# Sodium and potassium are both alkali metals in Group 1 of the periodic table. When a small piece of potassium is added to water, it reacts more vigorously than sodium does with water. Explain why potassium reacts more vigorously with water than sodium does, and describe two observations a student would make when potassium is added to water.

> Edexcel A-Level Chemistry (9CH0) — Topic 2 Inorganic chemistry and the Periodic Table · Explain · 5 marks

> Alkali metals react with cold water to produce a metal hydroxide and hydrogen gas. Potassium is below sodium in Group 1.

## Mark scheme (5 marks)

1. Potassium atoms have more electron shells (energy levels) than sodium atoms
2. The outer electron in potassium is further from the nucleus / more shielded from the nucleus
3. The outer electron is lost more easily in potassium, so it reacts more vigorously
4. One correct observation: the potassium moves around / fizzes / melts into a ball on the surface of the water
5. Second correct observation: potassium burns with a lilac / purple flame OR the potassium ignites

## Key terms

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

## 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/sodium-and-potassium-are-both-alkali-7a547da8) · Published by Druglandscape Ltd.