ionization energy tends to increase from left to right on the periodic tablethere are two exceptions to that ruleThe two exceptions are sodium and aluminiumExplain them using quantum theory.
Sodium is not an exception, but aluminum and sulfur are Aluminum is an exception, because the 3s shell is full, and you have one 3p-electronSulfur is an exception because you have one electron in each 3p-orbital with parallel spin, and one extra with opposite spinElectrons can be stabilized through pairing energy, and due to exchange energy between electrons with the same spinThe last electron i Al has neither of these, so removing this electron is easier than to remove one of the electrons of the 3s pair in MgThe last electron in S has no other 3p electron to exchange energy withThe last electron of P is 1 of 3 parallel 3p electronsHence there is a reduction in exchange energy in going form P to SThis reduction is bigger than the pairing energy for the last electron in S.
