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.
