Molecular Shape

[skyeblee2F]

IF5 has a VSEPR formula of AX5E but has a square pyramidal shape. Why doesn't it have a trigonal bipyramidal shape? Wouldn't the electron densities be more spaced out this way?

[Sarah Fatkin 4I]

Hi! IF5 would not have trigonal pyramidal shape because that would mean it would be AX3E (three bonds, one lone pair).

[skyeblee2F]

sorry, I meant trigonal bipyramidal, not pyramidal

[Nicolette_Canlian_2L]

I believe its geometry comes about because of the lone pair on the iodine. If it were trigonal bipyramidal, there would not be any lone pairs on the central atom.

[Raymond Ko 1H]

The lone pair on the Iodine atom pushes the other atoms down, creating a square pyramidal structure. The structure for an AX5 molecule is trigonal bipyramidal, so removing one of the bonds and replacing it with a lone pair would result in repulsion.