Metallic Bonding

High melting and boiling points

• Most metals have high melting and boiling points
• The electrostatic attraction between the positive metal ions and the delocalised electrons is strong
• Breaking apart the lattice needs a large amount of energy, so the melting and boiling temperatures are high
  • Group 1 metals are partial exceptions (sodium melts at about 98 °C) because the attraction is weaker when each atom only releases one electron

Electrical and thermal conductivity

• Metals conduct electricity in both the solid and the liquid state
  • The delocalised electrons are free to move through the lattice
  • When a voltage is applied, they drift toward the positive terminal and carry the charge
• Metals also conduct heat well
  • The delocalised electrons gain kinetic energy at the hot end and pass it rapidly through the structure

Malleability and ductility

• Metals are malleable: they can be hammered into shape
• Metals are also ductile: they can be drawn into wires
• Both properties follow from the same feature of the lattice
  • The metal atoms/ions sit in layers
  • Applying a force lets the layers slip past one another into a new arrangement
  • The delocalised electrons rearrange around the shifted ions, so the metallic bonding survives the change of shape
  • The metal changes shape without breaking