Examples of the inorganic chemistry of carbon allotropes are diamond, graphite and fullerenes.
• Inorganic carbon may exist in the form of diamond. Diamond is crystal clear, isotropic crystal. It is the hardest naturally existing substance on earth. Diamond has four valence electrons, and when each one of the electrons forms bonds with another carbon it forms a sp3-hybridized atom. The boiling point of diamond is 4827°C.
• Unlike diamond, graphite is opaque, spongy, dull and hexagonal. Graphite can act as a conductor (electrodes) or merely as pencils. Graphite is made up of planes of sp2 hybridized carbon atoms in which each carbon is linked to the other three carbons.
• Fullerenes are carbon cages that are denoted with the formula C2n where n > 13. The most available fullerene is the sperical C60. Fullerene might have atoms or molecules within the cage (endohedral fullerenes) or covalently linked outside (exhoedral or adduct fullerenes).