Explain why metals are good conductors of electricity and have high melting points.

Pearson Edexcel International GCSE Chemistry (4CH1) — 1.8 Metallic crystals · Explain · 4 marks · View as Markdown

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

Metals have a giant lattice structure in which positive ions are surrounded by delocalised electrons.

Model answer (4 marks)

Metals contain delocalised electrons that are free to move.
These delocalised electrons can carry electrical charge, so a metal conducts electricity.
The positive ions are held together by strong electrostatic forces of attraction with the delocalised electrons.
A large amount of energy is required to overcome these strong forces, giving metals high melting points.

Examiner tips

Use the exact phrase ‘delocalised electrons’ and ‘electrostatic forces of attraction’.
Show the link between free electrons and conductivity, and between strong forces and high melting point.
Keep the answer concise – one sentence per point.

Common mistakes

Confusing ‘delocalised electrons’ with ‘free electrons’ without linking to conductivity.
Mentioning only one reason for high melting points, e.g. ‘strong metallic bonds’, without noting the role of delocalised electrons.

Mark scheme (4 marks)

Metals contain delocalised electrons (that are free to move)
These delocalised electrons can carry electrical charge / current through the metal
There are strong electrostatic forces of attraction between the positive ions and the delocalised electrons
A large amount of energy is needed to overcome these strong forces, so the melting point is high

Key terms in this question

conductor