Electron Configurations for Chromium and Copper

[Tamera Scott 1G]

Could someone explain again why Chromium and Copper have exceptions when it comes to writing their electron configurations? What happens to the electrons?

[amogha_koka3I]

So in these cases, I believe a completely full or half full d sub-level is more stable than a partially filled level. So an electron from the 4s orbital is 'excited' and rises to a 3d orbital. For example for copper it goes from 3d9 to 3d10 and the s orbital goes from 4s2 to 4s1. Hope that helps!

[Kelsey Warren 1I]

The Cu and Cr are more stable when their electron configurations have a full (or half full) d shell. I think we just need to know these exceptions and what they look like rather than understand exactly why they occur.