Page "Hydrogen" Paragraph 1

At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H < sub > 2 </ sub >.

Naturally occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds.

Hydrogen plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules.