Question

Molecular mass of nitrogen is $28$. Its atomic mass is$14$. Find the atomicity of nitrogen.

Answer 1

The molecular mass is the mass of a substance in which more than one atom is combined. Atomicity is the number of such atoms which undergo combination to form a molecule.

Complete answer:
The term atomicity is related to the number of atoms in a substance or molecule. It indicates the existence of a single element in molecular form. For example the atomicity of an oxygen molecule is two, i.e. oxygen exists as ${O_2}$.
It is considered as the natural existence of a molecule. Atomicity is the smallest or the simplest number for an element which is not broken in further small portions. Mathematically, it is the ratio of molecular mass and atomic mass of an element.
According to the basis of atomicity, molecules are classified as monatomic (e.g. Helium($He$), Argon($Ar$)), diatomic (e.g. hydrogen (${H_2}$), oxygen (${O_2}$)), triatomic (e.g. ozone (${O_3}$)) and polyatomic (e.g. phosphorous (${P_4}$) sulfur(${S_8}$)).
In this case the molecular mass of nitrogen is $28$.
The atomic mass of nitrogen given is $14$.
Thus the atomicity of nitrogen is
$atomicity = \dfrac{{molecular{\text{ }}mass{\text{ }}of{\text{ }}N}}{{atomic{\text{ }}mass{\text{ }}of{\text{ }}N}}$
$= \dfrac{{28}}{{14}} = 2$
Hence the atomicity of nitrogen is two which means one molecule of nitrogen contains two nitrogen atoms.

Note:
The atomicity of a molecule contains only a single element not a compound. For example in the molecules ${O_2}$, $C{O_2}$ and ${H_2}O$, the atomicity of oxygen in a molecule in ${O_2}$is two but not in $C{O_2}$ and ${H_2}O$. In these molecules mole concept is applicable. Thus the number of oxygen atoms present in one mole of $C{O_2}$ and ${H_2}O$ are two and one respectively. Thus atomicity is not related to the mole of a substance.