Exceptions for Electron Configuration

[EvaLi_3J]

In the lecture on Friday 10/18, professor mentioned how there exists EXCEPTIONS that half full d subshells and full d subshells have lower energy. Does anyone remember what this is exception to?

[Nikki Razal 1L]

He said the two exceptions were for the elements copper (Cu) and chromium (Cr)

[Leyna Dang 2H]

I believe they were copper (Cu) and chromium (Cr). The configuration for copper would be [Ar]3d10 4s1 and chromium would be [Ar]3d5 4s1.

[Haley Fredricks 1B]

The norm is that the 4s orbital would fill up before the 3d orbital, so each element would have 4s^2 before 3d. However, in both Cu and Cr, the 4s orbital is not full, while the 3d orbital is partially full or completely full (3d^5 or 3d^10) for the purposes of stability. This is why they are called exceptions.

[Anokhi Patel 2B]

For the exceptions, this is since half full d5 and full d10 subshells have lower energy. As an example he compared Titanium and Vanadium to Copper and Chromium.

[805373590]

exceptions for electron configurations:
Cu-(Ar)3d^10 4s^1.
Cr-[Ar] 3d5 4s1

[pauline young 1L]

the examples he gave in class were copper and chromium, however, this does not mean those elements are the only exceptions, period 5 on the periodic table follows the same trend.