Describe the trend in reactivity of the alkali metals as you go down Group 1, and explain this trend in terms of atomic structure.

Pearson Edexcel International GCSE Chemistry (4CH1) — 2.1 Group 1 (alkali metals) · Describe and Explain · 4 marks · View as Markdown

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

Lithium, sodium and potassium are all alkali metals found in Group 1 of the periodic table. Each reacts with cold water to produce a metal hydroxide and hydrogen gas.

Model answer (4 marks)

Reactivity increases down Group 1 (Li < Na < K < Rb < Cs). This is because the atoms have more electron shells as you go down the group, so the outermost electron is further from the nucleus. The increased distance and the shielding effect of the inner electrons reduce the attraction between the nucleus and the outer electron, making it easier to lose that electron. Therefore less energy is required to remove the outer electron, so the metals become more reactive.

Examiner tips

  • Use the words "increases" and "down Group 1" to show the trend. Mention the outer electron is further from the nucleus. Explain the role of shielding and reduced nuclear attraction. Link the easier loss of the outer electron to increased reactivity.

Common mistakes

  • Saying the trend is the same for all metals. Forgetting to mention the outer electron is further from the nucleus. Using vague terms like "more reactive" without explaining why.

Mark scheme (4 marks)

  1. Reactivity increases going down Group 1 (from lithium to caesium)
  2. The atoms have more electron shells / the outer electron is further from the nucleus going down the group
  3. The outer electron is more easily lost / less energy is needed to remove the outer electron
  4. Because the attraction between the nucleus and the outer electron decreases (as the electron is shielded / further away)

Key terms in this question

alkali metals · Group 1 · reactivity

Related

More Group 1 (alkali metals) questions

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