Deuterium

Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). Deuterium thus accounts for approximately 0.015% (on a weight basis, 0.030%) of all naturally occurring hydrogen in the oceans on Earth (see VSMOW; the abundance changes slightly from one kind of natural water to another). Deuterium abundance on Jupiter is about 6 atoms in 10,000 (0.06% atom basis); these ratios presumably reflect the early solar nebula ratios, and those after the Big Bang. There is little deuterium in the interior of the (Sun), since thermonuclear reactions destroy it. However, it continues to persist in the outer solar atmosphere at roughly the same concentration as in Jupiter.

The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen nucleus contains no neutrons. The isotope name is formed from the Greek deuteros meaning "second", to denote the two particles comprising the nucleus.