Rutherford discovers the atomic nucleus

In 1909, at the University of Manchester, Hans Geiger and Ernest Marsden, working for Ernest Rutherford, fired alpha particles at thin gold foil and found that a small fraction bounced back, a result Rutherford compared to a fifteen-inch shell rebounding from tissue paper. In 1911 he explained it: almost all the mass and the positive charge of an atom are concentrated in a tiny nucleus, with the electrons orbiting far away, so that an atom is mostly empty space. Niels Bohr developed the model in 1913. In 1919 Rutherford split the nitrogen nucleus, the first artificial nuclear reaction.

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