P1

P1

1. The History of the atom and atomic structure

   • 1803 John Dalton
     • 1897 J J Thomson
       • He figured out atoms weren't solid spheres
       • His measurements of charge and mass showed that atoms had negatively charged particles - electrons
         • His model was called the Plum Pudding model
       • 1909 Ernest Rutherford, Hans Geiger, Ernest Marsden
         • Conducted the famous gold foil experiment
           • They found that some of the positively charged alpha particles deflected the way it came
             • This made Rutherford to come up with the Nuclear Atom
               • This was most of the mass of the atom is concentrated in a tiny, positive nucleus (the centre), surrounded by a cloud of negative electrons
         • 1912 Niels Bohr
           • He realised that electrons would just be attracted by the nucleus causing it to collapse
           • He Said that electrons are in shells
             • Causing the electrons to have a fixed orbit around the nucleus
               • Each shell had a fixed energy
     • Said that everything was made of tiny sphere particles called atoms
     • These atoms couldn't be broken
   • The Nucleus contains Protons and Neutrons (making the nucleus positive)
     • This was nearly the whole of the mass
     • Electrons whizzed round the nucleus in orbits
     • The rest is mostly made out of nothing
     • The Particle Stats table

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