Question

What is the atomicity of sodium?

Answer 1

Atomicity is defined as the number of atoms present in the element of our concern. Since many elements generally exist as molecules, so the atomicity of the elements will not be the same for every element.

Complete step-by-step answer: Before going into the solution for the question, we should first discuss the structure of the atom to get a clear idea about atomicity.
We know that an atom consists of a nucleus which is much smaller in size than the atom. The nucleus have a radius of about ${{10}^{-15}}m$,whereas the atom has a radius of about ${{10}^{-10}}m$.There are neutrons and protons present in the nucleus of the atom because which it possess a positive as the protons are positively charged and the neutrons are charge-less species. The sum of the mass of both the species i.e. protons and neutrons are considered as the mass of the atom which is called as the atomic mass or mass number.
The electrical neutrality of the atom is maintained by the distribution of equal number of electrons with respect to the protons around the nucleus. And the presence of electrons outside the nucleus is the reason for the stability of an atom.
The atoms always have the tendency to occupy stable configuration, either completely filled configuration or partially filled configuration to gain extra stability. To be specific, the majority of atoms tends to attain the noble gas configuration and for that atom combines and forms the molecules.
Now let us discuss atomicity, the term is referred to as the number of atoms present in the element. We know that the element sodium has atomic number 11 and the element exists as Na atoms only they do not exist as molecules. So we could say that the atomicity of sodium is 1 i.e. sodium is a monatomic molecule.

Note: Na always tends to exist as $N{{a}^{+}}$ by losing one electron, as it will obtain the noble gas configuration i.e. the configuration of Na and will gain extra stability. Isotopes are compounds which will have the same atomic number but the mass number will be different, but the chemical properties of the isotopes will be the same. As the number of electrons is same and the valency also will be the same.