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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 and are formed due to the difference in the arrangement of atoms. These allotropes of carbon are classified into two types. They are
  • Crystaline forms
  • Amorphous forms

Allotropes of carbon have received intensive attention because of their inherited physical fascination and the associated applications of bio-medicine, new material, electronics and energy research.

Allotropes of Carbon

Amorphous forms :

The black residue left when carbon compounds are heated is called amorphous carbon . Different amorphous allotropes of carbon are

  • Coal
  • Coke
  • Wood Charcoal
  • Animal charcoal
  • Lamp black
  • Gas carbon
  • Petroleum coke
  • Sugar charcoal


3 Allotropes of Carbon

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Carbon atoms can arrange themselves into different hybridized chemical bonds and therefore can exhibit very different physical and chemical features such as diamond and graphite. Carbon in the solid phase can exist in three allotropic forms: graphite, diamond and buckminsterfullerene.
  1. Diamonds are transparent crystals with cubic lattice structure. Since each atom bonds of four others tetrahedrally to form a 3-dimensional network under high pressure, the density of diamond ranges from 3.15 to 3.53 g/cm3 almost twice the density of graphite.
  2. Graphite is composed of sp2 carbon forming an infinite planar layer ideally. Within a layer each carbon atom is chemically bonded to three other carbons by using 2px/y hybridized orbital and the un hybridized 2pz orbital of each carbon together forms delocalized $\pi$ bonds and results in fused stable hexagonal rings formation.
  3. Fullerenes have a similar hexagonal planar ring structure as graphite and pentagonal or sometimes heptagonal rings to bend these hexagonal rings into different shapes with positive to negative curvaturs.

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