1. OXIDATION NUMBERS Section 22.2

2. Assigning Oxidation Numbers  A positive or negative number assigned to an atom according to the following rules: 1. The oxidation number for a monatomic ion is equal to its ionic charge 2. The oxidation number of hydrogen is +1, except for metal hydrides, where it is -1 3. The oxidation number of oxygen is -2, except in peroxides, where it is -1 4. The oxidation number of an atom in uncombined form is 0 5. For any neutral compound, the sum of the oxidation numbers must equal 0 6. For a polyatomic ion, the sum of the oxidation numbers must equal the ionic charge of the ion

3.  What is the oxidation numbers of each kind of atom in the following compounds?  SO 2  CO 3 2-  K 2 SO 4

4. Let’s try it! 2AgNO 3(aq) + Cu (s)  Cu(NO 3 ) 2(aq) + 2Ag (s) 1. Find the oxidation number of each atom. +1 +5 -2 0 +2 +5 -2 0 2AgNO 3(aq) + Cu (s)  Cu(NO 3 ) 2(aq) + 2Ag (s) 2. Which atom is being oxidized? Copper ~ Cu (s)  Cu +2 (aq) 3. Which atom is being reduced? Silver ~ Ag + (aq)  Ag (s)