Structure + Bonding

Giant Ionic structure - ions

  • bonding between metals + non-metals
  • High melting/boiling point due to the strong electrostatic attraction between oppositely charged ions -- so takes a lot of energy to pull the ions apart.
  • Only conducts electricity when molten or aqueous because their ions are free to move.

Simple molecular structure - molecules

  • bonding between non-metals
  • VERY low melting/boiling point due to the weak intermolecular forces between its molecules -- so it doesn’t take much energy to pull the molecules apart.
  • Does NOT conduct electricity because they have no ions or delocalised electrons to carry a charge.
  • Buckminsterfullerene: has a VERY low melting/boiling point. Buckminsterfullerene
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Giant Covalent structure - atoms

  • bonding between non-metals - special cases (silicon dioxide, carbon diamond, carbon graphite)
  • VERY high melting/boiling point due to many strong covalent bonds -- so takes a lot of energy to pull the atoms apart.
  • MOST don’t conduct electricity as they don’t have any ions or delocalised electrons to carry charge -- because their electrons are shared in covalent bonds.
  • Carbon graphite CAN conduct electricity however, because only three electrons are covalently bonded, leaving the fourth electron delocalised and able to carry charge.

Giant Metallic Structure - cations

  • bonding between metal elements
  • positive metal cations surrounded by a sea of delocalised electrons.
  • High melting/boiling point due to the strong electrostatic attraction between the positively charged metal cations and the sea of delocalised electrons -- so it takes a lot of energy to pull the cations apart.
  • CAN conduct electricity because they have a sea of delocalised electrons which can move to carry charge. It is a good lubricant because its structure has hexagonal layers which slide over each other due to the weak intermolecular force between the layers.