Hydrogene is the lightest element ecxisting. The hydrogene atom consists only from one proton and one electron. However two isotopes exists: Deuterium has a nucleus composed by one proton plus one neutron and the Tritium nucleus contains one proton plus two netrons. In nature hydrogene only exists in form of a molecular gas H2 which however is very reactive and tends to form more stable bindings with other reagents.

Hydrogene has important applications as a process gas in low pressure plasma technology mainly because of its capacity to remove oxide layers.