Helium-3
= Helium-3
{wiki=Helium-3}
Helium-3 (He-3) is a light, stable isotope of helium with two protons and one neutron in its nucleus, giving it an atomic mass of approximately three atomic mass units. It is a rare isotope compared to the more common helium-4 (He-4), which has two protons and two neutrons.