deuterio

Deuterium, symbol D or 2H, is a stable isotope of hydrogen with one proton and one neutron. Its atomic mass is about 2.014 u. In nature it occurs at a relative abundance of about 0.0156% of hydrogen (roughly 156 parts per million). In water, about 0.015% of the hydrogen atoms are deuterium, and the corresponding heavy water species (D2O) has higher isotopic content when enriched. The deuteron has spin 1 and a binding energy of 2.224 MeV.

Deuterium was discovered in 1931–1932 by Harold Urey through the study of water electrolysis; it was named deuterium from the Greek deuteros, “second.” It is a non-radioactive, stable isotope.

Applications include the use of heavy water (D2O) as a neutron moderator in some nuclear reactors (notably CANDU reactors). Deuterium is also used as a tracer in chemistry and hydrology, and deuterated solvents (such as D2O and CDCl3) are common in NMR spectroscopy; isotopic labeling helps study reaction mechanisms and metabolism.

Cosmology relies on deuterium measurements because deuterium is produced in Big Bang nucleosynthesis and destroyed in stars; the D/H ratio in primordial gas provides constraints on the baryon density of the universe. Deuterium is observed in interstellar gas and in comets and is used as a cosmological probe.

Safety: Deuterium and heavy water are not radioactive. Normal concentrations pose little hazard, but significant replacement of body water with D2O can disrupt biological processes and may be harmful.