Hydrogen gas was first artificially produced via the mixing of metals with acids.
Industrial production is mainly from the steam reforming of natural gas, and less often from more energy-intensive hydrogen production methods like the electrolysis of water, or coal gasification.
Hydrogen gas is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume, or 5-95% with chlorine.
Liquid hydrogen, H2, must be cooled below hydrogen’s critical point of 33K.
Solid Hydrogen, achieved by decreasing the temperature below hydrogen’s melting point of 14.01K or (-256.14°C). The lowest density solid (0.086 g/cm3).
Deuterium, H2, is not radioactive. Tritium, H3, radioactive.
