energy order of haloges?

For halogens as we move down the group the outer valence electrons are not near the nucleus,so it will not take as much energy to remove them. Therefore, the energy required to pull off the outermostelectron will not be as high for the elements at the bottom of the group since there are more energy levels. Also, the high ionization energy makes the element appear non-metallic. Iodine and astatine display metallic properties so ionization energy should decrease down the group.