Atomic radii of F and Ne, in $\stackrel{0}{\mathrm{A}}$ , are given by

Atomic radii decreases in a period from left to right, hence, fluorine has a very less atomic radii (covalent atomic radii = $072\stackrel{0}{\mathrm{A}}$ ). But inert gases (like Ne) are monatomic gases, hence, their covalent 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 $1.60\stackrel{0}{\mathrm{A}}$ .