Al has higher 2nd ionisation energy — why?

[JessicaHelena]

Homework Statement

The question's in the screenshot attached.

Homework Equations

The Attempt at a Solution

I don't know why (B) would be right. I feel like since for Mg's second ionisation energy, it is going from Na to Ne, and Ne is another energy level, Mg's 2nd ionisation energy should be higher than that of Al, but the answer says otherwise. Why? Please help me understand!

 

[RPinPA]

I don't know what you mean by "it is going from Na to Ne". It's not Na, it's not Ne. It still has the same number of protons in the nucleus, and that makes it still Mg. An unbalanced Mg ion with more protons than electrons.

The explanation is given in the question. The outer electrons for both Mg and Al are in shell #3. Mg has two outer electrons, Al has three. With a second ionization energy in both cases it is level 3 electrons you are removing. Mg has 12 protons in its nucleus and Al has 13, so Al has a stronger force holding the electrons. It takes more energy to peel them away.

Ne is another energy level,

I sort of get what you're trying to say, but it's not true. The second electron you're removing is not in another level, it's the second electron of level 3. Same level as the first one you removed. And same level as the second electron of Al.