VSEPR theory – main concept

Understanding the underlying concept

This week as i was teaching chemical bonding to my student, i realised that she was struggling to learn VSEPR. 

I asked her why did she find it difficult and her reply was it was hard to remember all the basic shapes and bond angles. And we haven’t even got to the shapes with lone pairs!

I then proceeded to question her based on first principles. “What do you think VSEPR theory is based on?” “What is the main underlying concept how we come up with the basic shapes?” I shared a video with her which was rather useful in elucidating basic shapes which doesn’t yet involve lone pairs.

After watching the video, i asked her again what was the MAIN idea of VSEPR. 

It was to achieve minimum repulsion between electron pairs around the central atom.

From there, i extrapolated the theory to apply on novel context involving lone electrons, seven electron pairs etc. 

The point i wanted to make was, a lot of times we learn the WHAT but not the HOW or WHY. Students can definitely memorise the five basic shapes and the shapes involving lone pairs. On top of that, they can also memorise the bond angles for these shapes. But isn’t it better to understand why and how molecules arranged their electron pairs to minimize repulsion and arrived at these shapes?

An analogy would be if i told you to take the train from pasir ris to jurong, get off and take bus 30 opposite the mrt station for two stops to meet me. And the mrt service gets disrupted, you would be stranded. Why? Because you didn’t know WHERE you were going, you are just following instructions. But if you knew the name of the shopping mall where we’re meeting, you can probably just switch to a cab and still get to the destination.

So remember, ask yourself why and how, not just what is in your syllabus. You will be able to understand and retain the information much easier.

All the best!

#LearningChemistry #AskingGoodQuestions

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