Chapter 5, Problem 38P

The energy needed to remove one electron from a gaseous potassium atom is only about two-thirds as much as that needed to remove one electron from a gaseous calcium atom, yet nearly three times as much energy as that needed to remove one electron from ${\text{K}}^{+}$ as from ${\text{Ca}}^{+}$ . What explanation can you give for this contrast? What do you expect to be the relation between the ionization energy of ${\text{Ca}}^{+}$ and that of neutral K?