[rpirrie]

Hello--I have asked this question in the past, but never received a response. So, hope somebody can help me and my high school chem students.

I am aware that hypervalence used to be explained by hybridization with d orbitals. I understand that the explanation has moved away from this and towards a high electron density near the ligands. So, I tell my kids that the fluorine achieves stability, but the sulfur is happy too as its stability is increased by "revealing the full shell below the 6 valence electrons". I like this lesson because it lets them know that "octet is not king"--its really about achieving stability and that even the term hypervalency is a misnomer because it assumes that you somehow crowd extra electrons into the valent level, when its really the fluorines pulling them away.

So, here's the question--am I helping the students with this lesson? Or am I barking up the wrong tree? Would anyone like to suggest any refinements? Thanks much.

[rabolisk]

I would use molecular orbital theory to describe those. Of course, you can't gain a full level of understanding of MO theory without quantum mechanics, but I think it is a good starter.

[RandoFlyer]

When I was taught this, my professor simply said that "non-metals in period 3 and below can have more than 8 valence electrons because they are able to access empty "d" orbitals."

As rabolisk said, it might not be helpful depending on their knowledge of quantum mechanics, but I do recall that no one in my class at the time was completely thrown off.

[Vidya]

in the high school chem
we are using the term --expanded octets
F can not have expanded octet because it has only 2s and 2porbitals .Hence F can accomodate  only 8 electrons .
S can have expanded octet because it has vacant 3d orbitals in its outermost shell .
Period Number three has 3s,3p,3d orbitals in outermost shell
 

[AMEDIO]

at the high school level
explaining it on the basis of MOT will do...