In some chemical reactions, one species loses electrons by transferring them to another species. Consequently, the products have different charges than the reacting elements or ions. Losing electrons is called oxidation and gaining electrons is called reduction. Because free electrons cannot remain in a system, both reduction and oxidation must occur together. Such reactions are termed redox reactions. Just as atoms must be balanced in a chemical reaction, the charges in a redox reaction must also be balanced. Reduction and oxidation processes may be expressed separately as half reactions. Half reactions cannot occur independently, but they are useful because they show the gain or loss of electrons by each species. For the half reactions given, M and A represent neutral atoms. Identify each half reaction as showing oxidation, reduction, or as incorrectly balanced.