Question

What do you understand by the term oxidation number.

Answer 1

Oxidation number :-

Oxidation numbers are known as hypothetical numbers connected with particular atom or ion which is to be present in a substance by using a set of rules. It is also known as oxidation state. 

Oxidation numbers  can be positive
Oxidation number can be negative
Oxidation number can be zero.

 It is mandatory  to remember that oxidation numbers is not for group of atom or ion ,Oxidation number are always reported for one particular atom or ion.

Example :-

Take an example of Fe³⁺ .

Fe³⁺ → +3 (oxidation number) . this means that it can assign 3 electron in formation of chemical bond.

Take an Example of O²⁻ .

O²⁻ → -2 ( oxidation number) . This means here , it can donate 2 electrons in formation of chemical bond.

Take an example of Fe₂O₃ .

Fe₂O₃ → Oxidation number for Fe₂ is +6 ,While oxidation number of O₃ is -6.
So the sum of oxidation number is zero , hence the substance become electronically neutral in formation of chemical bond.

There are some more possible rules -

(i) In the element form the oxidation number of an atom is tends to be zero.
(ii) Oxidation number of Florine is always = -1
(iii) Oxidation number of any mono-atomic ion = charge of that mono-atomic ion. Like , S²⁻ = -2 , O²⁻ = -2 etc.
 

Hope it Helps :-)

Answer 2

The amount of charge present in an atom is called as oxidation number