What is Reduction


According to the old (classical) concept, it is defined as the process which involves the addition of hydrogen or any other electro-positive element or radical to an element or a compound or the removal of oxygen or any other electro­negative element or radical from a compound.

For example:

Addition of Hydrogen or any other electro-positive element.

  • N2 +3H2 –> 2NH3

In this reaction H2 is added to N2 and is reduced to NH3.

  • HgCl2 + Hg –> Hg2Cl2

Here, Hg (mercury), an electro-positive element, is added to HgCl2 and is thus reduced to Hg2Cl2.


Removal of oxygen or any other electro-negative element or radical.

  • 2HgO –> 2Hg +O2

Here, HgO looses O2 and is reduced to Hg.

  • 2FeCl3 + H2 –> 2FeCl2 + 2HCI

Here, FeCl3 looses Cl2, an electro-negative element and is reduced to FeCl2.


According to the electronic concept, reduction is a process which involves gain of electron by an atom. Due to gaining of electron there will be an increase of negative charge or decrease in positive charge.


  • 2Na + Cl2 –> 2NaCl

In the above reaction chlorine gains one electron and is thus reduced.