Summary:
- 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.