Group 2 metals include magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba). These metals react with water and with oxygen. Using your knowledge of the reactivity series and the properties of Group 2 metals, explain how the reactions of Group 2 metals with water change as you move down the group, and describe what is observed when magnesium is burned in oxygen.

Edexcel A-Level Chemistry (9CH0) — 4.1 Group 2 metals · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Group 2 metals are found in the second column of the periodic table. They all form 2+ cations when they react.

Model answer (5 marks)

1. Reactivity of Group 2 metals increases down the group.
2. Consequently, Ca, Sr and Ba react more vigorously and faster with water than Mg.
3. The reaction proceeds by loss of two electrons to give M²⁺ cations.
4. Burning Mg in oxygen gives a white solid, MgO.
5. This is an oxidation reaction – Mg loses electrons and O gains them.

Examiner tips

  • Use the command word ‘explain’ – give cause and effect. Mention the trend in reactivity down the group. State the product and its colour. Show that Mg is oxidised (loses electrons).

Common mistakes

  • Confusing the colour of magnesium oxide with a different compound. Forgetting that Mg is oxidised (not reduced). Saying the reaction is ‘reduction’ instead of ‘oxidation’.

Mark scheme (5 marks)

  1. Reactivity increases as you go down Group 2
  2. Metals lower in Group 2 react more vigorously / faster with water
  3. Magnesium (and other Group 2 metals) lose electrons to form 2+ cations when reacting
  4. When magnesium is burned in oxygen, a white solid (magnesium oxide) is produced
  5. The burning of magnesium in oxygen is an oxidation reaction because magnesium gains oxygen

Key terms in this question

reactivity series

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