# Calcium chloride is an ionic compound formed when calcium reacts with chlorine. Explain how calcium chloride is formed from its elements, including how the ions are formed and why the compound has the formula CaCl₂.

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

> Calcium is in Group 2 of the periodic table. Chlorine is in Group 7 of the periodic table.

## Mark scheme (5 marks)

1. Calcium atom loses 2 electrons to form a Ca²⁺ ion
2. Each chlorine atom gains 1 electron to form a Cl⁻ ion
3. Electrons are transferred from calcium to chlorine (not shared)
4. Both ions achieve a full outer shell / stable electronic configuration
5. Two chloride ions are needed to accept the two electrons from one calcium atom, so the formula is CaCl₂

## Key terms

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

## 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/calcium-chloride-is-an-ionic-compound-6fa192dd) · Published by Druglandscape Ltd.