Oxidation Number

The rule of oxidation number:

1. Oxidation number for neutral substance just contains one element = 0. For example, O₂ = 0, S₈ = 0.
2. Oxidation number F = -1.
3. 3. Metal IA = +1. IIA = +2. IIIA = +3. Ag = +1. Zn = +2. Other metals have more than one oxidation number.
4. Hydrogen = +1 except in: Metal hydride = -1. NaH --> oxidation number of H = -1.
5. 5. Oxygen = -2, except in: OF₂ = +2. Peroxyde (Ex:H₂O₂) = -1. Superoxyde (Ex: KO₂)= -1/2.
6. The sum of oxidation number in a neutral compounds is zero. In H₂SO₄ compuond: H = +1 O = -2 S = +6 2H + S + 4O = 2.(+1) + (+6) + 4.(-2) = 0.
7. Simple ionic compounds have oxidation number equal to the charge on the ion. Oxidation number of Na⁺ = +1. Oxidation number of S^2- = -2.
8. The sum of oxidation number in ionic compounds is equal to the charge on the ionic compound. At NH₄⁺ oxidation number of H = +1 and N = -3. Sum = N + 4H = (-3) + 4.(+1) = +1.