Question

Classify carbon.

Answer 1

Carbon exists in two different forms i.e. allotropic and amorphous forms.

• Crystalline forms:
  1. Diamond: In diamond, each atom of carbon of the given crystal unit is surrounded by four other carbon atoms, which are joined by covalent bonds, such that they form a regular tetrahedron. The diamond crystal is a compact structure in which atoms of a single unit lie in different planes. Thus, the atoms cannot slip because of their different positions in different planes and hence, diamond is the hardest naturally occurring substance.
  2. Graphite: In graphite, atoms of a single crystal are arranged in a hexagonal ring in a single plane. The bonds between the carbon atoms of two single crystals in the parallel planes are weak. Thus, one plane can easily slide over another plane by applying pressure. This is why graphite is soft and can be used as a lubricant.
  3. Fullerene: It is the third and the most recently discovered allotrope of carbon. Buckminsterfullerene is a cluster of sixty carbon atoms arranged in the form of a football. It is named after the American architect Buckminster Fuller, as it resembled the geodesic dome designed by him. Since it contains sixty carbon atoms, its chemical formula is C₆₀.
• Amorphous/Non-crystalline forms:
  
  1. Coal: It is formed by decomposition of dead remains of plants when they got buried in the land owing to the high temperature and pressure conditions present there. Based on the content of carbon present, normally four types of coal deposits exist and these are as follows:
     • Peat with less than 60% carbon content.
     • Lignite with 60 to 70% of carbon content.
     • Bituminous coal with 70 to 90% carbon.
     • Anthracite is known as the pure form of coal. This coal is hard and contains about 95% of carbon.
  2. Charcoal: It is produced from the bones of animals, combustion of wood etc.
  3. Coke: The pure coal that remains when coal gas has been taken away from coal, is called coke. Coke is used in production of aeriform fuel such as water gas (CO + H₂) and producer gas (CO + H₂ + CO₂ + N₂).