Atomic radii of Fluorine and Neon $\left(\stackrel{\circ }{\mathrm{A}}\right)$respectively are given as

Fluorine, F atomic number Z = 9 belongs to 2nd period and VIIA group. Neon, Ne has atomic no. Z =10 and it belongs to VIIIA group. Hence, for fluorine covalent radius, for Neon Vander Waal’s radius to be considered. Therefore, ${\mathrm{r}}_{\mathrm{F}}<{\mathrm{r}}_{\mathrm{Ne}}$ Because Vander Waal’s radius is greater than the covalent radius.