NMR properties:

Magnetogyric Ratio NMR frequency Natural abundance (NA) Nuclear spin (I) Quadrupole moment (Q) Reference sample
3 He -20.378910^7 rad/sT 0.000134% 0.5
4 He
4 He

Helium is one of the so-called noble gases. Helium gas is an unreactive, colourless, and odourless monoatomic gas. Helium is available in pressurised tanks. Helium is the second most abundant element in the universe after hydrogen. α particles are doubly ionised helium atoms, He2+.

Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!).