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Allotropes of Carbon:Carbon exists in two Allotropic forms,Crystalline allotropes, amorphous allotropes, Crystalline allotropes: Diamond, Graphite, Fullerenes, Amorphous allotropes: Carbon block lamp block, Coke, Charcoal.
Diamond:It has a crystalline lattice. In diamond each carbon atom undergoes sp3 hybridisation.Each carbon is linked to four other carbon atoms in a tetrahedral fashionthrough a sigma bond.The C−Cbond length = 154 pm. It has rigid covalent bond network which is difficult tobreak.It is the hardest substance on earth and it has very high melting point.It acts as an electrical insulator.
Graphite:It has layered structure and these layers are held by vanderwaal forces.In graphite each carbon item undergoes sp2Hybridization.Each carbon is bonded to three other carbon atoms through a sigma bond.The fourth electron forms a ‘Pai’ bond. The C−C bond length within the layer = 141.5 pm. Each layer is composed of hexagonal rings of C-atoms.It is quite soft and its layers can separated easily. It is a good conductor of electricity
Fullerenes: These are discovered by H.W Kroto, E. Smalley and R.F curl.These are made by heating. Graphite in an electric arc. In the presence of inert gas Helium or Argon.They are cage-like structures or soccerball .It is called Buckminister fullerene.All the carbon atoms are sp2 hybridised. And it has both single and double bonds.C−C bond length = 143.5 pm. C=C bond length = 138.3 pm. C60 contains 20 six-membered rings and 12 five-membered rings.Spherical fullerenes are also called bucky balls.Carbon block, Coke, Charcoal.
Carbon Block:It is is obtained by burning hydrocarbons in a limited supply of air.
Charcoal and Coke: By heating wood or coal at high temperatures in the absence of air, charcoal and coke are obtained.