Chapter 9, Problem 110E

When atoms lose more than one electron, the ionization energy to remove the second electron is always more than the ionization energy to remove the first. Similarly, the ionization energy to remove the third electron is more than the second and so on. However, the increase in ionization energy upon the removal of subsequent electrons is not necessarily uniform. For example, consider the first three ionization energies of magnesium:

First ionization energy	738 kJ/mol
Second ionization energy	1450 kJ/mol
Third ionization energy	7730 kJ/mol

The second ionization energy is roughly twice the first ionization energy, but then the third ionization energy is over five times the second. Use the electron configuration of magnesium to explain why this is so. Would you expect the same behaviour in sodium? Why or why not?