Term used to describe a Helium (He) Second lightest and second most abundant element (after Hydrogen) in the universe. The most abundant isotope is 4He (99.9998%), 3He is very rare. Helium comprises ~8% of the atoms (25% of the mass) of all directly observed matter in the universe. Helium is produced by hydrogen burning inside Click on Term to Read More Core of an atom, where nearly the entire mass and all positive charge is concentrated. It consists of protons and neutrons. Click on Term to Read More (4He nucleus). Alpha particles were discovered by Ernest Rutherford (1871-1937) in 1898.
Some or all content above used with permission from J. H. Wittke.