H2.Hydrogen is a chemical element with symbol H & atomic number 1.00794 u (1. With an average atomic weight of 1.007825 u for hydrogen-1), hydrogen is the lightest element & its monatomic form (H1) is the most abundant chemical substance, constituting roughly 75% of the Universes baryonic mass. Naturally occurring atomic hydrogen is rare on Earth as hydrogen readily forms covalent compounds with most elements & is present in the water molecule & in most organic compounds.
answered Sep 06, 2023 at 21:44