What is the difference between diamond and graphite?
There are differences between diamond and graphite even though they are the same chemically. They both contain carbon but they do not look the same, which is why they are called polymorphs. Polymorphs are substances that have the same chemical composition but are different in appearance. Graphite is opaque and metallic, but diamond is transparent and brilliant. Diamonds have this appearance because of the natural crystal component.
Diamond is the hardest natural substance with a hardness of 10 on the Mohs Scale. Graphite is very soft and has a hardness level of only 1 or 2 on the Mohs Hardness Scale. Because of its softness it is used as lead in pencils and as a lubricant.
The molecular arrangement of both graphite and diamond is different. Each carbon atom in diamond has four adjacent atoms and it is bonded to the adjacent ones. It is possible that this arrangement accounts for its hardness. However, in graphite the individual carbon atoms link up with each other to form a sheet of carbon. Then within each sheet of atoms, each one of them is bonded to three adjacent ones.
Diamonds do not have any free electrons that can wander through the inner structure. This is why they are such good insulators. Graphite does have free electrons and this forms another difference. Diamonds have a high refraction index , but graphite doesn’t.