Why is the first ionization energy of aluminium lower than the first ionization energy of magnesium?
Magnesium has a full outer orbital, which is very stable and requires a lot of energy to disruptAluminium has a single electron in its outermost orbital, which is not only less stable (and hence requires less energy to remove), but the full orbital before it shields the outer electron from the attractive forces of the nucleusThe outer electron in aluminium experiences less attraction from the nucleus, and hence is more easily removed.
