Allotropes of Carbon

Diamond is very hard

• Diamond has a giant covalent structure, made up of carbon atoms that each form four covalent bonds.
  • This makes diamond really hard
• Those strong covalent bonds take a lot of energy to break and give diamonds a very high melting point
• It doesn’t conduct electricity because it has no free electrons or ions

Graphite contains sheets of hexagons

• In graphite, each carbon atom only forms three covalent bonds creating sheets of carbon atoms arranged in hexagons

• There aren’t any covalent bonds between the layers-they’re only held together weakly, so they’re free to move over

  • This makes graphite soft and slippery, so it’s ideal as a lubricating material

• Graphite’s got a high melting point-the covalent bonds in the layers need loads of energy to break

• Only three out of each carbon’s four covalent electrons are used in bonds, so each carbon atom has one electron that’s delocalised(free) and can move

• So graphite conducts electricity and thermal energy

Graphene is one layer of graphite

• Graphene is a sheet of carbon atoms joined together in hexagons
• The sheet is just one atom thick, making it two-dimensional compound
• The network of covalent bonds makes it very strong
  • It’s also incredibly light, so can be added to composite materials to improve their strength without adding much weight
• Like graphite, it contains delocalised electrons so can conduct electricity through the whole structure
  • This means it has the potential to be used in electrons

Fullerenes form sphere and tubes

• Fullerenes are molecules of carbon, shaped like closed tubes or hollow balls
• They’re mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons(rings of five carbon atoms) or heptagons(rings of seven carbon atoms).
• Fullerenes can be used to ‘cage’ other molecules
  • The fullerenes structure forms around another atom or molecule, which is then trapped inside
  • This could be used to deliver a drug into the body
• Fullerenes have a surface area, so they could make great industrial catalysts, individual catalyst molecules could be attached to the fullerenes
• Fullerenes also make great lubricants
• Buckminsterfullerene was the first fullerene to be discovered and it’s got the molecular formula C60 and forms a hollow sphere