Question

Why do noble gases have comparatively large atomic sizes?

Answer 1

Hint: Noble gases are the compounds which have a fully filled orbital when we talk in the terms of electronic configuration, any of the gaseous elements such as helium, neon, argon, krypton, xenon, and radon are the examples of noble gases. And they occupy the Group $18$ of the periodic table. Earlier it was stated that they are totally unreactive due to their inert configuration but compounds of xenon, krypton, and radon are now known.



Complete step by step solution:
The factor we must know about is the types of radii exhibited by different compounds.
Covalent radius: Covalent radius refers to half of the distance of the two single bonded covalent atoms of the same chemical species or in other words of a Homonuclear $X - X$ bond.
Van Der Waals Radius: Is referred to as half of the separation between the two nuclei of two non- bonded atoms of the same chemical species at their closest possible approach.
When we compare the sizes of atomic radius we have the order:
Van Der Waals > Covalent radius.
The atomic radius has a sudden increase as we move from group seventeen that is halogens to group eighteen or an inert gas.
Now, the actual reason of that why noble gases have comparatively large atomic sizes is because in case of inert or noble gases all the orbitals are completely filled means they have ${s^2}{p^6}$ configuration and hence inter electronic repulsions are maximum resulting they do not form molecules, Moreover in case of noble gases atomic radius is determined by Van der Waals radius which is larger than the covalent radii as well as the Ionic radii.


Note: A student may think of the fact that why noble gas are still called as inert as the compounds consisting of Xenon are known to us, this is because the noble gases do not react under normal conditions and still the eighteenth group has the least number of known compounds so relatively to all the groups in the periodic table it is inert.