Question

What is meant by the atomicity molecule?

Answer 1

Hint:
Number of atoms attached to each other in a molecule in an elemental state. Valency can also be predicted according to the atomicity of any element.

Complete answer:
The number of atoms present in a single molecule is termed as its atomicity. It can be classified as monatomic, diatomic, triatomic, tetra-atomic. For example, we can see that some molecules of many elements are composed of only one atom of that element. They are termed as monatomic. For example, inert gas like Helium (He), Neon (Ne), Argon (Ar). So, their atomicity is one. Again, sometimes the molecules of many elements are made up of two atoms of that element. For example, oxygen can never exist as an independent element and thus exist as an ${O_2}$ molecule known as a diatomic molecule. So, its atomicity is 2. Sometimes, molecules of many elements are composed of three atoms of that element. They are termed as triatomic. For example, ${O_3},C{O_2}$ . So, their atomicity is 3. Again, molecules of many elements are composed of four atoms of that element. They are termed as tetra atomic. For example, ${P_4},S{O_3}$ .
So, their atomicity is 4.

Note: There is a simple way to determine the atomicity of any element. It can be defined as the ratio of molecular mass to the atomic mass. For example, the molecular mass of the oxygen molecule is $32\left( { = 2 \times 16} \right)$ , while the atomic mass is 16. If we divide these two terms, we will get atomicity as $2\left( { = 32/16} \right)$ , which is the atomicity of the oxygen. Thus, the atomicity of an element = molecular mass/atomic mass.