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

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

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

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

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

End of Section 19-1

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

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

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