C/P AAMC FL 3 - Q15

[mmchick]

Hello all -

Just a chemistry question I'd like some help with from the AAMC FL 3 test. I tried googling it, but it is such a specific scenario I can't seem to find the right explanation I'm looking for.

For how I've always understood it, I thought Group 12 elements preferred half-filled d subshells so that they could pair up vs a full-filled d subshell with single electrons. Or would a half-filled orientation be of higher energy?

Thanks!

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[Altius Premier Tutor]

Hi @mmchick, I am a current Altius tutor who just took the MCAT last June. With the answer choice you picked, you wouldn't have enough electrons to fulfill the number of valence electrons Zn has. The 3d energy level can hold 10 electrons total. If it was half filled, you have 5 from the 3d energy level and the 2 from the filled 4s energy level which would only give you 7 valence electrons which would be the number of valence electrons for Manganese. With Group 12 elements, there is no way you could have half-filled d subshells as those would have to be filled to have the right number of valence electrons. It is true that half-filled d orbitals and filled d orbitals have increased stability which is why Chromium has the electron configuration of [Ar] 3d5 4s1 (instead of 4s2 3d4) and Copper has the electron configuration of [Ar] 3d10 4s1 (instead of 4s2 3d9). Hope this helps and feel free to private message if you need further clarification!