Question

Complete the table given below.

Element	Atomic mass	Molecular mass	Atomicity number
Chlorine	35.5	71	-
Ozone	-	48	3
Sulphur	32	-	8
Nitrogen	14	-	2

Answer 1

Atomic mass is nothing but the molecular weight of the element in the periodic table.
Molecular mass means the sum of the molecular weight of all elements present in the molecule.
Atomicity is defined as the total number of atoms present in a molecule. For example, take an oxygen molecule (${{O}_{2}}$). Each molecule of oxygen contains two oxygen atoms. Means atomicity of oxygen is two.

Complete answer:
First we will fill the atomic mass column.
The atomic mass of oxygen is 16. The atomic mass of oxygen in ozone is also 16. The atomic mass of an element is not going to change when it is in molecular form also. Oxygen belongs to the VIth group in the periodic table.
Coming to the molecular mass column, the molecular mass of sulphur is 256. Sulphur belongs to the VIth group in the periodic table. Atomicity of Sulphur is eight.
So molecular mass = Atomicity $\times$ atomic mass
Molecular mass of Sulphur = 8 $\times$32 = 256
Molecular mass of nitrogen is 28 because nitrogen molecule (${{N}_{2}}$) contains two nitrogen atoms.
Molecular mass of nitrogen = Atomicity $\times$ atomic mass
= 2 $\times$ 14 = 28.
Coming to the atomicity column, atomicity of chlorine molecules ($C{{l}_{2}}$) is 2, meaning chlorine in nature exists in dimer form.
So, now we can fill all the above mentioned data in the given tabular form.

Element	Atomic mass	Molecular mass	Atomicity number
Chlorine	35.5	71	2
Ozone	16	48	3
Sulphur	32	256	8
Nitrogen	14	28	2

Note: There is one more method to calculate atomicity number.
Atomicity number = $\dfrac{\text{molecular mass}}{\text{atomic mass}}$
By using the above formula we can calculate atomic mass and molecular mass of all the molecules.