What is oxidation number?and how do we get this?

Dear student,

Electrochemical reactions involve the transfer of electrons. Mass and charge are conserved when balancing these reactions, but you need to know which atoms are oxidized and which atoms are reduced during the reaction. Oxidation numbers are used to keep track of how many electrons are lost or gained by each atom.

Oxidising number is the number of electrons gained or lost by an element or compound. For example - oxidation number of oxygen is  -2 it means it can gain two electrons to complete its octate to get stability.      or   Number of electrons required by an element to complete its octate.

Example - In H₂SO₄ we have to find oxidising number of sulphur.

Let us suppose it is 'x' then (+1*2) + (x) + (4* -2)= 0

 [where 4 and 2 are the number of atoms, while +1 and -2 are oxidation numbers of hydrogen and oxygen]

By solving it, we get x = +6

This is oxidation number of sulphur.