Oxidation-reduction

→ Oxidation

Originally chemists viewed oxidation as a class of chemical reactions in which a chemical species (e.g., atom, ion, molecule, compound) reacts with an oxygen molecule (O2) such that it combines with an atom of oxygen (O) to form an oxygen-containing product, as when hydrogen (H2 reacts with O2 to form the oxygen-containing product, H2O, namely water:

2H2 + O2 → 2H2O

In that reaction, each molecular pair of hydrogen atoms was described as having been 'oxidized' by gaining an oxygen atom, forming a chemical compound referred to as an 'oxide', in this case dihydrogen oxide.

The 'Father of Chemistry', Antoine-Laurent Lavoisier (1743-1794), in his Elements of Chemistry (1789), writes of oxidation in relation to the products formed when metals are exposed to air:

The term oxidation, or calcination, is chiefly used to signify the process by which metals exposed to a certain degree of heat are converted to oxides, by absorbing oxygen from the air.