Properties of metals

• • electrical conductors - their delocalised electrons carry electrical charge through the metal
  • good conductors of thermal energy - their delocalised electrons transfer energy
  • high melting and boiling points - the metallic bonding in the giant structure of a metal is very strong - large amounts of energy are needed to overcome the metallic bonds in melting and boiling
  • malleable (they can be bent and shaped easily). In pure metals, the atoms are arranged in neat layers, and when a force is applied to the metal, the layers of metal atoms can slide over each other, giving the metal a new shape
• An alloy is a mixture of two or more elements, where at least one element is a metal. Many alloys are mixtures of two or more metals.
• • mild steel = carbon and iron = easy to bend and pull into wires
  • tool steel = tungsten and iron = hard, can be heated to high temperatures
  • stainless steel = chromium and iron = hard, does not rust easily
• Explaining alloy hardness: solid state

  • a pure metal has a giant metallic structure
  • the atoms are arranged in layers
  • when a force is applied, the layers may slide over each other
  • the harder and stronger the metal, the greater the force is needed to change or bend it
• Explaining alloy hardness: pure metal

  • the forced needed to make the layers slide over each other is small
  • this explains why many pure metals are soft