2. Electron Transfer and Redox Reactions
An oxidation-reduction reaction, or redox reaction involves the transfer of electrons from one atom to another.
Section 19-1

3. Electron Transfer and Redox Reactions (cont.)
Oxidation is defined as the loss of electrons from atoms of a substance.
Na → Na+ + e–
Reduction is defined as the gain of electrons by the atoms of a substance.
Cl2 + 2e– → 2Cl–
Section 19-1

4. Oxidizing and Reducing Agents
The substance that oxidizes another substance by accepting its electrons is called an oxidizing agent.
Section 19-1

5. Oxidizing and Reducing Agents (cont.)
The substance that reduces another substance by losing its electrons is the reducing agent.
The reducing agent is the substance that is oxidized in a redox reaction.
Section 19-1

6. Oxidation Numbers in Redox Reactions
Oxidation-reduction reactions are changes in oxidation number.
Atoms that are reduced have their oxidation number decreased.
Atoms that are oxidized have their oxidation number increased.
Section 19-1

7. End of Section 19-1

8. The Oxidation-Number Method (cont.)
The total increase in oxidation numbers must equal the total decrease in oxidation numbers in the reaction.
This method is called the oxidation number method.
Section 19-2

9. Balancing Redox Equations Using Half-Reactions
In chemistry, a species is any kind of chemical unit involved in a process.
Oxidation-reduction reactions occur whenever a species that can give up electrons comes in contact with another species that can accept them.
Section 19-2

10. Balancing Redox Equations Using Half-Reactions (cont.)
A half-reaction is one of the two parts of a redox reaction—the oxidation half of the reduction half.
Section 19-2