In 1912 Bohr joined Rutherford. He realized that Rutherford's model wasn't quite right ... to the periodic repetition of properties of the elements. The shells in which electrons orbit have ...

In 1913, Niels Bohr revised Rutherford's model by ... atom of that element. Therefore, electrons cannot be arranged at random, but they must have fixed levels of energy within each type of atom.

In Chemistry such systems are known as the Bohr model, whereas in particle physics they are known as the Rotating Lepton ...