Oxidation Numbers

Rust is the result of oxidation.

Oxidation and reduction are opposites of each other. Oxidation involves an increase in the oxidation number of an atom. Reduction occurs when the oxidation number of an atom decreases. These two processes go together. Whenever a substance loses electrons, another substances gains electrons. You will find that oxidation-reduction reactions are called redox reactions. Remembering what is being oxidized and what is being reduced in these reactions is tricky. Why is it tricky? Ions are not always directly involved in the reactions. In this topic, you will learn how to assign oxidation numbers. These oxidation numbers are vital in the identification and analysis of redox reactions.

Essential Questions

• How are the oxidation number rules used to determine the oxidation number of an atom of any element in a pure substance?
• How are oxidation numbers calculated?