## the ground state and ion exceptions

$sp, sp^{2}, sp^{3}, dsp^{3}, d^{2}sp^{3}$

Dakota_Campbell_1C
Posts: 51
Joined: Fri Sep 28, 2018 12:15 am

### the ground state and ion exceptions

For Cr and Cu what is the exception and what does it mean? from what I understand you take from the S orbital and give to the D?

Jane Burgan 1C
Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

### Re: the ground state and ion exceptions

Cr and Cu are exceptions to the ground state electron configurations rules. Normally, you would expect Cr to be [Ar]3d^4s^2, but it's actually [Ar]3d^54s^1. The reason why is because the Cr is more stable having 5 electrons in its d-orbital because then it's a half-filled subshell, compared to just 4 out of the 5 orbitals being filled, which would make it very unstable and reactive. So yes! You do take an electron from the s-orbital and transfer it to the d-orbital. The same logic applies to Cu, except its configuration will be [Ar] 3d^104s^1 because having a whole d-orbital filled is more stable.

mayra martinez 1D
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

### Re: the ground state and ion exceptions

Yea so to summarize, 3d^5 and 3d^10 have a lower Ionization energy than 4s^2 so we fill those shells first before adding electrons to the s-orbital. But for the rest of the atoms in that period you would first fill the s-orbital and then send electrons to the d-orbital.