How can you tell when bond angles are going to be "slightly less than" 109.5/120, etc.??
Re: Bond Angles
Posted: Mon Nov 26, 2018 5:29 pm
When there is a lone pair present, its electron density will always cause a repulsion of the other densities, causing slightly smaller bond angles. A trigonal pyramidal molecule is essentially a tetrahedral (109.5º) where one of the bonds is replaced with a lone pair. This lone pair experiences repulsion with the other bonds, resulting in angles slightly less than 109.5º, 107º to be more exact.