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• 33
• Metallic Bonding and Properties of Materials


  A bit of a mish mash of a topic now to finish off the section-starting with a bit about bording in al
• Metals have Giant Structures
• Metal elements exist as giant metallic lattice structures
• Mg


  • Mg"
  • Mg
  • Mg Mg"
  • Mg
  • Mg Mg Mg"
  • Mg
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• Metallic Bonding


  • The outermost shell of electrons of a metal atom is delocalised the electrons are free to move about the metal. This leaves a positive metal ion
  • The positive metal ions are attracted to the delocalised negative electrons. They form a lattice of closely packed positive ions in a sea of delocalised electrons this is metallic bonding
• Metals have high melting points because of the strong electrostatic attraction between the positive metal ions and the delocalised sea of electrons
• The number of delocalised electrons per atom affects the melting point. The more there are, the stronger the bonding will be and the higher the melting point
• The delocalised electrons can pass kinetic energy to each other, making metals good thermal conductors
• Metals are good electrical conductors because the delocalised electrons can move and carry a charge
• Metals are insoluble (except in liquid metals), because of the strength of the metallic bands
• Solid


  Particles very close together, high density, incompressible, vibrate about a fixed point
• Liquid


  Similar density to solid, virtually incompressible, particles move about freely and randomly
• Gas


  Particles have more energy and are much further apart, low density, very compressible, particles move about freely with not a lot of attraction between them
• Changing state


  To change from a solid to a liquid or a liquid to a gas, you need to break the forces that are holding the particles together. To do this you need to give the particles more energy, eg. by heating them