  The atomic model that Niels Bohr suggested in 1913 celebrated its greatest
victories in connection with one-electron atoms. Among them were the isotopic
spectral effect and what became known as Rydberg atoms, insights that were
fully recognized only many years later. He considered the original ring model a
first step towards an understanding of atomic structure, and during the
following years he developed it into more ambitious models that, he hoped,
would also describe many-electron atoms. His theory of the periodic system
marked the culmination of the orbital atom within the framework of the old
quantum theory. However, the theory would soon be replaced by more symbolic
models that heralded the coming of the quantum-mechanical atom.
