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Electron Configurations Stability

Posted: Thu Oct 27, 2016 12:44 am
by Dan_Jin_1K
For our periodic tables, why are some elements' electron configurations, for example, Cr: 3d5 4s1 written instead of Cr4 4s2?

Other examples
Nb: 4d4 5s1 instead of 4d3 5s2
Pt: 4f14 5d9 6s1 instead of 4f14 5d8 6s2

I understand that Pd removes the two electrons from the 5s orbital to fill up the 4d orbital, but I don't understand cases like the above mentioned one.

Thank you!

Re: Electron Configurations Stability

Posted: Thu Oct 27, 2016 9:00 am
by Anna_Kim_2E
Having a half full d5 or full d10 subshell has lower energy, therefore, where there is d4 or d9 subshell, it is better to move one electron from the 4s and fill the d subshell.