(Polar molecules, Non-polar molecules, etc.)
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Is there a way to calculate bond angles, or do you just have to estimate them with a range? And if you can only estimate, how would you know that the bond angle for clo2+ in 7th edit 2E 5 is slightly less than 120 degrees?
I think you should be familiar with the generic bond angles for shapes, for example, 109.5 degrees for tetrahedral, 120 degrees for trigonal planar, etc. These angles hold true unless there are lone pairs, which would reduce the bond angles slightly. In these cases, you would just have to approximate the bond angles as there is no way to calculate the bond angles. For example, CH4 (methane) has bond angle of 109.5 since it is tetrahedral but NH3 (ammonia) has a bond angle slightly less than 109.5 degrees since it has a tetrahedral electronic structure (but trigonal pyramidal shape) with a lone pair.
I believe that for certain molecular shapes you will know the angles ie trigonal planar is 120 degree angles, but for the case of molecules with lone pair electrons those you will have to give a range because there is no way to calculate the actual bond angle just by looking at VSEPR. Hope that helps!
I think for most of them you just have to memorize it for the fastest way on an exam. However it will help to realize that when there are lone pairs, that will affect the bond angles. For exme, if there are four areas of electron densities, but one of them is occupied by lone pirs, and sy the shape is trigonal pyramidal instead of tetrahedral, we can estimate the bond angle to be less than 109.5.
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