Important Final Discussion on Atomic Structure

Hi every1,

I've bursted my brains compiling all the atomic structure clarification questions not answered during turorials. That was quite abit of work so do take the time to look through them,; you may find interesting nuggets there.

Finally i want to discuss something important which I didnt touch on in tutorials very much. That is the electronic configurations of Cr and Cu.
While your notes have all the details, I want to highlight the key points to you

A) Cr is [Ar] 3d5 4s1 and not [Ar] 3d4 4s2
Why? because:
1. 4s and 3d orbitals have comparatively similar energy. So electron residing in either orbital will have not much energy difference
2. So the 4s electron is transferred to 3d orbital to minimize repulsion; 4s2 electronic configuration has paired electron whereas for 4s1 3d5 electronic configuration has no paired electrons. This is a sort of application of Hund's rule

B)Cu is [Ar] 3d10 4s1 and not [Ar] 3d9 4s2
Why? because
1. 3d10 electronic configuration has all d orbitals fully filled. resultant d subshell has a symmetrical distribution of charge which confers extra stability.

Finally. I have posted up some notes, the links are on the "links" section ---->