(Polar molecules, Non-polar molecules, etc.)
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Molecule shapes can be predicted based on Lewis dot structure using the VSEPR theory. VSEPR stands for Valence Shell Electron Pair Repulsion. It states that electron pairs in the valence shell of an atom repel each other; their molecular geometry is the result of this repulsion. Basically, we use Lewis Dot Structures to help us predict the VSEPR shape of a molecule and how other molecules interact with it.
In addition, when we are working with VSEPR theory, we might be asked to put the molecule in the form AXnEm. This helps us predict the actual 3d shape of the molecule while a lewis structure really only predicts the molecule in the 2d plane. Also, the lewis structure has things like single bonds, double bonds, and triple bonds, but VSEPR theory assumes that these bonds are already hybridized; we can see this by the principle that the number of bonds has no bearing on the shape, as regardless of the number of bonds between two atoms, there will still only be one region of electron density.
VSEPR just helps us visualize the 3-D structure of a molecule while a lewis structure is a 2-D drawing. While lewis structures are useful in showing where bonds and lone pairs are, the VSEPR model helps us understand more about how a molecule will act in an environment and what 3-D structure it will appear in.
Lewis structures are the drawings we've been doing of where the electrons and bonds are in molecules. VSEPR formulas indicate the number of atoms and lone pairs of electrons around the central atom in a molecule, written as AXnEm, where A is the central atom, X are the surrounding atoms, n is the number of surrounding atoms, E are the surrounding lone pairs, and m is the number of surrounding lone pairs.
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