Allotropes of carbon

Allotropes of carbon

Allotropy is the existence of two or more different physical forms in the same state of a chemical element.

An allotrope is any of the different physical form in the same state into which a chemical element can exist.

Carbon exists in two main allotropes, i.e. graphite and diamond.

Graphite

In graphite, each carbon atom is covalently bonded to 3 carbon atoms to form a layer of hexagons. Each layer is bonded to another by weak van der Waal forces.

Structure of graphite

Properties of graphite as a result of its structure

1. Has open structure and low density.
2. It is slippery and used as a lubricant.
3. Has unbonded π-electron that is free to move about making graphite a good conductor of electricity and heat

 

b. Diamond

Structure of diamond

Each carbon atom is bonded tetrahedrally to four carbon atoms to form a 3D compact structure by strong covalent bonds. As a result diamond has a high density, melting and boiling point. It is the hardest substance known.

 

Diamond is used as an ornament, and to drill and cut other substances.

 Differences between diamond and graphite

1. The density of graphite (2.3 gcm^-3) that of diamond (3.5 g cm^-3)
2. Diamond is very hard while graphite is soft
3. Graphite is slippery while diamond is not
4. Graphite conducts electricity while diamond does not.

Experiment to show that graphite and diamond are allotropes of carbon

When equal masses of graphite and diamond are burn in air, they give equal volume of carbon dioxide.

 

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