Particularly for the VSEPR theory, models of any kind are great. Tell the students, 'Buy a model kit.' Because it has to be something three-dimensional. They need to bring their own models in so they can do it themselves.
3D modelling software is very good. There are some Java Applets that show 3D visualisations of orbitals. You just select whichever orbital you want and you can rotate it and view it from different angles.
Use models to illustrate shapes formed by molecules. Or use balloons to illustrate bonding pairs and electron pair repulsions leading to the determination of molecular shape You can show them a tetrahedron and an octahedron etc.
For this particular topic, there are some quite nice simulations of wave functions and of orbitals and similar things on the web that can be used to visualise what orbitals look like, and what wave functions look like. They seem to like it.
When teaching electronic configuration, if it's a small class you can get each student in the class to be an electron. They can arrange themselves in different directions. It's really good if you've got steps in your classroom because you can demonstrate going up in energy. They face towards the front or the back of the room. If you simply tell them to think about parallel and antiparallel spins they come up with that themselves and it's really good when you can say, 'Yes, you came up with that yourselves.'
Use balloons to illustrate bonding pairs and electron pair repulsions leading to the determination of molecular shape For example, if you tie 6 balloons together, it automatically forms the octahedral shape. Then each time you pop one, they rearrange themselves to sequentially form the other shapes: trigonal bipyramidal, tetrahedral, trigonal planar and linear. It’s visually appealing, a concrete example and memorable for students. Also, popping the balloons wakes the students up!
In some practical demonstrations it is very simple to see which reagent is limiting, for example if one of the reactants is liquid and you add just a tiny little bit of salt to it. Just from looking at it, which one do you think will be the limiting reagent here? We have 20ml of A, and we’re going to add half a gram of B. We know though that the number of moles is the important thing, but sometimes it works just to illustrate the concept.
If you teach a course that then goes on to other things like equilibrium, electrochemistry, intermolecular forces etc, make sure that all your equations are balanced. Because it can get very lazy, especially when you’re doing organic chemistry, you don’t bother balancing anything. Coming back to that concept each time is really key for them if they’re going to understand the stoichiometry.
This concept is something that needs to be reinforced. It’s not that you taught it in this unit for three weeks, we are over it. It’s something that keeps coming back, and you can possibly reintroduce it, with not much change to your teaching. Not every single time, but every now and then remind the students, 'Remember, you still have to think about stoichiometry and limiting reagents.'
