Explain why metals are good conductors of electricity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Metals contain a lattice of positive ions (cations). There are delocalised electrons present. The delocalised electrons can move throughout the metal. When a voltage or potential difference is applied, the delocalised electrons move towards the positive terminal, carrying charge.
Examiner tips
- Use the exact phrase "delocalised electrons" and "lattice of positive ions" to match the mark scheme.
- Show the direction of electron flow (towards the positive terminal) to demonstrate understanding of charge transport.
- Include the role of the applied potential difference to justify why electrons move.
- Keep the answer concise – one sentence per point – to fit the 4‑mark allocation.
Common mistakes
- Confusing electrons with ions; forgetting to mention the lattice of cations.
- Using "free electrons" instead of "delocalised electrons". Failing to state the direction of electron movement or the role of the potential difference.
Mark scheme (4 marks)
- Metals contain a lattice of positive ions (cations)
- There are delocalised electrons present
- The delocalised electrons can move throughout the metal
- When a voltage / potential difference is applied, the delocalised electrons move towards the positive terminal, carrying charge
Related
- All Cambridge International IGCSE Chemistry (0620) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →