3. 19.1 Oxidation and Reduction
You can use rules to assign oxidation numbers.
Review assigning oxidation numbers.

6. Oxidation when valence electrons are lost.
Processes in which the atoms or ions of an element experience an increase in oxidation state are oxidation processes.
2Na (s) + Cl2 (g)  2NaCl (s)
Na  Na+ + e-
A species whose oxidation number increases is oxidized. +1

7. Reduction occurs when valence electrons are gained.
Processes in which the oxidation state of an element decreases are reduction processes.
Cl2 + 2e-  2Cl-
A species that undergoes a decrease in oxidation state is reduced. -1

8. Oxidation and reduction are paired reactions.
Why is the substance that gains electrons “reduced”?
Any chemical process in which elements undergo changes in oxidation number is an oxidation-reduction reaction, or redox reaction
The part of the reaction involving oxidation or reduction alone can be written as a half-reaction.

9. Oxidation and reduction are paired reactions.+2
Cu Cu2+ + 2e- (oxidation half-reaction) 2NO3- + 2e- + 4H+  2NO2 + H2O (reduction half-rxn) Cu + 2NO3- + 4H+  Cu2+ + 2NO2 + 2H2O (redox rxn) +5 -2 +1 +4 -2 -2 +5 +2 +4

10. Distinguishing Redox Reactions
Read from packet together

11. Redox Reactions and Covalent Bonds
Read together from packet.

12. Thinking of Oxidation States
Again….read together.

13. 19.2 Balancing Redox Equation
Equations for simple redox reaction can be balanced by inspection. Most redox equations, however, require more systematic methods.

14. Oxidation and reduction reactions are balanced separately, then added together.
The half-reaction method, or ion-electron method, for balancing redox equations consists of seven steps.
In a balanced equation, both charge and mass are conserved.

22. 19.3 Oxidizing and Reducing Agents
A reducing agent is a substance that has the potential to cause another substance to be reduced.
Reducing agents lose electrons; they attain a more positive oxidation state during an oxidation-reduction reaction. Therefore, the reducing agent is the oxidized substance.
An oxidizing agent is a substance that has the potential to cause another substance to be oxidized.
Oxidizing agents gain electrons and attain a more negative oxidation state during an oxidation-reduction reaction. The oxidizing agent is the reduced substance.

23. The more active an element is, the better it acts as an oxidizer or reducer.
The more active an element is, the greater its tendency to lose electrons and the better a reducing agent it is. The greater the distance is between two elements in the list, the more likely it is that a redox reaction will take place between them.
In your own words describe the relationship between the relative strength and their placement on the activity series.

25. Some substances can be oxidizers and reducers in the same reaction.

26. Some substances can be oxidizers and reducers in the same reaction.
A process in which a substance actgs as both an oxidizing agent and a reducing agent is called disproportionation. (You may see autooxidation used as well. Stick with disproportionation)
A substance that undergoes disproportionation is both self-oxidizing and self-reducing.

27. Some substances can be oxidizers and reducers in the same reaction.