(Polar molecules, Non-polar molecules, etc.)
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The valence shell electron repulsion theory is the model by which we determine molecular shapes by determining the form of the molecule which would minimize the electrostatic repulsion. This helps us to determine shapes because our Lewis structures tell us the bonds and line pairs in a molecule but not the actual arrangement of the molecules. By looking at the location of the line pairs and bonds, we can use the VSEPR model shapes in order to determine the actual arrangement of the molecules with the least electrostatic repulsion. It also helps us with estimating bond angles and polarity.
In order to determine shape, VSEPR tells us to examine the number of regions with high electron density (double bonds, lone pairs etc.). We then place those regions of high electron density as far as physically possible in three dimensions and this dictates the shape.
Adding on, minimal electrostatic repulsion is achieved when the electron-dense regions (bonds and lone pairs) on an atom are farthest from each other. There is an approximate maximum angle between bonds that can be achieved based on how many bonds are on that atom, and that is the basis of the bond angles and geometry determined by the VSEPR model.
chari_maya 3B wrote:Why are different strength bonds treated the same when applying VSEPR?
I think it has to do with the idea that the electrons account for one region of electron density, as in the bond strength does not matter as much as how many actual regions of electron density a molecule has.
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