L

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