Niels Bohr won the 1922 Nobel Prize in Physics for developing a model of the atom.
Bohr proposed in 1913 that electrons occupy specific allowed orbits, or stationary states, around an atomic nucleus. An electron could move between these energy levels by absorbing or emitting a discrete amount of radiation. This model explained important features of hydrogen’s spectrum and helped establish early quantum theory.
The Nobel committee honored Bohr “for his services in the investigation of the structure of atoms and of the radiation emanating from them.” His model improved on Ernest Rutherford’s nuclear model, which had not explained why orbiting electrons did not continuously lose energy and spiral into the nucleus.
Bohr’s model was later replaced by quantum mechanics, in which electrons are described by probability distributions rather than fixed planetary-style orbits. Nevertheless, the Bohr model remains a useful introductory picture for energy levels and atomic spectra.