. . "A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the elemental (baryonic) mass of the universe.In everyday life on Earth, isolated hydrogen atoms (usually called \"atomic hydrogen\" or, more precisely, \"monatomic hydrogen\") are extremely rare."@en .