Describe the structure and bonding in diamond, and explain why diamond does not conduct electricity.

Cambridge International IGCSE Chemistry (0620) — 2.6 Giant covalent structures · Describe and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Each carbon atom is tetrahedrally bonded to four other carbon atoms, forming a three‑dimensional network.
The atoms are linked by strong covalent bonds throughout the entire lattice, giving a giant covalent structure.
There are no free or delocalised electrons in diamond.
Without charge carriers, diamond cannot transfer electrical current, so it does not conduct electricity.

Examiner tips

  • Use the word ‘tetrahedral’ and mention four covalent bonds to show structure.
  • State ‘giant covalent lattice’ to demonstrate bonding. Explain the lack of free electrons as the reason for non‑conductivity.
  • Keep answer concise – 4 points only.

Common mistakes

  • Confusing diamond with graphite and mentioning delocalised electrons. Using ‘ionic’ or ‘metallic’ bonding terms. Omitting the tetrahedral arrangement or the lattice description.

Mark scheme (4 marks)

  1. Each carbon atom is bonded to four other carbon atoms (tetrahedral arrangement / four covalent bonds)
  2. The atoms are held together by strong covalent bonds throughout the entire lattice / giant covalent (lattice) structure
  3. There are no free / delocalised electrons in diamond
  4. Therefore there are no charge carriers to carry / transfer electrical current

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