Why Graphite (Carbon) Conducts Electricity

Chemistry Homework
In general, carbon is a nonconductor. Graphite is one of the forms of solid carbon. In graphite, one of the outer electrons of the carbon atom is not involved in the crystal bonding of the solid. That electron is somewhat free to move, and graphite therefore can conduct an electrical current, but it conducts much more poorly than metals. Graphite is used to make carbon resistors, which conduct electricity but with higher resistance. A diamond, which is a different crystalline form of carbon, does not conduct electricity.

Materials such as metals, conduct electricity do so because when their atoms are arranged together in a solid, they have loosely bound electrons which can easily move through the material if an electric potential is applied to it.

For instance, in a copper lattice, there is about one free electron Available per atom of copper for conduction, which makes it a very good conductor. But, carbon holds on more tightly to its electrons so they are not as free to move from place to place as in the case of copper or other metals. It is one of a number of elements known as semiconductors. Its neighbor, one row down on the periodic table, is silicon, which is used for most commercial microchips produced today.

In a semiconductor, electrons can't just flow through the material. They
have to move from atom to atom in "jumps", according to the laws of quantum mechanics. When they jump, they leave a positively charged "hole", which can be later filled by another electron jumping in to take the first electron's place. Under the influence of an electric potential, one sees a slow movement of negatively charged electrons in one direction and positively charged "holes" in the other direction.

If you warm up a semiconductor, the outer electrons are more energetic, and can more easily jump...