Symmetry of VSEPR Structures with Lone Pairs

(Polar molecules, Non-polar molecules, etc.)

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Isa Samad 1L
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Symmetry of VSEPR Structures with Lone Pairs

Postby Isa Samad 1L » Sat Nov 25, 2017 11:17 pm

While I was doing homework problems, I noticed that XeF4 had the molecular geometry of square planar but was considered non-polar since its lone pairs are opposite of one another and thus, cancel each other out, resulting in a overall non-polar molecule. Are there any other examples of VSEPR structures (besides square planar) with lone pairs that are non-polar?

Nishma Chakraborty 1J
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Re: Symmetry of VSEPR Structures with Lone Pairs

Postby Nishma Chakraborty 1J » Sun Nov 26, 2017 5:43 pm

Hey!

Yes, I think that there are some more cases where there can be VSEPR structures with lone pairs that are non-polar. For example, a shape with five electron densities (trigonal bipyramidal) is considered linear when it has 3 lone pairs. However, these lone pairs lie on the equatorial axis, so they essentially cancel out each other. Because of this symmetry, the molecule is non-polar.

This applies to other VSEPR structures as well. For instance, a shape with six electron densities (octahedral) and 4 lone pairs of electrons is considered linear, with the lone pairs characteristically on the equatorial axis canceling out each other. This makes the molecule non-polar. The symmetry of the lone pairs of electrons helps determine whether a molecule will be polar or not.

Hope this helps!


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