Dipole moments on test 4

[Alyssa Pelak 1J]

Why do PO43-, PCl5, and SF6 all not have dipole moments? And, for the future, how can you determine by looking at a lewis structure which molecules will have dipole moments?

[Ishan Saha 1L]

None of these molecules have dipole moments because the more electronegative atoms in each compound are surrounded symmetrically around the central atom. For example in PCl5, the Chlorine atoms surround the central atom equally in a trigonal bi-pyramidal fashion. Dipole movements would only occur if all the electronegative atoms are located on one side of the central atom. Those compounds you mentioned from Test 4 do not have dipole moments because the electronegative atoms surround the central atoms symmetrically and equally.

[Suhail Zaveri]

Hello,

The easy answer is that dipole moment is different from polarity. Dipole moments are based upon lone pairs, all the chemicals you mentioned lack lone pairs and this less pull on the other atoms in the structure. Only if there are lone pairs they can have a dipole moment, does that help?