2. 1922 made fundamental contributions to understanding atomic structure and quantum mechanics The Bohr model of the atom, the theory that electrons travel in discrete orbits around the atom's nucleus. The shell model of the atom, where the chemical properties of an element are determined by the electrons in the outermost orbit. The correspondence principle, the basic tool of Old quantum theory. The liquid drop model of the atomic nucleus. Identified the isotope of uranium that was responsible for slow-neutron fission – 235U. Much work on the Copenhagen interpretation of quantum mechanics. The principle of complementarity: that items could be separately analyzed as having several contradictory properties.
