Answer to Question #272087 in General Chemistry for Richy

Question

We know that Chromium has 5 electrons in 3d and 1 electron in 4s. Another example, Copper has 3d10 and 4s1. What knowledge of spectroscopy shows us this matter? I mean what is the reason for this matter? I know about orbitals. Our teacher says it has physical phenomena. I'm looking for that. Please explain completely. Thank you!

Answer 1

There are two main exceptions to electron configuration: chromium and copper. In these cases, a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.