11 Mar 2009

How molecular orbitals change as atomic energy levels shift

Web Resources and Apps

Submitted by William F Coleman, Wellesley College

Over the years I have developed a number of interactive tools that I use in my classes. This is a tool that seems appropriate for VIPEr. Comments are always appreciated, and I am always interested in developing new tools if there is something you might find useful.

This tool allows you to look at how molecular orbitals change as the difference in electronegativities of the parent atomic orbitals increases.


NOTE ADDED OCT 2014: As Flick's site at Wellesley is not available anymore I looked in his archive website (http://www.flicksstuff.com) and found the final version of this web resource, and it is linked below.  I have left the rest of the LO unchanged for archival purposes.  --Adam Johnson, Harvey Mudd College

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Although I haven't used it in class, this looks like it will be really helpful having students internalize what happens to energy levels as you go from same energy / same atom (covalent) to very different atoms (ionic). While I can draw pictures on the board in class, watching it change over time clarifies what happens with the electrons. We'll see if my students agree next year.

This does look great!  And just in time to use in class tomorrow.

I think a great addition would be to couple this with images showing how the molecular orbital probability distributions change as one particular atomic orbital begins to dominate in the molecular orbital.   


Take a look at and see if this is of interest. http://www.wellesley.edu/Chemistry/Flick/chem341/mocovtoionic1.html. After reading your suggestion I tried to think of a reasonably honest way of showing it, and this seems to work.  The black circles represent the nuclei and the percent of A and B range from 50:50 to 99.5%B 0.5% A.



That's about two orders of magnitude better than the crappy drawings I've been putting up on the whiteboard all these years.... The addition of the sigma orbitals is fantastic (a corresponding sigma* would also be cool)!

I had the same thought as Scott earlier this evening and the latest version, with sigma bonding and antibonding orbitals is at http://www.wellesley.edu/Chemistry/Flick/chem341/mocovtoionic2.html



Now that's just pretty. Thanks a ton! I'll definitely use it!

My "energy levels" tool attempts to do something similar:


Click on the "energy levels" link.

It also calculates the Mulliken charges and Wiberg bond order and I use this to show the balance between ionic and covalent contributions to the bond.

I just stumbled on your update to this page, Adam.  I like the interactivity.

Not only do I love the finished product, but I loved watching it evolve as I followed the thread.  Thanks for creating it and responding to all of the helpful comments from everyone!

I am sad to see that the link is no longer live. I know that Flick was going to try to archive it somewhere somehow after he retired. We will update this for sure!

I found it!  http://www.flicksstuff.com/wfcmaterials/mocovtoionic2.html


I'll put this up in the original LO too

Oh thank goodness. I need this for next week's class, just tried the link, and I think I screamed just a little when the link broke. Thanks much, Adam, for tracking down the archive. Phew!

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