• After the electron and proton were discovered, people began to try to build a picture of the atom.
  • The Thomson model had electrons mixed in with a positive core of some sort that provided electrical neutrality.
  • Rutherford showed that this model was incomplete.
  • He proposed a model of the atomic nucleus which had a solid core.
  • Physicists postulate a strong nuclear force holds the protons and neutrons together in the nucleus of the atoms.
  • The discovery of the neutron helped fill out the picture even more.
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