History of the atom

  • Created by: m.turner
  • Created on: 16-05-18 19:53
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  • History of the Atom
    • 1st = Dalton
      • Described the atoms as solid spheres. Said that different spheres made up different elements.
    • 2nd = JJ Thompson
      • Concluded that they weren't solid spheres. He showed that an atom must contain smaller, negatively charged particles (due to charge and mass) - electrons
      • His theory = the plum pudding model - a ball of positive charge with electrons stuck in it.
    • 3rd = Rutherford
      • Conducted the alpha particle scattering experiment - fired positively charged alpha particles through thin gold foil
      • Some particles passed straight through, some got slightly deflected and some got fired back = plum pudding could not be right.
      • Came up with the idea of the nuclear model of the atom = a tiny, positively charged nucleus at centre, where most of the mass is concentrated.
        • A cloud of negative electrons surrounds this nucleus - so most of the atom is empty space. Shown through being deflected when fired at the nucleus (showing there's positive charge)
    • 4th = Bohr
      • Scientists realised that the 'cloud' of negative would be attracted to the nucleus causing it to collapse.
      • Bohr proposed that electrons orbit around the nucleus in shells - each shell is a fixed distance.
      • Was supported by many experiments.
    • Further Experiments
      • Showed that the nucleus can be divided into smaller particles = have the same charge as a hydrogen nucleus
      • JAMES CHAWICK = provided evidence of a neutral particle - neutron


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