Allotropes of Carbon

• In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure
• The strong covalent bonds in diamonds make the material hard, and means that the melting and boiling point is high
• Diamond does not conduct electricity because it has not free electrons or ions
• In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers
• In graphite, one electron from each carbon atom is delocalised so it can conduct electricity like metals
• Graphite has a high melting and boiling pinot because the covalent bonds in the layers need a lot of energy to break
• Since the layers of graphite are held together weakly they can move over each other making it useful as a lubricant
• Graphene is a single layer of graphite and has properties that make it useful in electronics and composites
• Graphene is a conductor of electricity
• Fullerenes are molecules of carbon atoms with hollow shapes
• The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms
• The first fullerene to be discovered was Buckminsterfullerene (C$_{60}$) which has a spherical shape
• Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios
• The properties of carbon nanotubes make them useful for nanotechnology, electronics and materials