On the quantum theory of radiation and the structure of the atom

by Niels Bohr

are the electric charges and the masses of the nucleus and the electron respectively. The frequency of rotation and the major axis of the relative orbit of the particles in the stationary states are given by

The energy necessary to remove the electron to infinite distance from the nucleus is

This expression is also equal to the mean value of the kinetic energy of the system. Since

is equal to the total energy

of the system we get from (4) and (5)