Carbon can exist in many different forms. Carbon can exist in these forms:

• graphite
• diamond
• C₆₀ fullerene

Graphite

Structure and Bonding

• Graphite forms a giant covalent structure.
• Each carbon atom is covalently bonded to 3 other carbon atoms.
• Carbons form layers of hexagonal rings.
• The layers are joined by weak intermolecular forces.
• Since only 3 outer electrons are used to form covalent bonds, 1 electron from each carbon atom becomes delocalised.

• Slippery
  • The layers are held by weak intermolecular forces, so layers can easily slide over each other.
• High melting and boiling point
  • Graphite forms a giant covalent structure with many strong covalent bonds. A lot of thermal energy is needed to break the bonds. 
• Conductor of electricity
  • The delocalised electron can move freely within each layer, so graphite can conduct electricity.

• lubricant
• electrodes for electrolysis

Diamond

Structure

• Diamond forms a giant covalent structure.
• Each carbon atom is covalently bonded to 4 other carbon atoms

• Hard
  • Since diamond is a rigid structure held by strong covalent bonds, it is one of the world's hardest materials.
• High melting and boiling point
  • Diamond forms a giant covalent structure with many strong covalent bonds. A lot of thermal energy is needed to break the bonds. 
• Does not conduct electricity
  • All 4 outer shell electrons of carbon are used to form covalent bonds, so there is no delocalised electron to conduct electricity.

• cutting tool
• jewelry

C₆₀ Fullerene

Structure and Bonding

• C₆₀ fullerene has a molecular structure formed by 60 carbon atoms. (It is not a giant covalent structure!!)
• The shape of the molecule is spherical.
• Each carbon atom is covalently bonded to 3 other carbon atoms.
• Since only 3 outer electrons are used to form covalent bonds, 1 electron from each carbon atom becomes delocalised.
• There are weak intermolecular forces between each fullerene molecule.

Properties

• Soft and slippery
  • The weak intermolecular forces between fullerene molecules are broken down easily, so fullerene is soft and slippery.
• Low melting and boiling point
  • Only a small amount of heat energy is needed to overcome to weak intermolecular forces between molecules.
• Conductor of electricity
  • The delocalised electron is mobile, so fullerene can conduct electricity.

• Drug delivery system in the body
• Lubricant

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