Have you ever wondered why graphite conducts electricity and diamond does not?

One 2s and two 2p atomic orbitals undergo hybridization in graphite to form a hybridized sp2 orbital that has a trigonal planar geometry. These hybridized orbitals form sigma bonds between neighboring carbon atoms to produce a hexagonal network of carbon atoms within a graphite sheet. One of the 2p atomic orbitals of each carbon atom overlaps with those of its neighbors to form the pi bonding system. It is the delocalization of electrons within the pi bonding system that is responsible for the graphite's ability to conduct electricity. The bonding of the carbon atoms within graphite is schematically shown below:

This figure shows how one of the 2p of each carbon atom is situated relativeto its neighbors.

The sideway overlapping of 2p orbitals between neighboring carbon atoms form a pi bonding system where a "cloud" of electrons can move about.