Atomic structure

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  • Atomic structure
    • Mass number: the number of protons + neutrons
    • Current Atomic Model
      • Nucleus contains protons and neutrons
        • neutrons have no charge they have an atomic mass of 1
        • protons are + they have an atomic mass of 1
      • radius about 10^-10 m
      • Nucleus surrounded by shells containing electrons
        • Electrons are negative they have an atomic mass of 1/2000
    • Isotopes
      • Contain different number of neutrons
      • Contain the same number of protons
      • e.g.      Carbon 12,  Carbon 14
      • Different forms of the same element
    • Atomic number: the number of protons
    • Development of the atom model
      • The Greeks were the first to think that matter was made of particles
      • 1804 John Dalton
        • Each element was made of a different type of atom
        • 1897 JJ Thomson
          • Plum Pudding Model
          • Discovered electrons
          • 1909 Rutherford
            • Alpha particle scattering experiment
              • Most of the atom must be empty space because most alpha particles passed straight through the gold foil.
              • The nucleus must be positively charged as alpha particles were repelled and deflected by large angles
              • The nucleus must be very small as very few alpha particles were deflected back.
            • Further developments
              • Neils Bohr: electrons orbit at certain distances called energy levels
              • Chadwick proved the existence of the neutron


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