Next, you break down the unbalanced reaction into the two half reactions an oxidation reaction and a reduction reaction. In the third step, you have to balance atoms in each reaction. So in the reduction reaction and the oxidation reaction and the atoms you're balancing are all the atoms other than oxygen and hydrogen. Next, you have to balance the oxygen by adding water and hydrogen by adding H plus ions. Now, this only works for acidic solutions. In basic solutions, you balance the H atoms, the hydrogen atoms by adding oh minus.