(Polar molecules, Non-polar molecules, etc.)
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Correct me if I'm wrong, but I believe square planar is the only VSEPR shape where the molecule may contain lone pairs and still be nonpolar (if every X in AX4E2 is the same element). In any other shape, lone pairs will indicate the net dipole does not cancel and therefore the molecule is polar. Many of the VSEPR shapes with no lone pairs are able to be nonpolar, such as linear, trigonal planar, and tetrahedral with the same elements bonded to the central atom.
When you use VSEPR, the molecule will either be symmetrical or asymmetrical surrounding the central atom. You can tell if the molecule is polar or not based on if it is symmetrical. Symmetrical = non-polar, asymmetrical = polar.
The central atom has much to do with the VESPR model of molecules, and the different shapes can determine the different polarities based on the symmetry pf the central atoms and their charge distribution. For example, the molecule is nonpolar if it is symmetrical, and if the shape is asymmetrical if it is polar.
For the most part, yes, vsepr shapes are a good indicator of whether or not a molecule is polar or not. For example any VSEPR shape that has no lone pair of electrons (linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral) its structure is set up for it to be very symmetrical and for the dipole moments to cancel out. However, for VSPER shapes that include lone paired electrons, its structure does not allow the molecule to be nonpolar.
Yes, if the VSEPR model indicates that the molecule's dipole moments cancel out, then it will be a nonpolar molecule ( and same vice versa). This can be shown clearly through cis-1,2-dichloroethene and trans-1,2-dichloroethene. These molecules have the same molecular formula, but the organization of the atoms bonds is different so that only the trans-1,2-dichloroethene molecule cancels out the net dipole moments within the molecule.
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