Describe how the reactivity and melting point of the Group I metals change as you go down the group from lithium to caesium. Explain why reactivity changes in this way.

Cambridge International IGCSE Chemistry (0620) — 8.2 Group I properties · Describe and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Reactivity increases down the group because each element has one outer‑shell electron that is lost in reactions. The outer electron is further from the nucleus, shielded by more inner electrons, so the nuclear attraction is weaker and it is more easily lost.

Melting point decreases down the group because the larger atoms have weaker metallic bonding.

Examiner tips

  • Use the word ‘increases’ and ‘decreases’ to match the marks. Mention the single outer‑shell electron and shielding. Explain the weaker nuclear attraction. Include the melting point trend explicitly.

Common mistakes

  • Confusing the trend for reactivity or melting point. Forgetting to mention the single outer‑shell electron. Using ‘more electronegative’ instead of ‘more easily lost’.

Mark scheme (4 marks)

  1. Reactivity increases going down Group I
  2. Melting point decreases going down Group I
  3. Each element has one outer-shell electron that is lost / transferred during reactions
  4. Going down the group the outer electron is further from the nucleus / is more easily lost because there is more shielding / the nuclear attraction is weaker

Key terms in this question

Group I · reactivity · melting point

Related

More Group I properties questions

▶ Try answering this question with AI marking (free) →