3.F.15

[Michael_Kelly_2L]

Why does AsF3 have a higher boiling point than AsF5? I drew out the Lewis structues and I noticed that As has a lone pair in AsF3. Does this contribute to the strength of its intermolecular forces?

[Gretchen_Fan_3C]

It is because AsF5 only has London Dispersion Forces whereas AsF3 has LDF along with dipole-dipole which are stronger intermolecular forces. This leads to higher boiling point. Hope this makes sense!

[Michael_Kelly_2L]

Could you explain how you know that AsF3 has dipole-dipole interactions but AsF5 does not?

[Jasmin 2C]

AsF3 has lone pairs which cause the molecule to be polar. As a result, this causes the molecule to have a dipole-dipole interaction. Polar molecules usually possess dipoles.