Oxygen

Chemical element with the atomic number 8, i.e. divalent. Highly reactive, thus a part of very many compounds. In its elementary form, a molecular gas (O₂). In small traces, also as ozone (O₃). Oxygen is the most abundant element in the earth crust and makes up for 21% of the earth atmosphere.

Also in plasma engineering, it is a major process gas and plays an important role particularly in plasma cleaning and plasma activation of plastics.