Monday, February 1, 2010

Lectures #12 and #13, Friday, January 29th and Monday, February 1st

The topic of both of these lectures was molecular orbital theory, which is quite possibly the most difficult concept to grasp in general chemistry. I am introducing this topic now, and I will come back to it in our solar cell unit as we discuss various ways to utilize the sun's energy.

When I was lecturing on Friday, I kind of sensed a groan and a frustration in the class as everyone tried to copy down what I was saying and I do not think things were sinking in. So I put together a powerpoint of the key topics we are discussing and hopefully this can drive home the key points I want to emphasize.

Take a look at the powerpoint, which is posted on Carmen, and play around with the animations so you can visualize what is happening at the atomic level. A general theme that should come out as you look through this is that the greater the orbital overlap, the stronger the bonding interaction, and the lower in energy the bonding molecular orbitals (more stable in energy). We can analyze anti-bonding orbitals in the same way. The greater the orbital overlap, the stronger the anit-bonding interaction, the higher in energy the resulting molecular orbitals (less stable in energy).

For the exam on Wed. I will not test you on the nitty gritty details of MO theory, but I do expect you to have a solid foundation on how orbital overlap will allow you to arrange various orbital interactions in order of increasing energy (put orbitals in order from lowest to highest energy).

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