# Caesium (Cs) is an alkali metal in Group 1 of the periodic table, below potassium. State and explain two properties of caesium that you would expect based on its position in Group 1, compared to the alkali metals above it.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 2.1 Group 1 (alkali metals) · State and explain · 4 marks

> Caesium is a soft, silvery-white alkali metal. It is element 55 and sits near the bottom of Group 1 of the periodic table.

## Mark scheme (4 marks)

1. Caesium has a lower melting point than the alkali metals above it (e.g. lower than sodium or potassium)
2. Melting point decreases down Group 1 because the metallic bonds become weaker as atomic/ionic radius increases
3. Caesium is more reactive than the alkali metals above it (e.g. more reactive than potassium/sodium/lithium)
4. Reactivity increases down Group 1 because the outer electron is further from the nucleus / lost more easily, so caesium loses its outer electron more readily

## Key terms

- [alkali metals](https://www.gradenine.co.uk/glossary/alkali-metals)
- [Group 1](https://www.gradenine.co.uk/glossary/group-1)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "State and explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/caesium-cs-is-an-alkali-metal-e2093c9a) · Published by Druglandscape Ltd.