Oxidation and Reduction



Oxidation is defined as the process of being oxidized or oxidizing. It refers to the loss of electrons in a reaction by an atom, an ion or a molecule. Oxidation occurs when the oxidation state of an atom, ion or the molecule rises up. The reduction is the process exactly opposite of oxidation wherein the electrons are gained and the oxidation state of a molecule, an atom or an ion goes low.




A reaction between hydrogen and fluorine gas forms hydrofluoric acid:


H2 + F2 ? 2HF


In the above reaction, fluorine is being reduced and hydrogen is oxidized. If the reaction is written in two half-reactions, you a note that oxygen is nowhere in the reaction.


H2 ? 2 H+ + 2 e


F2 + 2 e ? 2 F

Historical Definition of Oxidation Involving Oxygen:


The earlier meaning of oxidation was an addition of oxygen to a compound since oxygen gas was known as the oxidizing agent.


Since the addition of oxygen to any compound meets the principle of electron loss and a rise in the oxidation state, the oxidation definition was elongated to cover other types of chemical reactions.

Oxidation and Reduction by Oxygen Transfer:


Extraction of iron from its ore:




Since both oxidation and reduction occur side by side, the reaction is called as a redox reaction.

Oxidizing and Reducing agents:


The substance which oxidizes another substance is known as oxidizing agents. In the above chemical reaction, iron oxide is the oxidizing agent.


The reducing agent is the one that reduces something else, wherein the above chemical equation, carbon monoxide is the reducing agent.


  • Reducing agents are the one that removes oxygen from other substances.


  • Oxidizing agents are the one that adds oxygen to the other.


You can remember the modern definition for reduction and oxidation based on electrons and not hydrogen and oxygen. One of the simple methods to remember which species is reduced and which is oxidized is to apply OIL RIG which stands for Oxidation is loss and Reduction are Gain.