I have a doubt-

Question

Why is the ionization energy required for Cl- more than F-? Can't we say that the nucleus of Cl- will be far from the valence e-, so the energy required should be less than that of F- as the nucleus of F would be nearer, so more energy would be required?

Answer 1

Hello! So your thought process is right on the problem. There is just a tidbit of info that changes your thinking to the right one where IE of F-<Cl-. Essentially, an anion's IE is pretty much the electron affinity of the neutral atom. Since chlorine has the biggest electron affinity of all elements, that means the IE is bigger than any other anion, especially florine. I hope this helps!