Diamond is used to make cutting tools. Explain why diamond has a very high melting point and why it cannot conduct electricity.

AQA GCSE Chemistry (8462) — 4.2.3 Structure and bonding of carbon · 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 in diamond forms four covalent bonds with other carbon atoms, creating a giant covalent network.
The network contains many strong covalent bonds, so a large amount of energy is required to break them, giving diamond a very high melting point.
Diamond has no free or delocalised electrons; all electrons are involved in covalent bonds.
Because there are no charged particles free to move, diamond cannot conduct electricity.

Examiner tips

  • Use the term "giant covalent network" to show structure. Mention "strong covalent bonds" to justify high melting point. State "no free/delocalised electrons" to explain lack of conductivity. Keep answer concise and use correct terminology.

Common mistakes

  • Confusing diamond with graphite and saying it conducts electricity. Using "metallic bonding" instead of covalent. Omitting the reason for the high melting point (strong covalent bonds).

Mark scheme (4 marks)

  1. Each carbon atom forms four covalent bonds (with four other carbon atoms)
  2. There are many strong covalent bonds throughout the giant covalent structure, requiring a large amount of energy to break them
  3. There are no free/delocalised electrons in diamond
  4. There are no charged particles free to move, so diamond cannot carry an electrical current

Key terms in this question

diamond

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