This exercise was developed to help students predict bonding between s,p and d atomic orbitals.
A student should be able to:
- draw the s, p and d atomic orbitals correctly, including the orientation within the canonical axes
- Predict bonding between different types of atomic orbitals
- Classify a bond as either sigma, pi or delta
A model kit or access to models of the orbitals might be helpful to some students.
I handed this out as a HW assigment after completing the homo-orbital overlap (s-s, px-px, dz2-dz2, etc.) and defining the types of bonds. We also went over s-px, s-py and s-pz. Students had five days to complete the assignment outside of class.
I graded students on the completed worksheet.
Out of the 81 different boxes, there are only 19 bonding interactions possible.
I assigned three different scores to each student:
x/19 for recognizing that there was a net bonding interaction (several are duplicates)
y/19 for assigning the correct bonding type to the (sigma, pi or delta)
z for the number times that a bonding interaction was predicted, but was not present.
Additional comments were given to the student regarding their drawing of the orbitals within the axes.
I was very surprised at how hard the students found this exercise. Their orbital drawing skills were not very good at all. One of the biggest problems was that they didn't know the shapes and orientations of the d orbitals within the canonical axes (5 of the 9 students had this problem!).
Out of 11 students in the class, 9 turned it in on time. Out of the 11, one came to the office and used the orbital models.
Predicted correct bonding:
6/9 student predicted all 19 bonding interactions
Other scores were 13/19, 15/19 and 17/19
Assigned correct bonding type:
6/9 students assigned the correct bonding type
Bonding where it doesn't exist:
3/9 students had no incorrect answers
3/9 students tried to label everything as a bond, even if there was no bonding present
Overall, this was an eye opening exercise for me. For the most part, a significant portion of the students didn't have a firm understanding of the 3D orientations of the orbitals. I revised the directions on the worksheet and have posted the revised worksheet here. I will definitely use this again, but earlier in the semester (I used it about 1/2 way through) and emphasize the importance of learning the d-orbitals!