Any one knows this ?

ionization energy or ionization energy is the minimum amount of energy required to remove the valence electron i.e. the outmost orbital electron.

Why does magnesium has more ionization energy than Aluminum?

Aluminum's has one unpaired electron in it's Valence energy orbital i.e. 3p. the electrons are not paired that means it has only electron in the last orbital that's why it is written as , and Magnesium's Valence Energy Orbital i.e. 3s. the electrons are paired that means it has 2 electron that's why it is written as . It is energetically favorable for all the electrons in an orbital to be paired, which means that breaking up this pair would require more energy, that is why magnesium has more ionization energy. The Aluminum does not have paired electrons thus they are removed much easily than the paired electrons in the Magnesium.

the answer is c. nacl