Term used to describe a heliumHelium (He) Second lightest and second most abundant element (after Hydrogen) in the universe. The most abundant isotope is He (99.9998%), He 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 nucleusCore of an atom, where nearly the entire mass and all positive charge is concentrated. It consists of protons and neutrons. (4He nucleus). Alpha particles were discovered by Ernest Rutherford (1871-1937) in 1898.
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