# Strontium and magnesium are both Group 2 elements. When each metal is heated in oxygen, it forms a metal oxide. Explain why strontium oxide dissolves in water to form an alkaline solution, and why strontium reacts more vigorously with oxygen than magnesium does.

> AQA A-Level Chemistry (7405) — 3.2.2 Group 2, the alkaline earth metals · Explain · 5 marks

## Mark scheme (5 marks)

1. Strontium oxide is a basic oxide (accept: metal oxide is basic/alkaline)
2. Strontium oxide reacts with water to form strontium hydroxide
3. Strontium hydroxide dissociates / ionises in water, releasing OH⁻ ions (which makes the solution alkaline)
4. Strontium has more electron shells / its outer electrons are further from the nucleus than magnesium
5. So the outer electrons in strontium are lost more easily / strontium loses electrons more readily, making it more reactive

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/strontium-and-magnesium-are-both-group-ca18fa02) · Published by Druglandscape Ltd.