In this activity, the provided d orbital splitting patterns need to be matched with ligand geometries. Students are provided with the d orbital splitting diagrams for 6 ligand geometries (octahedral, trigonal bipyramidal, square pyramidal, tetrahedral, square planar, and linear). A web browser is used to view an animation (developed by Flick Coleman) which allows for the visualization of the relationship between the positions of the metal d orbitals and the ligands. Given this information, students should then be able to qualitatively rank the orbitals from highest to lowest energy. Once the orbitals are ranked in terms of energy, the pattern can then be matched to the provded splitting diagrams.
After completing this in-class activity, students should be able to:
- visualize the positions of the ligands relative to the metal's d orbitals;
- determine the energies of the orbitals based upon electron repulsion relative to the barycenter;
- qualitatively rank the d orbitals in terms of their energies for a variety of ligand fields;
- explain why the observed splitting pattern in produced for each ligand geometry.
This activity has been used both as an in-class exercise and a homework assignment, and I have found that it works much better as an in-class activity.
In the class previous to the one where the activity is completed, I work through the splitting diagram for an octahedral complex. The web-based animation is used to show the relative positions of the orbitals and the ligands. While projecting the image on a whiteboard, I illustrate the geometric arrangement of ligands using a cube and I place the metal at the center of the cube and the ligands at the center of each of the 6 faces of the cube. (This allows me to give them an idea about distance between the ligands and the orbitals.) In preparation for the next class, I ask them to think about how the ligand-orbital interactions would be different in a tetrahedral arrangement of ligands. I also remind the students to bring their laptops to the following class.
When arriving in class, I break the students up into groups of two and I ask them to work on the assignment together. They discuss the animations and can consult with other groups or me if they get stuck. The exercise is usually completed in one 50-minute lecture.