Question

What is the atomicity of ${O_3}$?

Answer 1

Hint: We can define atomicity as the total number of atoms that is found in a molecule. For example, a molecule of oxygen, which is written as ${O_2}$ contains 2 atoms of oxygen and so its atomicity is two. We can also find atomicity using the molecular mass and atomic mass of the molecule. In ancient times atomicity had the similar sense as valency.

Complete step by step answer:
We know that the total number of atoms that is present in a molecule is atomicity. Based on the atomicity, we can classify molecules as,
-Monoatomic: Molecules that contain one atom (Example: $He$, $Kr$, $Ne$)
-Diatomic: Molecules that contains two atoms (Example: ${H_2}$, ${O_2}$, ${N_2}$)
-Triatomic: Molecules that contains three atoms (Example: ${O_3}$)
-Polyatomic: Molecules that contains three or more atoms (Example: ${P_4}$, ${S_8}$)
We can calculate atomicity using the molecular mass and atomic mass of the molecule. We can write the formula as,
Atomicity=$\dfrac{{{\text{Molecular}}\,{\text{mass}}}}{{{\text{Atomic}}\,{\text{mass}}}}$
The molecular mass of ${O_3}$ is $48$.
The atomic mass of oxygen is $16$.
Let us now substitute the values of molecular mass of ozone and atomic mass of oxygen in the formula of atomicity.
We can calculate the atomicity of oxygen as,
Atomicity=$\dfrac{{{\text{Molecular}}\,{\text{mass}}}}{{{\text{Atomic}}\,{\text{mass}}}}$
Atomicity=$\dfrac{{{\text{48}}}}{{{\text{16}}}}$
Atomicity=$3$
Therefore, the atomicity of ozone is three.
Alternate way:
The total number of atoms that is present in a molecule is atomicity. We know that a molecule of ozone contains three atoms of oxygen, and therefore, its atomicity is three.


Note:
We know that all metals and some other elements like carbon do not contain a simple structure but show a large and indefinite number of atoms linked together. Their atomicity cannot be determined and in such cases atomicity considered as 1. There may be variation in atomicity for different allotropes of the same element.