Between 1908 and 1911, Rutherford showed that the positive part was only 1/3000th of the diameter of the atom.

Models of "planetary" electrons orbiting a nuclear "Sun" were proposed, but cannot explain why the electron does not simply fall into the positive charge. In 1913, Niels Bohr and Ernest Rutherford connected the new atomic models to the mystery of the Rydberg formula: the orbital radius of electrons was constrained