Question

For each of the following pairs, indicate which element has the larger first ionization energy Mg or Al. i put Mg. Repulsion of paired electrons in Mg is more significant than Al's higher effective nuclear charge. but got it wrong.

Al. Repulsion of paired electrons in Al is more significant than Mg's higher effective nuclear charge.

Mg. Repulsion of paired electrons in Mg is more significant than Al's higher effective nuclear charge.

Al. Shielding of the outermost electron of Al is more significant than Mg's higher effective nuclear charge.

Mg. The shielding and higher energy of the 3p1 valence electron of Al is more significant than the increase in the nuclear charge

those are the four choice3s

Answer 1

To be honest about it I don't like any of the answers. Mg has the higher IP because, in my opinion, the added electron in Al is at the next higher energy level (farther from the nucleus) which makes it easier to ionize aluminum's outside electron. I suppose choice 4 comes the closest to what I wrote above.