(Named (Greek hydro, "water" + genes, "generating") by Antoine Laurent Lavoisier in reference to the generation of water from the combustion of hydrogen) A flammable, colorless, odorless, tasteless, gaseous chemical element, the lightest of the elements. Hydrogen-2 is called deuterium; hydrogen-3 is called tritium.

Symbol: H
Atomic number: 1
Atomic weight: 1.00794
Density (at 0°C with 101,325 pascals): 0.08988 g/L
Melting point: -259.14°C
Boiling point: -252.87°C
Main valence: -1, +1
Ground state electron configuration: 1s1