Lone Pair location

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

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Goyama_2A
Posts: 107
Joined: Sat Aug 24, 2019 12:17 am

Lone Pair location

Postby Goyama_2A » Sun Nov 17, 2019 12:49 pm

Why in some molecular shapes (like square planar) are the lone pairs on opposite sides of the central atom but in other molecular shapes (like bent or t-shape) the lone pairs are next to one another? How do you determine where the lone pairs are in relation to one another about the central atom?

MinuChoi
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

Re: Lone Pair location

Postby MinuChoi » Sun Nov 17, 2019 1:04 pm

In some shapes such as bent, it is physically impossible to have lone pairs on opposite sides of the atom. Keep in mind the tetrahedral geometry of bent molecules.
For the t-shape, you'll want to look at the lone pair's angles with the other 3 bonds. In the t-shape position, the lone pairs have higher bond angles in relation to the other bonds than they would if they occupied axial positions.

Christine Honda 2I
Posts: 116
Joined: Sat Sep 14, 2019 12:17 am

Re: Lone Pair location

Postby Christine Honda 2I » Sun Nov 17, 2019 1:09 pm

In the see-saw shape the axial and equatorial positions are not chemically equivalent. If the lone pair is in the axial position, we have three LP–BP repulsions at 90°. If the lone pair is in the equatorial position, we have two 90° LP–BP repulsions at 90°. With fewer 90° LP–BP repulsions, we can predict that the structure with the lone pair of electrons in the equatorial position is more stable than the one with the lone pair in the axial position.

In square planar the lone pairs are on the opposite side in the axial positions so that all LP–BP repulsions are the same.

DHavo_1E
Posts: 118
Joined: Sat Aug 17, 2019 12:17 am

Re: Lone Pair location

Postby DHavo_1E » Sun Nov 17, 2019 7:24 pm

Hello,

In that case, would H2O have a lone pair next to each other, or on opposite ends and why? Thank you!


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