metals&alloys

• What type of structure do metals consist of?

  Giant structures of atoms arranged in a regular pattern
• What happens to the electrons from the outer shells of metal atoms in metallic bonding?

  They become delocalised and are free to move through the structure
• What results from the sharing of delocalised electrons in metals?

  Strong metallic bonding
• What are the properties of metals explained by their structure and bonding?

  • Electrical conductors due to delocalised electrons
  • Good conductors of thermal energy
  • High melting and boiling points due to strong metallic bonding
• What is an alloy?

  A mixture of two or more elements, at least one being a metal
• Why are alloys often more useful than pure metals?

  Alloys can be made harder by adding another element
• What is pure iron's characteristic in terms of hardness?

  Pure iron is very soft
• What happens when tungsten is added to iron?

  It makes tool steel, which is harder than pure iron
• What are the types of steel and their properties?

  • 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
• How does the structure of a pure metal affect its hardness?

  In a pure metal, layers can slide over each other easily, making it soft
• What happens to the layers of atoms in an alloy when a force is applied?

  The layers require a greater force to slide over each other
• Why are alloys harder and stronger than pure metals?

  Alloys have atoms of different sizes that distort the layers of atoms
• How does the distortion of the metal lattice structure affect alloy properties?

  • Distorted layers require greater force to slide
  • Results in increased hardness and strength of the alloy