges in sodium chloride balance to give an overall neutral compound.

> WJEC A-Level Chemistry (Wales) — 3.5 Aromatic chemistry (A-Level only) · Explain · 5 marks

> Sodium is in Group 1 of the periodic table. Chlorine is in Group 7 of the periodic table.

## Mark scheme (5 marks)

1. Sodium loses one electron to form a Na⁺ ion
2. Sodium forms a positive ion because electrons have a negative charge / losing an electron leaves a positive charge
3. Chlorine gains one electron to form a Cl⁻ ion
4. Atoms form ions to achieve a full outer shell of 8 electrons / stable electron arrangement
5. The +1 charge on Na⁺ and the −1 charge on Cl⁻ cancel / balance, giving an overall neutral compound with a 1:1 ratio of 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 WJEC A-Level Chemistry (Wales)](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-chloride-is-an-ionic-compound-da0c2f1e) · Published by Druglandscape Ltd.