1. Redox Reactions Nugent-Regents Chem

2. Oxidation Numbers: Rule 1: All pure elements are assigned the oxidation number of zero. Rule 1: All pure elements are assigned the oxidation number of zero. Rule 2: All monatomic (single element) ions are assigned oxidation numbers equal to their charges. Rule 2: All monatomic (single element) ions are assigned oxidation numbers equal to their charges. Rule 3: Certain elements usually possess a fixed oxidation number in compounds. Rule 3: Certain elements usually possess a fixed oxidation number in compounds. The oxidation number of O in most compounds is -2. The oxidation number of O in most compounds is -2. The oxidation number of halogens in many, but not all, The oxidation number of halogens in many, but not all, binary compounds is -1 binary compounds is -1 The oxidation numbers of alkali metals (Group I) and The oxidation numbers of alkali metals (Group I) and alkaline earth metals (Group II) are +1 and +2, respectively. alkaline earth metals (Group II) are +1 and +2, respectively. Rule 4: The sum of all oxidation numbers in a compound equals zero, and the sum of oxidation numbers in a polyatomic ion equals the ion’s charge. Rule 4: The sum of all oxidation numbers in a compound equals zero, and the sum of oxidation numbers in a polyatomic ion equals the ion’s charge.

3. Oxidation Numbers Practice: All alone= 0: Pb = Pb 0, O 2 = O 2 0 All alone= 0: Pb = Pb 0, O 2 = O 2 0 Given charge, Take Charge: Al +3 = +3 Given charge, Take Charge: Al +3 = +3 Unless noted, sum charge =0 for ionic Unless noted, sum charge =0 for ionic AlCl 3 = Al +3 and Cl -1 AlCl 3 = Al +3 and Cl -1

4. Transition Metals Assign the non-metal, the one that carries a negative charge, its usual anion charge. (O = -2, Br = -1, etc.) Assign the non-metal, the one that carries a negative charge, its usual anion charge. (O = -2, Br = -1, etc.) Set the net charge of the compound to equal zero. Set the net charge of the compound to equal zero. Calculate the oxidation number needed to balance the total charge. Calculate the oxidation number needed to balance the total charge. Example #2: What is the oxidation number of Cu in Cu 3 N 2 ? Example #2: What is the oxidation number of Cu in Cu 3 N 2 ? The oxidation number of N is -3. The oxidation number of N is -3. There are 2 N atoms: (2)(-3) = -6 There are 2 N atoms: (2)(-3) = -6 The net charge is 0. The net charge is 0. There are 3 Cu atoms: (3)(?) = +6 There are 3 Cu atoms: (3)(?) = +6 Therefore, the oxidation state of Cu is +2. Therefore, the oxidation state of Cu is +2.

5. Redox Redox Reactions: Transfer of electrons Redox Reactions: Transfer of electrons Reduction: Gain of Electrons Reduction: Gain of Electrons Oxidation: Loss of Electrons Oxidation: Loss of Electrons LEO the Lion says GER LEO the Lion says GER OIL RIG OIL RIG Law of Conservation of Mass and Charge! Law of Conservation of Mass and Charge!

6. Redox Animations Zn o + Cu +2  Zn o + Cu +2  Zn o + Cu +2  Zn o + Cu +2  Mg o + Cu +2  Mg o + Cu +2  Mg o + Cu +2  Mg o + Cu +2 

7. Assign ox #’s and balance CH 4 + O 2  CO 2 + H 2 O ox:red: Mg + CoBr 3  MgBr 2 + Co ox:red:

8. Self Check Quiz 1 Quiz 1 Quiz 1 Quiz 1 Self Check 2 Self Check 2 Self Check 2 Self Check 2 Self Check 3 Self Check 3 Self Check 3 Self Check 3