Page 362 - Chemistry eBook

More Oxidation Number Rules
3. Within a polyatomic ion, the sum of the oxidation numbers must equal the charge of the ion. Reffy, Table E (p. 2) shows the charge of the polyatomic ion. The sum of the oxidation
numbers of all of the elements in the polyatomic ion must equal this charge.
What is the oxidation number of sulfur in the sulfite ion, SO3?
1. Find sulfite’s charge on Table E: it’s -2.
2. O’s oxidation state = -2. Since there are 3 oxygen atoms (O3), multiply
-2 x 3 =6
3. The oxidation numbers of S and O must equal -2 (the charge of the ion).
-6 + X = -2
O’s oxidation number S’s oxidation number Charge of the ion X = 4. S’s oxidation state is +4.
4. All metals in Group 1 have an oxidation state of +1.
Group 1 has an oxidation
state of +1.
361 © UNIT 10: OXIDATION & REDUCTION