My Notes
Categories
This is an in class activity that I just used to replace a lecture! After students have the basic ideas of how to perform symmetry operations and put molecules in point groups, I like to reflect on the idea of a 'mathematical group' and what that means in terms of symmetry and group theory in inorganic chemistry. This activity asks students to demonstrate the rules of groups by showing examples of how symmetry operations work within a group.Then it lets students build the C2v character table by thinking about the linear and rotational functions--and demonstrating what happens to them under each symmetry operation in the group.
| Attachment | Size |
|---|---|
| SYMMETRY CHAR TABLE BUILDING_0.docx | 49.02 KB |
- Students will use symmetry operations to demonstrate understanding of the rules of group theory.
- Students will determine the characters in a character table by demonstrating results of applying symmetry operations.
- Students will connect the linear and rotational function labels to patterns of characters in a character table.
Model kits that include tetrahedral and octahedral atom centers are helpful. Whiteboard/chalkboard is also helpful. I also had the Otterbein Symmetry resource (linked nearby) in case students needed another way to view symmetry operations.
I had already covered symmetry operations, finding point groups, and using group theory to identify polar/chiral molecules. Students have atom centers to help with visualizing three-dimensional objects and I share extra tetrahedra and octahedra as needed.
I gave students the "ground rules" for demonstrating symmetry operations using my example molecule, CH2Cl2. I walked them through the first item on page one by writing on the board. Students then continued with the rest of the group theory rules on page 1 while I consulted with student groups (most worked in pairs/trios) to make sure they understood relevant ideas and procedures.
We had mentioned character tables briefly and the idea that there is a lot of information packed into them. I gave the first example on page 2; the C2 operation. Students then continued their analysis with linear functions.
I tend to refer to "sense of direction" rather than vectors. That's just the language I use--feel free to remove that term in favor of vector or your own expression.
Rotational functions seem to be more difficult to visualize. I often resort to spinning around and asking a student to spin as my mirror image. This often helps them understand the idea of sense of rotation and changing the sense of rotation.
My sense is that using this LO made for a much smoother discussion of the material.
Evaluation
I just tried this activity with my class rather than lecturing or having interactive lecture with me drawing on the board. For now, I'm just observing how my students interacted with the material.
My sense is that students "got it" better than if I'd done much of the work for them. They explored their understanding, made mistakes, explained to each other, and asked me questions. I was so pleased that I wanted to post here ASAP!