Arranged in different hexagonal layers, strong covalent bonds exist between carbon atoms, requiring lots of energy input in order to break. However, only weak inter-molecular forces exist between the different layers of graphite, this explains why it is used in pencils, not much energy needed to break these bonds, layers can easily slide past each other. The one thing that makes graphite stand out is its ability to conduct electricity. Any Carbon in graphite is bonded to only three others (it has the ability to bind to up to 4 because of its valence) this means there are free electrons running throughout the structure, electricity is defined as the flow of electrons and hence this property is what makes graphite a good conductor.