Question

Oxidation number of oxygen atom in $O_3$ molecule is:
(A) 0
(B) -2
(C) +2
(D) +1

Answer 1

Hint: Oxygen being a reactive non- metal occurs in various forms, ozone is also one of the highly reactive gas made up of 3 oxygen atoms. It is both a natural and a man-made product that occurs in the earth’s upper atmosphere (stratosphere) and lower atmosphere (troposphere).

Complete step by step solution:
We have been provided with $O_3$ molecule,
As we know the molecular formula of ozone is $O_3$, that is 3 oxygen atoms,
The atomic number of oxygen is 8 and its valency is -2, as it requires 2 electrons to complete its octet.
The structure of ozone is:

Now, as we know, the oxidation number is the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. It is also known as oxidation state.
So, we need to find out the oxidation number of ozone, for that we will be using the formula:
Charge on each atom/ number of atoms
Now, we have 3 oxygens having charges 0, -1 and +1.
So, the oxidation number would be: ${\displaystyle \frac{0+(-1)+(+1)}{3}}$,
On simplifying further, we will get: ${\displaystyle \frac{0}{3}}=0$,
So, the oxidation number comes out to be 0.

Therefore, we can conclude that option (A) is correct.

Note: Ozone being highly reactive do have resonance structure but it would not change the oxidation number. Also, all the electrons of ozone are paired unlike oxygen and therefore it is diamagnetic.