deuterium

Deuterium is a stable isotope of hydrogen that contains one proton and one neutron in its nucleus, giving it a mass number of 2. It is commonly denoted as D or 2H. Like ordinary hydrogen, deuterium is the lightest element in its group and occurs in natural hydrogen-bearing substances.

In natural sources, deuterium is present at about 0.015% of hydrogen, with a D/H ratio of roughly 1.6 × 10^-4. Because two deuterium atoms can replace the two protium atoms in water, small amounts of heavy water (deuterium oxide, D2O) form naturally. The distribution of deuterium varies in precipitation and seawater, and it is used in hydrological and climate studies as an isotopic tracer.

Deuterium has nearly identical chemical properties to protium, but its greater mass influences physical properties and reaction rates. Bonds involving deuterium are stronger and vibrate at lower frequencies. Physical differences include a density of about 1.107 g/mL for D2O at room temperature, a melting point of 3.8°C, and a boiling point of 101.4°C, compared with water’s 0°C and 100°C, respectively. These differences affect reaction kinetics and spectroscopic behavior, which makes deuterium valuable in research.

Production and separation of deuterium rely on isotopic enrichment from natural water, using processes such as electrolysis, distillation, or chemical exchange. Industrial methods include the Girdler sulfide process and other exchange techniques to concentrate D.

Applications include tracing and labeling in chemistry and biochemistry, deuterated solvents for nuclear magnetic resonance (NMR) spectroscopy, and the use of heavy water as a neutron moderator in certain nuclear reactors. Deuterium is also explored as a potential fuel in fusion energy research.

Historically, deuterium was discovered by Harold Urey in 1931, and the symbol D derives from the Greek deuteros, meaning second. In small, natural amounts it poses no special hazard, but high concentrations of heavy water can interfere with biological processes.