In the isoelectronic species the ionic radii of ${\mathrm{N}}^{3-},{\mathrm{O}}^{2-}\text{ and }{\mathrm{F}}^{-}$ are respectively given be

The size of an ion grows with an increase in the negative charge for isoelectronic species. the isoelectronic species the ionic radii of ${\mathrm{N}}^{3-},{\mathrm{O}}^{2-}\text{ and }{\mathrm{F}}^{-}$ are given as 171 pm, 140 pm, 136 pm respectively.