Graphite is a giant covalent structure. It is made of hexagonally arranged carbon atoms covalently bonded together. Each carbon atom uses three of the outer electrons to form three covalent bonds with three other carbon atoms.The layers are held together by weak London forces.The spare electron is delocalised within each layer. The delocalised electrons can move along the layers, so graphite is an electrical conductor.Graphene is a single layer of graphite, one atom thick. It is very strong and conducts electricity because of its delocalised electrons.