Explanation

(b)
Atomic radii decrease in a period from left to right, hence, fluorine has a very less atomic radii (covalent atomic radii =0.72Å). But inert gases (like Ne) are monoatomic gases, hence, their convalent atomic radii cannot be found out. In fact, their calculated atomic radii is the van der Waals’ radii, which is found almost double to covalent radii, hence, the van der Waals’ radius of neon (Ne) is about 1.60Å.