# Barium is an alkaline earth metal in Group 2. When barium reacts with water, a metal hydroxide and a gas are produced. Explain why barium reacts more vigorously with water than magnesium does, and state the name of the gas produced in this reaction.

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

> Alkaline earth metals react with water to form metal hydroxides and hydrogen gas. The reactivity of Group 2 elements increases down the group.

## Mark scheme (5 marks)

1. Barium atoms are larger than magnesium atoms / barium has more electron shells than magnesium
2. The outer electrons in barium are further from the nucleus than in magnesium
3. There is greater shielding of the outer electrons from the nuclear charge in barium than in magnesium
4. The outer electrons are lost more easily in barium / the attraction between the nucleus and outer electrons is weaker in barium
5. The gas produced is hydrogen

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