Which metal will have the highest third ionization energy, magnesium or aluminum?

1 Answer
Nov 23, 2016

Answer:

On the basis of its electronic structure, clearly magnesium metal will have the highest third ionization energy.

Explanation:

Consider the electronic configurations of aluminum, and magnesium.

#Mg,# #Z=12#: #1s^(2)2s^(2)2p^(6)3s^(2)#.

#Al,# #Z=13#: #1s^(2)2s^(2)2p^(6)3s^(2)3p^1#

Because the third ionization energy involves the removal of a #2p# electron, that is more closely bound to the nuclear core, this electron should require more energy to remove. On the other hand, aluminum has 3 valence electrons, and a stable #Al^(3+)# oxidation state, from which only electrons from the third valence shell have been removed.

Now as a chemist, as a physical scientist, you should consult the data in order to establish that I am not telling pork pies. See here for a start.