Why is it that >>>>>>>>>?

Question

10. d

The 1st ionization enery for Mg is 738 kilojoules per mole and that Al is 578 kilojoules per more ?
account for this difference

Answer 1

When predicting ionization energies follow these steps:

Are the electrons you are comparing in different energy levels?
(If "yes" then the one closest to the nucleus should have the higher energy)

Are there special cases of stability present?

-filled levels have much higher ionization energies
-filled orbitals (s2, p6) have higher ionization energies
-half-filled orbitals (s1,p3,d5) tend to have slightly higher energies

Finally, is the proton/electron ratio higher. Higher ratios give higher ionization energies.

In this case, Mg has a filled last orbital (s2) which gives it a special stability leading to the unusually higher ionization energy for Mg.

Answer 2

It has to do with the subshells. Magnesium has a full s orbital so it is reluctant to give up an electron.