The property/properties that show irregularity in first four...

The order of first four elements of group-17 are as follows.(\mathrm{F} < \mathrm{Cl} < \mathrm{Br} < $\mathrm{I}$) (Covalent radius)(\mathrm{Cl} > \mathrm{F} > \mathrm{Br} > $\mathrm{I}$) (Electron affinity)(\mathrm{F}^{-} < \mathrm{Cl}^{-} < \mathrm{Br}^{-} < $\mathrm{I}$^{-})(Ionic radius)(\mathrm{F} > \mathrm{Cl} > \mathrm{Br} > $\mathrm{I}$\left($\mathrm{I}$^{\text{st }}\right.) ionization energy)Electron affinity order is irregular.