CARBON AND ITS ALLOTROPES

When it comes to carbon, most people will think of coal. But few will remember what they studied in 10th standard, about the allotropes of carbon, namely Graphite, Diamond and Fullerenes. Let us discuss that in brief.

GRAPHITE: -

Graphite structure

It is the form of carbon in which atoms are arranged hexagonally, layer by layer. It is the most stable form of carbon. Therefore, its formation enthalpy is taken as zero. It conducts electricity as the electrons can move freely.

Lead of pencil is made up of graphite

It is very soft and slippery. Oils cannot be used at high temperature. Therefore, it is used as a lubricant for machines at very high temperature. It is also used as fibres in plastic for great strength. Every layer of graphite has a gap of 340 picometers from each other. Each carbon has sp2 hybridisation.

DIAMOND: -

Structure of Diamond

It is the form of carbon with a crystal structure. It is the hardest substance on earth. The hardness is due to the extended covalent bond. It is used to make jeweller, cutting tools. It is also used in the manufacture of tungsten filaments in light bulbs.

Every carbon atom is bonded to four other carbon atoms. Therefore, each carbon atom has sp3 hybridisation. The bond length is 154 pm. The formation enthalpy of the diamond is 1.9 kJ/mol.

FULLERENES: -

Structure of Fullerence

They are artificially created by heating graphite in an electric arc. Fullerenes are of many types, depending on the number of bonded carbons. Most important of them is the buckminsterfullerene.

It has 60 carbon atoms bonded in it. It has the shape of a soccer ball. The bond length of the single bond is 143.5 pm and that of the double bond is 138.3 pm. Its formation enthalpy is 38.1 kJ/mol. Therefore, it is not found in nature.

There are other forms of carbons like carbon black, coke, etc. But they are not allotropes as they have other components too.

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