Redox Reaction ( Oxidation - Reduction reaction )

            Redox reaction is a chemical reaction, that involves electron transfer between two chemical species.
* loss of an electron is oxidized
*gain of an electron is reduced.
It is also known as oxidation - reduction reaction.

Example:

Redox reaction :
 H₂   +   F₂   →   2HF
overall reaction may be written as two half - reaction.

Oxidation reaction :

H₂   →   2H⁺   +   2e^-

Reduction reaction :

F₂   +   2e^-   →   2F^-

Now we adding the reactions together the electrons are canceled.
                 H₂   →   2H⁺   +   2e^-

F₂   +   2e^-   →   2F-

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H₂   +  F₂    →   2H⁺   +   2F^-

2H⁺   +   2F^{-  combine to give 2HF.}