Reduction
Oxidant + e– ⟶ Product
(Electrons gained; oxidation number decreases)
Oxidation
Reductant ⟶ Product + e–
(Electrons lost; oxidation number increases)
The two parts of a redox reaction
A bonfire. Combustion consists of redox reactions involving
free radicals.
Redox (shorthand for reduction/oxidation) describes all chemical reactions in which atoms have an increase or decrease in oxidation number (oxidation state).
An oxidation number is a number assigned to an element in chemical combination that represents the number of electrons lost (or gained, if the number is negative), by an atom of that element in the compound.