Equitorial vs. Axial Lone Pair

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

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Ava Harvey 2B
Posts: 54
Joined: Fri Sep 29, 2017 7:04 am

Equitorial vs. Axial Lone Pair

Postby Ava Harvey 2B » Sat Nov 25, 2017 1:26 pm

Hi! I hope everyone's having a wonderful short break off from school! Can someone please explain to me when choosing to place a lone pair in the structure of a molecule, in order to determine its shape, why is it preferable to place it as an equatorial lone pair versus an axial lone pair? Or does it depend on the molecule that we're drawing? Thanks so much!

Ashin_Jose_1H
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Re: Equitorial vs. Axial Lone Pair

Postby Ashin_Jose_1H » Sat Nov 25, 2017 7:42 pm

I believe it depends on the molecule.

For example, IF4+ has an VSEPR Formula for AX4E. The shape is trigonal bipyramidal and there are two possible locations for the lone pair.

If the lone pair takes the axial position, then it would strongly repel the electron pairs in the three equatorial position.
If the lone pair takes the equatorial position, then it would strongly repel the two axial atoms.

In this case, the lowest energy is achieved when a lone pair is equatorial because it is only close to two atoms.

Kellina Tran 2I
Posts: 50
Joined: Sat Jul 22, 2017 3:00 am

Re: Equitorial vs. Axial Lone Pair

Postby Kellina Tran 2I » Sun Nov 26, 2017 1:14 am

Just to add on to the previous response, you want there to be the least amount of repulsion and energy where the lone pair is placed. I’m an equatorial position, it is only close to two atoms, versus three atoms in an axial position, so the former is the ideal arrangement.


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