Deuterium is a stable isotope of the element hydrogen. An atom of deuterium consists of one proton, one neutron and one electron. About .015% of natural hydrogen is composed of deuterium. Discovered by Harold C. Urey in 1932.
Deuterium is frequently represented by the chemical symbol D. Since it is an isotope of hydrogen with mass number 2, it is also represented by 2H. IUPAC allows both D and 2H, although 2H is preferred. A distinct chemical symbol is used for convenience because of the isotope's common use in various scientific processes.
