Explain why the metallic character of elements increases down Group 1 of the periodic table.

IB DP Chemistry Standard Level (2023 syllabus) — S3.1 The periodic table: classification of elements · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Going down Group 1 the number of electron shells increases, so the outer (valence) electron is further from the nucleus and the atomic radius grows. The additional inner shells also shield the valence electron from the nucleus, reducing the effective nuclear charge it experiences. Consequently the outer electron is more easily lost, giving a lower ionisation energy and therefore a greater metallic character.

Examiner tips

  • Use the phrase ‘effective nuclear charge’ and ‘shielding’ to show understanding of the concept.
  • Show the chain: more shells → larger radius → more shielding → lower ionisation energy → more metallic behaviour.
  • Keep the answer concise – 4 marks, so one sentence per point is enough.
  • Use UK spelling (e.g. ‘shielding’, ‘effective’).

Common mistakes

  • Confusing ‘atomic radius’ with ‘ionic radius’ or omitting the shielding effect.
  • Writing ‘more shells means a stronger attraction’ – the opposite of the correct trend.
  • Using vague terms like ‘easier to lose’ without linking to ionisation energy or metallic character.

Mark scheme (4 marks)

  1. Going down Group 1, the number of electron shells (energy levels) increases.
  2. The outer (valence) electron is further from the nucleus, so the atomic radius increases.
  3. There is increased shielding/screening of the outer electron by inner electron shells, reducing the effective nuclear charge experienced by the valence electron.
  4. The outer electron is therefore more easily lost, giving a lower ionisation energy, which is characteristic of greater metallic behaviour.

Key terms in this question

metallic character

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