Explain why elements in the same group of the periodic table have similar chemical properties, and why metallic character increases going down Group 1.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The periodic table organises elements into groups and periods. Elements in the same group share similar chemical properties, yet there are also clear trends in behaviour as you move down a group.
Model answer (5 marks)
Elements in the same group have the same number of valence electrons, which determines how they react and form bonds. Therefore they show similar chemical behaviour.
Going down Group 1 the atoms have more electron shells. The outermost electron is in a higher‑energy shell, further from the nucleus, and is shielded by the inner electrons. This reduces the effective nuclear charge felt by the outer electron, making it easier to remove. Consequently the metallic character and reactivity increase down the group.
Going down Group 1 the atoms have more electron shells. The outermost electron is in a higher‑energy shell, further from the nucleus, and is shielded by the inner electrons. This reduces the effective nuclear charge felt by the outer electron, making it easier to remove. Consequently the metallic character and reactivity increase down the group.
Examiner tips
- Mention valence electrons first, then link to reactivity.
- Explain shielding and distance of outer electron to justify increased metallicity.
- Use the phrase "more reactive" or "more metallic" to match the mark scheme.
- Keep the answer concise – 5 marks only.
Common mistakes
- Confusing group trends with period trends.
- Failing to mention shielding or distance of the outer electron.
- Using vague terms like "similar properties" without linking to valence electrons.
Mark scheme (5 marks)
- Elements in the same group have the same number of electrons in their outer shell (same number of valence electrons)
- The number of outer shell electrons determines how an element reacts / forms bonds, so elements in the same group react in a similar way
- As you go down Group 1, atoms have more electron shells / the outer electron is in a shell further from the nucleus
- There is more shielding of the outer electron from the nuclear charge by inner electron shells
- The outer electron is lost more easily, so the element becomes more reactive / more metallic going down Group 1
Key terms in this question
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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