Trigonal Bipyramidal

[205192823]

In the text book it said that if the shape was trigonal bipyramidal it should have 5 bonding pairs and no lone pairs but for example 2E.3 toolbox question in the text book mentions that SF4 is trigonal bipyramidal even though it had a lone pair because it has 5 regions of electron density. So does it only consider areas of e- density when determining arrangement and considers the actual bonds when determining shape?

[Brian Tangsombatvisit 1C]

Yep, electron arrangement is only determined using the # of regions of electron density, while the molecule's shape is determined using the actual number of lone pairs and bond pairs. This means that molecules with different shapes (and different formulas, ex: AX4E for SF4) can have the same electron arrangements if they have the same number of regions of electron density.

[Amir Bayat]

Yep, electron arrangement is only determined using the # of regions of electron density, while the molecule's shape is determined using the actual number of lone pairs and bond pairs. This means that molecules with different shapes (and different formulas, ex: AX4E for SF4) can have the same electron arrangements if they have the same number of regions of electron density.

The regions of electron density effect the shape, pushing atoms away from it due to the lone pair repulsion being greater than all the other repulsions.

[Pablo 1K]

E- density influences shape of molecule but is not counted in the molecular shape naming of the molecule. Only bound atoms are.

[205192823]

Thanks that helped cleared things up, also is the electron arrangement the same thing as electron geometry?

[Abby Soriano 1J]

Yes, electron arrangement can be thought of as electron geometry. Electron geometry depends on the number of regions of electron density and is supposed to help you figure out molecular geometry. Molecular geometry is where looking only at bound atoms to name molecular shape comes into play.