Helium is a light element comprised of two protons and two neutrons in its nucleus. Helium is chemically inert.
Atomic mass: 4.002602 g/mol
Chemical symbol: He
Helium-3 is a light isotope of Helium with only one neutron. It is one of only two known isotopes that is stable with more protons than neutrons (the other being Hydrogen). Helium-3 is being studied for potential applications as a nuclear fusion reactor fuel, and it has industrial applications, as well.