Atomic radius of `""_(10)Ne` is more than that of `""_(9)F-` why?

Explanation

Fluorine forms diatomic molecule, thus atomic radius of fluroine is actually a measure of half of the internuclear distance in its molecule (i.e., half of covalent bond length of `F_(2)` molecule) but neon being an inert gas. Its atoms are incapable themselves. the only force that comes into play between the atoms is the weak van der waals force, so measure of atomic radius of Ne is equal to its van der waals radius but van der waals radius is always greater than covalent radius. thus, atomic radius of neon is largest than that of fluroine.
Furthermore, due to increase in the number of electrons in the outermost 2p-orbital of Ne, there occurs an increase in electron-electron. repulsion. so 2p-orbital of Ne suffers expansion leading to its increased atomic radius.