lone pairs in trigonal bipyramidal shape

(Polar molecules, Non-polar molecules, etc.)

Moderators: Chem_Mod, Chem_Admin

Lindsay H 2B
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

lone pairs in trigonal bipyramidal shape

Postby Lindsay H 2B » Mon Nov 13, 2017 4:29 pm

Why is it that when there are five regions of e- density but 2 of them are lone pairs on the central atom (such as ICl3 in ex 4.9a) both lone pairs are in the equatorial positions rather than the axial positions? I thought that the point was to keep lone pairs as far apart as possible, and if 2 lone pairs took the 2 axial positions, they would be farther away from each other than in 2 of the equatorial positions.

Cooper1C
Posts: 50
Joined: Fri Sep 29, 2017 7:07 am

Re: lone pairs in trigonal bipyramidal shape

Postby Cooper1C » Mon Nov 13, 2017 4:45 pm

See figure 4.5 in the textbook (page 115): "If the lone pairs had taken the axial positions, they would have been at 90 degree angles from the equatorial positions, resulting in greater repulsion."

Elizabeth Ignacio 1C
Posts: 39
Joined: Fri Sep 29, 2017 7:07 am

Re: lone pairs in trigonal bipyramidal shape

Postby Elizabeth Ignacio 1C » Mon Nov 13, 2017 7:09 pm

If the lone pair is axial, it interacts with three atoms instead of the (only) two atoms it would interact with as an equatorial. As an equatorial lone pair, it would just interact with the axial atoms. The molecule prefers this because it takes less energy.


Return to “Determining Molecular Shape (VSEPR)”

Who is online

Users browsing this forum: No registered users and 3 guests