Diamond, graphite, graphene and fullerenes

The idea

In diamond each carbon atom forms four covalent bonds, giving a very hard giant structure with a very high melting point; it does not conduct. In graphite each carbon forms three bonds, in layers of hexagons with weak forces between layers, so it is soft and slippery; one electron per atom is delocalised, so graphite conducts. Graphene is a single layer of graphite. Fullerenes are hollow carbon molecules such as buckminsterfullerene (C₆₀); carbon nanotubes are cylindrical fullerenes.

1. Count bonds per carbon atom.
2. Link bonding to hardness and melting point.
3. Link delocalised electrons to conductivity.

Watch out Graphite conducts because of delocalised electrons; diamond has none, so it does not.