Chromium and Copper

[Joanne Reyes 1L]

Can someone explain why Chromium and Copper are the exceptions in electron configuration? Is there a reason why the electrons have to be in a different orbital?

[Kayti Luu 2B]

Normally, you would expect Cr electron configuration to be [Ar] 3d4 4s2. However because the d shell can hold up to 10 electrons, it is more stable if there are 5 electrons(half filled) rather than 4 electrons in the d shell because if it's 5 electrons then each orbital has one electron and is therefore more stable. Therefore one electron from 4s2 is removed making Cr [Ar] 3d5 4s1. Same is the case with Cu, it would be [Ar] 3d9 4s2, but again it would be more stable if the d shell is completely filled with 10 electrons, instead of 9. Therefore and electron from s is removed making Cu it [Ar] 3d10 4s1. Does that make sense? Hope it helps :)

[Sophia Galluccio]

I would also like to add that the same rules for these exceptions apply to the other elements in the same periods as Chromium and Copper, although it is not necessary to know it for the first quiz as far as I have been told.

[Joanne Reyes 1L]

I understand now, thanks for the help!

[304579397]

What other elements except chromium and copper have different electronic configurations?

[Sara Pena 1I]

All of the elements in the same group (column) as Cr and Cu have the same exception. However, Dr. Lavelle said we only have to worry about the first row of the transition metals so Cr and Cu are the only ones we have to know about for this course.

Other than that, I think most of the other exceptions are in the lower periods which aren't really present in the life sciences context.