Oxidation can be defined as the loss of electrons by an atom or ion, while Reduction can be called as the gain of electrons by an atom or ion. Neither reduction nor oxidation occurs alone. Both of them occur simultaneously. Since both these reactions must occur at the same time they are often termed as "redox reactions".
The oxidation or reduction portion of a redox reaction, including the electrons gained or lost can be determined by means of a Half-Reaction:
Fe3+(aq.) + 3e- → Fe(s)
Fe(s) → Fe3+(aq.) + 3e-
The substance that causes the oxidation of a metal is called the oxidizing agent. Or in other words, the Oxidizing agent is the substance being reduced. The substance that causes the reduction of the metal is called the reducing agent. Or in other words reducing agent gets oxidized (undergoing oxidation).
Redox reactions are mainly of two types:
• Inter Molecular Redox Reactions
• Intra Molecular Redox Reactions
It is very important to master these concepts at early stage as this forms the basis of your preparation for IIT JEE, AIEEE, DCE, EAMCET and other engineering entrance examinations.