C4 - Metal structure and properties

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  • Created by: Naomi
  • Created on: 23-01-13 20:30
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  • Metal structure and properties
    • Properties of metals
      • Lustrous (shiny)
      • Are hard
        • Strong metalic bonds
      • Have a high density
        • Atoms are closely packed together
      • Have a high melting point
        • A lot of energy is needed to overcome the strong attraction between delocalised elecrons and the positive metal ions
      • Have a high tensile strength
      • Resistant to attacks by oxygen or acid
      • Good conductors of heat and electricity
        • Delocalised electrons
      • Malleable
    • Metallic bonding
      • Metals have high melting points and high boiling points, due to their strong metallic bonds
        • A lot of energy is needed to break the bonds apart
      • When metals conduct electricity, electrons in the metal move
        • Metals conduct electricity because  delocalised electrons within its structure can move easily
      • A metallic bond is a strong electrostatic force of attraction between close-packed positive metal ions and a sea of delocalised electrons
    • Superconductors
      • Superconductors are materials that conduct electricity with little or no resistance
        • Copper, silver and gold all conduct electiricty well, but do not becaome super conductors
      • The electrical resistance of murcury suddenly drops to zero at -268.8 degrees
        • Called superconductivity
      • When a substance goes from its normal state to a superconducting state it no longer has any magnetic fields inside it
        • If a small magnet is rought near the superconductor it is repelled
        • If a small permanent magnet is placed above the superconductor it levitates
      • The potential benefits of superconductors are:
        • Loss-free power transmission
        • Super-fast electronic circuits
        • Powerful electromagnets
      • There needs to be a good deal of development before the true potential of superconductors is realised
        • They only work at very low temperatures, which limits their use
        • Superconductors that function at 20 degrees need to be developed

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