Redox reactions are those which contain charged species on both the reactant and the product sides. To balance these equations, one must not only balance the moles of each type of atom in the reactants and products side, but also the positive and/or negative charges on either sides.

In acidic medium, due to the presence of H⁺, there will be positively charged groups.

In basic medium, due to the presence of OH^-, there will be negatively charged groups.

Some examples,

1. [Fe(CN)₆]^4- → [Fe(CN)₆]^3- + e^- 

2. Zn _(s) + 2H⁺ _(aq) → Zn ²⁺ _(aq) +H_{2 (g)}

3. Fe²⁺ + MnO^4- + 8H⁺ → Fe³⁺ + Mn²⁺ + 4H₂O