On the constitution of atoms and molecules

by Niels Bohr

, and the distance apart of the nuclei

. The radial force acting on one of the electrons and due to the attraction from the nuclei and the repulsion from the other electron is

Let us now consider a slow displacement of the system during which the radial force balances the centrifugal force due to the rotation of the electrons, and the angular momentum of the latter remains constant. Putting

, we have seen on [p. 55] that the radius of the ring is inversely proportional to

. Therefore, during the displacement considered,