r15h4bh - 19-12-2012 at 16:29
Hello everyone 
I just learnt about the "Wave Mechanical Model" and we learnt a little (very little, about a paragraph) about Aufbau principle, Pauli's exclusion
principle and Hund's rule. They gave the electronic configuration of the first 30 elements and I noticed that Chromium and Copper have abnormal
electronic configurations. For example,
Cu: [Ar]4s13d10
But if it were to follow what I learnt from the Aufbau principle, then it should be,
Cu: [Ar]4s23d9
So can anyone explain the reason for their abnormal electronic configurations? Please don't go into advanced Chemistry, I just started the basics, so
I'm hoping you can explain it in a way that I'll understand 
Lambda-Eyde - 19-12-2012 at 16:56
http://en.wikipedia.org/wiki/Electron_configuration#Ionizati...
smaerd - 19-12-2012 at 17:20
Of course, this has to do with Hund's rule. However, half-filled electron configurations are particularly stable so there is an energetic reason for
these abnormalities. For example we would assume Chromium to be 4s2 3d4, but the pairing energy of the S orbital is less favorable then giving both
the S as well as the D electrons half filled shells edit(forgot to include)- 4s1 3d5.Hope this makes sense.
[Edited on 20-12-2012 by smaerd]
r15h4bh - 19-12-2012 at 18:53
Thanks a lot! I saw that wiki page, but that was a bit too complex for me, so
I'm content knowing that it is somehow more stable. As I learn more, when I come back to the topic I should be able to understand the more complicated
reasoning behind it But I'd rather not confuse myself for now.
chemrox - 20-12-2012 at 15:08
That's a good wiki. Also you can get 81/2 x 11 periodic tables that have ground state configs for the elements. Three hole punched as well!
r15h4bh - 20-12-2012 at 17:29
What do you mean?
smaerd - 20-12-2012 at 17:59
He means you can print out periodic tables that fit on printer paper that include the electron configuration
r15h4bh - 21-12-2012 at 17:01
Ohhh. Sorry 
platedish29 - 29-12-2012 at 20:41
I don't check if that divergence holds too long..
Maybe thats just a tale clue on your calculators spectrum.
[Edited on 30-12-2012 by platedish29]