Submitted by Jacob Lutter / Wayne State University on Tue, 08/24/2021 - 13:10
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Description

This in class activity will walk students through a more advanced example for MO diagram generation from scratch. The students will work through the symmetry, point group, character table, and MO diagram of PH2F3.

Attachment Size
16.44 KB
Learning Goals

To reinforce the comprehensive process for generating an MO diagram of a more complex example, PH2F3.

Students will:

Determine shape from VSEPR theory

Find symmetry elements

Determine the point group

Find classes for each symmetry element

Generate the appropriate character table

Determine the MO diagram in two steps, 1) the PH2 part; then combining the PH2 MO with the F3 SALCs.

Equipment needs

N/A

Related activities
Attribution, Non-Commercial, Share Alike CC BY-NC-SA
Shaun Schmidt / Washburn University

Jacob,

Thanks for submitting this LO.  I've enjoyed working through it. :)  In the process of working through it I went ahead and did a simple B3LYP at 6-31g(d) calculation on the molecule just as a second confirmation.  We have WebMO and Gaussian 16 here at Washburn that made it simple to generate some pretty pictures that confirmed most of your final results.  I will e-mail you a Word doc with those pictures and associated orbital energies.  I'll also include the Gaussian output text file.  Use these as you wish to tweak your final results.  As I'm not a computational chemist I won't guarantee their complete accuracy. :)

In terms of the LO there are a couple of fixes I think you need before publication.

1) In question 3 you ask the students to generate the character table, but don't give any guidance as to how that should be done.  You could include the full process here or reference where to find it.  Perhaps that was a previous assignment.  I would not remove the question as I agree that it is an integral part of the whole assignment.

2) In the answer key for question 3, the character for 3C2 on the A1" representation should be 1 and not -.  Simple typo.

3) In the answer key for question 5, the MO diagram for PF3H2 has a few issues due to its complexity.

3a) Please label which is PH2 and 3F.

3b) There are seven MO's in the center of the diagram which are drawn all on top of each other.  Perhaps this is ok since there energies are all so similar.

3c) The ab initio calculation I did suggested that the energy order of the MO's is different than what you have drawn.  Given that the students won't have the benefit of a computer to tell them the final estimated energies of the MO's, it may be helpful for you to comment on your expectations for the students in terms of accuracy of the final diagram.

4) For future.  If I can find the time to include this MO next time I teach my course, I will probably add the computation component.  It's beyond the scope of this LO, but would be a nice add.

Talk to ya' soon!

Cheers,

Shaun