Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction. When oxidation occurs, the oxidation state of the chemical species increases. Oxidation doesn't necessarily involve oxygen! Originally, the term was used when oxygen caused electron loss in a reaction.

Why do oxidation occurs?

Oxidation occurs when an atom loses electron density to another atom. The atom with the lower electronegativity loses electron density to the atom with higher electronegativity. The Oxidizing agent has a higher electronegativity draws the electron density closer to itself. This is what causes oxidation.

Why do oxidation and reduction occur?

Because any loss of electrons by one substance must be accompanied by a gain in electrons by something else, oxidation and reduction always occur together. ... The atom that loses electrons is oxidized, and the atom that gains electrons is reduced.