Electronic configuration of fluorine is 1s2 2s2 2px2 2py2 2pz1. It has only one orbital half filled and no d-orbital. The orbital cannot be unpaired. Being highly electronegative, it shows only -1 oxidation state as it saturates its valence shell by accepting one electron.
In all other halogen d-orbital are present and ns and p-orbitals, i.e. showing +3, +5 and +7 oxidation states.
