Lone Pairs on Axial vs. Equatorial Positions

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

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Karishma_1G
Posts: 67
Joined: Fri Sep 28, 2018 12:18 am

Lone Pairs on Axial vs. Equatorial Positions

Postby Karishma_1G » Wed Nov 21, 2018 6:39 pm

The textbook on page 110 (7th edition) says that for an AX3E2 molecule, the lone pairs occupy two of the three equatorial positions where as the lone pairs for an AX4E2 occupy the two axial positions. Why wouldn't the two lone pairs on AX3E2 occupy the two axial positions like the AX4E2 molecule since 180 degrees is greater than 120 degrees?

Shubham Rai 2C
Posts: 64
Joined: Fri Sep 28, 2018 12:27 am

Re: Lone Pairs on Axial vs. Equatorial Positions

Postby Shubham Rai 2C » Wed Nov 21, 2018 10:24 pm

I think Dr. Lavelle said that this happens as the molecule wants to be in a state where the lone pairs are not in 90 degrees from the least number of bonds. So if the lone pairs occupy the axial position, they will be 90 degrees to 3 bonds while if they don't then it would be only 2 bonds.

Mallory_Podosin_1H
Posts: 31
Joined: Fri Sep 28, 2018 12:15 am

Re: Lone Pairs on Axial vs. Equatorial Positions

Postby Mallory_Podosin_1H » Fri Nov 23, 2018 12:21 pm

They don't occupy the axial positions because the lone pairs want to repel the atoms more than the 90 degrees that set-up would allow. By putting the lone pairs on two of the three equatorial positions, the lone pairs can repel the atoms more effectively and substantially.


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