Symmetry of VSEPR Structures with Lone Pairs

[Isa Samad 1L]

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]

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!