This in-class activity is to introduce the pairing of diatomic MO diagrams and photoelectron spectroscopy (PES). I will be testing this out in the fall, and will post how it goes.
I introduce the photoelectron spectrometer instrumentation immediately after completing molecular orbital diagrams of homonuclear and heteronuclear diatomic molecules. I talk through the photoelectron spectra of a hydrogen atom, a hydrogen molecule, and a helium atom, and how bands with little evidence of fine structure indicate little bonding contribution of that orbital, and that evidence of fine structure indicates more contribution to bonding. Then the students receive the handout where they practice drawing MO diagrams of N2 and CO. The PES is used as a tool to show that sp mixing occurs in N2 and CO as well as to evaluate whether orbitals are involved in bonding.
I obtained copyright permissions for both of the spectra (through June 2015 for the Miessler, Fischer, Tarr figure) on the worksheet, so no need to go find those!
Using this worksheet, a student should be able to:
construct diatomic MO diagrams
analyze photoelectron spectra and corresponding MO diagrams to determine if sp mixing occurs
Students will complete this worksheet as an in-class activity. They will have approximately 10 minutes to complete the first problem, then will pair with another student to discuss for up to two minutes before sharing/discussing their answers with the class. They will then complete the second question in the same fashion. This worksheet could also easily be used for a homework assignment.
The students should be able to draw the MO diagrams of diatomic species with and without sp mixing, then evaluate the provided photoelectron spectrum to see which MO diagram agrees with the experimental data.