Quantum mechanics and atomic theory matured in the 1920s through brilliant contributions from scientists including the French physicist Louis Victor de Broglie (1892–1987), the British physicist Paul Dirac (1902–1984), the Austrian physicist Erwin Schrödinger (1887–1961), and the German theoretical physicist Werner Heisenberg (1901–1976). Other researchers began to construct machines, called particle accelerators, that allowed them to hurl high-energy subatomic particles at target nuclei in an organized and somewhat controllable attempt to unlock additional information about the atomic nucleus. For example, in 1932, the English physicist Sir John Cockcroft (1897–1967) and the Irish physicist Ernest Walton (1903–1995) used an “atom smasher” (a linear particle accelerator) to produce the first artificial disintegration of an atomic nucleus. They bombarded target lithium nuclei with high-energy protons, and the resulting nuclear reaction validated Einstein’s energy-mass equivalence principle. Their pioneering work also demonstrated the important role accelerators would play in nuclear physics in the decades to come. At about the same time, Lawrence began using his newly invented cyclotron for nuclear research at the University of California in Berkeley. With a succession of ever more powerful machines, Lawrence attracted an outstanding team of nuclear scientists to Berkeley, including the American chemist-physicist Glenn T. Seaborg (1912–1999), who discovered plutonium in 1940. From the 1930s through the early 1960s, scientists developed the technical foundation for modern nuclear technology, including the nuclear reactor and the nuclear weapon, as well as many other interesting applications of nuclear energy. In the process, scientists and engineers used a nuclear model of the atom that assumed the nucleus contained two basic building-block nucleons: protons and neutrons. This simple nuclear atom model (based on three so-called elementary particles: the proton, the neutron, and the electron) is still very useful today for general discussions concerning nuclear science and nuclear technology applications.
Nucleus, Atom and Nuclear Atom
