: an isotope of hydrogen that has one proton and one neutron in its nucleus and that has twice the mass of ordinary hydrogen—called also heavy hydrogen
Isotope of hydrogen, chemical symbol 2H or D, atomic number 1 (but atomic weight approximately 2). Harold C. Urey won a Nobel Prize for its discovery and isolation. Its nucleus contains one proton and one neutron. A stable substance found in naturally occurring hydrogen compounds to the extent of about 0.015%, deuterium can be purified by distillation of hydrogen or by electrolysis of water. It enters into all the same chemical reactions as ordinary hydrogen; it forms D and HD, analogous to molecular hydrogen (H), and DO (heavy water), analogous to ordinary water (HO). Nuclear fusion of deuterium atoms or of deuterium and tritium at high temperatures releases enormous amounts of energy. Such reactions have been used in nuclear weapons and experimental power reactors. Deuterium is useful as a tracer in research into reaction mechanisms and biochemical pathways.