Magnesium and calcium are both elements in Group 2 of the periodic table. Explain why magnesium and calcium have similar chemical properties, and why calcium is more reactive than magnesium.

Eduqas A-Level Chemistry — 2.2 Group 1, 2 and 7 · Explain · 5 marks · View as Markdown

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

Model answer (5 marks)

Elements in the same group have the same number of electrons in their outer shell.
The number of outer‑shell electrons determines chemical properties, so similar outer‑shell electrons means similar chemical properties.
Calcium has more electron shells than magnesium.
The outer electron in calcium is less strongly attracted to / held by the nucleus.
Therefore calcium loses its outer electrons more easily, making it more reactive.

Examiner tips

  • Use the command word ‘Explain’ – give reasons and link them to the points in the mark scheme.
  • Show the group‑property reasoning first, then the reactivity difference.
  • Use correct UK spelling (e.g. ‘reactive’).

Common mistakes

  • Confusing the number of valence electrons with the total number of electrons.
  • Failing to mention that calcium has an extra electron shell.
  • Using vague phrases like ‘more reactive’ without explaining why.

Mark scheme (5 marks)

  1. Elements in the same group have the same number of electrons in their outer shell
  2. The number of outer shell electrons determines chemical properties, so similar outer shell electrons means similar chemical properties
  3. Calcium has more electron shells than magnesium
  4. The outer electron in calcium is less strongly attracted to / held by the nucleus
  5. Therefore calcium loses its outer electrons more easily, making it more reactive

Key terms in this question

Group 2

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