Diamond and graphite are both giant covalent structures made only of carbon atoms. Why does graphite conduct electricity but diamond does not?
The atoms in graphite carry a small charge, but the atoms in diamond carry no charge.
One outer electron per atom is delocalised in graphite, but all four are bonded in diamond.
The covalent bonds in graphite are weaker, so electrons can break away from the atoms.
The layers in graphite are further apart, so electrons have room to move between them.
40 exam-style questions on AQA GCSE Chemistry 2.3 Structure and bonding of carbon, covering 2.3.1 Diamond, 2.3.2 Graphite, and 2.3.3 Graphene and fullerenes. Each one has a worked solution and a mark scheme showing where the marks go.