# Allotropes of Carbon

Carbon with atomic number 6 and represented by the symbol ‘C’ in the periodic table is one of the most influential elements we see around us. Carbon is one of the elements which shows allotropy. Allotropic of carbon can be either amorphous or crystalline. Carbon due to its capability of having variable oxidation states and/or coordination number makes carbon one of the few elements to have multiple numbers of allotropic forms. Carbon’s ability to catenate is another contributing factor. Thus this leads to various allotropes of carbon.

## Allotropes of carbon

• Diamond – an extremely hard, transparent crystal, with the carbon atoms arranged in a tetrahedral lattice. A poor electrical conductor. An excellent thermal conductor.
• Lonsdaleite – also called hexagonal diamond.
• Graphene – is the basic structural element of other allotropes, nanotubes, charcoal, and fullerenes.
• Q-carbon – a ferromagnetic, tough, and brilliant crystal structure that is harder and brighter than diamonds.
• Graphite – a soft, black, flaky solid, a moderate electrical conductor. The C atoms are bonded in flat hexagonal lattices (graphene), which are then layered in sheets.
• Linear acetylenic carbon (Carbyne)
• Amorphous carbon
• Fullerenes, including Buckminsterfullerene, a.k.a. “buckyballs”, such as C60.
• Carbon nanotubes – allotropes of carbon with a cylindrical nanostructure.

Let us take a look into the more widely known allotropes of Carbon, Graphite, and Diamond.

### Graphite

Graphite is a soft, black and slippery solid. This property of graphite persists because it cleaves easily between the layers. It also has metallic luster which helps in the conduction of electricity. Graphite is widely used as a lubricant only because of its soft and slippery nature. One of the most important properties of graphite is that it is used as a dry lubricant for machines at high temperature where we cannot use oil. Graphite is used to make crucibles which have the property that they are inert to dilute acids as well as alkalis. Graphite has a unique honeycomb layered structure. Each layer is composed of planar hexagonal rings of carbon atoms in which carbon-carbon bond length within the layer is 141.5 picometers. Out of four carbon atoms three forms sigma bonds whereas the fourth carbon forms pi-bond. The layers in graphite are held together by Vander Waal forces.

Graphite Structure

### Diamond

Diamond is another important allotrope of carbon. These are used to make precious jewelry because of its brilliant shining property. They are also used as a tool for cutting glass because of its hardness. In diamonds, each carbon atoms has sp3 hybridization and forms covalent bonds with four other carbon atoms at the corners of the tetrahedral structure. A diamond of good gem quality will contain a vast number of carbon atoms that are bonded by a covalent bond in one molecule. Diamond was the hardest material known to man at one point in time, but stronger materials have been discovered now like carbyne and advanced geometrical forms of graphene.

Diamon Structure

#### Do you know why a diamond is hard?

It is hard because breaking a diamond crystal involves rupturing a large number of strong covalent bonds. Breaking Covalent bonds is no easy task, just this property makes diamond hard.

### Buckminsterfullerene

Buckminsterfullerene ($C_{60}$) is also one of the allotropes of carbon. The structure of fullerene is like in a cage shape due to which it looks like a football.

Buckminsterfullerene Structure

For further information on the other allotropic forms of carbon, allotropic forms of phosphorous and more, sign up with Byju’s and then download Byju’s- the learning app.

#### Practise This Question

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