Question

What are allotropes of carbon. Give a long notes on Allotropes of carbon

Answer 1

Allotropes of carbon :-

• The property of an element to exist in two or more physical forms having more or less similar chemical properties but different physical properties is called allotropy.

• The different forms of the element are called allotropes.

• Allotropy arises due to difference in the arrangement of atoms in the molecules.

• Coal, coke, charcoal, gas carbon, lamp black, etc., are amorphous forms of carbon.

• Diamond, graphite and buckminister fullerene are crystalline forms of carbon.

Diamond :-

• Carbon in diamond undergoes $\mathsf{{sp}^{3}}$ hybridisation.

• Arrangement of carbon in diamond is tetrahedral.

• Diamond is hardest substance. The hardness of diamond is use due to strong C-C bonds.

• Diamond is non-conductor of electricity due to absence of free electrons.

• Bond angle is 109° 28' and bond length is 1.54 A°

Graphite :-

• Graphite has carbon atoms arranged in layers.

• Carbon atom undergoes $\mathsf{{sp}^{2}}$ hybridisation and arranged in trigonal planar arrangement.

• Bond angle is 120° and bond length 1.42 A°

• Pure 'p' orbital in carbon atoms to form delocalised $\pi$ system.

• Graphite is a good conductor of electricity due to presence of free electrons.

• Two layers in graphite are separated by 3.35 A° and attracted by weak forces called London dispersion forces.

• Graphite is used as lubricant and as 'lead' in pencils.

Buckminster fullerene :-

• These are discovered by F. Curl, Harlod W. Kroto and Richard E. Smalley.

• The molecules composed of carbon in the form of hollow sphere (soccer like), ellipsoid, or tube shape are called Buckminsterfullerene ( $\mathsf{_{60} C})$

• Spherical fullerenes are also called buckyballs.

• ($\mathsf{_{60} C}$)contains 12 pentagonal and 20 hexagonal rings with each carbon $\mathsf{{sp}^{2}}$ hybridized.

• Fullerenes are used an specific antibiotics to target resistant bacteria and melanoma cancer cells.

Nanotubes :-

• These are allotropic form of carbon discovered by Sumio li jima.

• Nanotubes consists of hexagonal arrays of covalently bonded carbon atoms to form sheets, which are rolled into cylinders.

• These are electrical conductors and used as molecular wires.

• These are used in integrated circuits instead of copper.

• These are also used to inject biomolecules into a single cell.

Answer 2

Answer:

Carbon is capable of forming many allotropes (structurally different forms of the same element) due to its valency. Well-known forms of carbon include diamond and graphite. ... Larger scale structures of carbon include nanotubes, nanobuds and nanoribbons.

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