What is the predicted order of first ionization energies from highest to lowest for aluminum, phosphorus, silicon, and sulfur?

This is the answer

P > S > Si > Al

Phosphorus is in group 15 and sulfur is in group 16 so the ionization energies is a little bit lower the phosphorus.

The trend of ionization energy in the periodic table increases from left to right and from bottom to top. In the given elements, we need to refer to the periodic table for their respective positions. The elements given belong to the same period. The trend in increasing order is aluminum, silicon, phosphorus and sulfur.