This is an in-class activity that I made to help students in my second semester general chemistry course work through some aspects of color and coordination chemistry.  The activity was performed with a demonstration of color for nickel coordination complexes (ligands: water, ethylenediamine, and ammonia). I also included equilibria and thermodynamics as those concepts apply to coordination compounds at the introductory level.  This served as a review of the concepts as well.

Students construct computer models of two transition metal complexes, solve their electronic structures, and inspect the resulting d-type molecular orbitals to identify which are non-bonding, sigma* antibonding, or pi* antibonding. After constructing a molecular orbital diagram, they determine which of the two complexes is likely to absorb light at a longer wavelength.