3.1.7 Oxidation, reduction and redox equations

Oxidation

The loss of electrons

Oxidation agents

Electrons acceptors and hence they get reduced

Reduction

The gain of electrons

Reducing agents

Electron donors and hence they get oxidised

Oxidation states

The total number of electrons an element has donated or accepted

Rules for oxidation states - uncombined elements

Uncombined elements have an oxidation state of 0

Elements only bonded to identical atoms have an oxidation state of 0

Rules for oxidation states - monoatomic ions

The oxidation state of a simple monoatomic ion is the same as its charge

Rules for oxidation states - compounds

The sum of oxidation states is equal to the overall oxidation state which is equal to the charge of the ion

The most electronegative element has a negative oxidation state (equal to its ionic charge), and other elements have more positive oxidation states

Rules for oxidation states - oxygen

Combined oxygen has an oxidation state of -2, except in peroxides, where it is -1

Rules for oxidation states - hydrogen

Combined hydrogen has an oxidation state of +1, except in metal hydrides, where it is 0

Redox reaction

A reaction where reduction and oxidation happen simultaneously

Half-equation

An ionic equation that shows oxidation or reduction — one half of a full redox equation

Full equations for redox reactions