Deuterium was discovered by Harold C. Urey in 1931. Urey, who won the Nobel Prize in chemistry in 1934 for his discovery, also played a significant role in the development of the atom bomb, serving as the director of war research for the Manhattan Project at Columbia University.
Deuterium, also known as heavy hydrogen, is one of two stable isotopes of hydrogen. The nucleus of a deuterium atom contains one proton and one neutron. The more common form of hydrogen has no neutrons in its nucleus. At the time of deuterium's discovery, the neutron was unknown. Deuterium is used to make the heavy water used in nuclear reactors.