The second question is, how do I determine the bond order? I know the formula:
BO = (bonding electrons - antibonding electrons)/2
I found a MO diagram for the triiode, there are two bonding electrons and two non-bonding electrons which yields a bond order of 1. But for the pentaiodide and the heptaiodide, I have no reference MO diagram, hence I do not know how to determine the bond order. Can you please give some hints?