arxiv.org: The many faces of the Bohr atom. Helge Kragh. Centre for Science Studies, Department of Physics and Astronomy, Aarhus University. Citat: "...Bohr’s theory of 1913 was much more than just a theory of the hydrogen atom. In the second part of the trilogy he ambitiously proposed models also of the heavier atoms, picturing them as planar systems of electrons revolving around the nucleus. The lithium atom, for example, would consist of two concentric rings, an inner one with two oppositely located electrons and an outer one with a single electron...However, latest by 1920 it was realized that the planar ring atom was inadequate and had to be replaced by a more complex model that made both chemical and physical sense.13...In the Bohr-Kramers-Slater (BKS) theory from 1924, describing the atom as an orchestra of virtual oscillators, the electrons orbiting in stationary states had finally disappeared...."
