IB Chemistry R3.2.1 Oxidation and Reduction Definitions Key Definitions

Oxidation is the loss of electrons by an atom or ion. It can also refer to the gain of oxygen or the loss of hydrogen.

The oxidation state (or oxidation number) is a numerical value assigned to an atom in a compound. It is the hypothetical charge the atom would have if every bond were treated as fully ionic (bonding electrons assigned to the more electronegative atom).

An oxidizing agent is a species that accepts electrons from another species in a redox reaction. It is itself reduced in the process.

A redox reaction is a chemical reaction in which electrons are transferred from one species to another. Oxidation and reduction always occur simultaneously.

A reducing agent is a species that donates electrons to another species in a redox reaction. It is itself oxidized in the process.

Reduction is defined as the gain of electrons by an atom or ion. It can also refer to the loss of oxygen or the gain of hydrogen.