Student volunteers from class are given the end of a rope attached to a ring. When they are directed to get as far away from each other as possible, they usually assume the correct VSEPR geometry corresponding to the number of ropes (electron groups) with minimal prompting.
This demo is usually performed when VSEPR theory is just being introduced. Allow about 15 minutes to perform this demo.
Some students have difficulty relating the basic VSEPR shapes to the fact that electron groups are actually repelling each other. This demo reinforces that correlation while also helping the visual and tactile learner apprehend the shapes.
- 6 - 2 m yellow nylon ropes with small swivel-eye bolt snaps on one end
- 2" diameter metal ring
- Solicit 4-6 student volunteers from the class. (depending on how many electron groups you wish to exhibit)
- Clip two ropes to the ring, hand the ends of the ropes to two volunteers, and tell them to get as far away from each other as they can without letting go of the rope. They will assume the linear configuration characteristic of sp hybridization (AX2).
- Clip one more rope to the ring, give the end of the rope to another vounteer, and repeat the process. They will assume the trigonal planar configuration characteristic of sp2 hybridization (AX3).
- Clip one more rope to the ring, give the end of the rope to another vounteer, and repeat the process. They will assume the tetrahedral configuration characteristic of sp3 hybridization (AX4).
- The process can be continued to exhibit sp3d (AX5) and sp3d2(AX6) configurations if so desired.