Allotropes of Carbon

• Allotrope - made of the same substance but arranged differently

Diamond

• Carbon atoms forms four covalent bonds
• Rigid covalent structure
• High melting/boiling point as every strong covalent bond must be broken to seperate the atoms, this takes a lot of energy
• Does not conduct electricity as no delocalised electrons

Graphite

• Carbon atoms forms three covalent bonds
• In layers making a giant covalent structure
• High melting/boiling point as it involves breaking many strong covalent bonds to seperate the atoms
• Between each layer are weak intermolecular forces of attraction
  • Easily broke so the layers can slide over each other, making it soft
• Each carbon atom provides a delocalised electron (due to the 3 bond made)
  • Means graphite can conduct electricity

Graphene

• Structure resembles a single layer of graphite
• High melting point and very strong due to its large regular arrangement of carbon atoms joined by covalent bonds
• Each carbon atom provides a delocalised electron (single layer of graphite = 3 bonded carbon)
  • Graphene can conduct electricity

Fullerenes

Buckyballs

• Spherical form of carbon atoms
• Made of large molecules, not classed as giant covalent structure
• Weak intermolecular forces exist between buckyballs
  • These need little energy to overcome
    • Substances containing buckyballs are slippery and have lower melting points than graphite and diamond

Nanotubes

• Resembles a layer of graphene rolled into a tube shape
• High tensile strength
  • Strong in tension
    • Resistant to being stretched
• Like graphene, nanotubes are strong and conduct electricity because they have delocalised electrons