Outline 3 Learning Objective

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

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Samantha Pedersen 2K
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Outline 3 Learning Objective

Postby Samantha Pedersen 2K » Mon Nov 23, 2020 4:56 pm

One of the learning objectives on Outline 3 says, "Explain why lone pairs are more likely to be found in certain locations around a central atom and
how and why they affect the bond angles in a molecule, cation, or anion."

I know Dr. Lavelle said that in a seesaw shape molecule, the lone pair will be in one of the equatorial positions because this ensures that it interacts with only two bonds at 90 degrees rather than three. I believe he also said that in a square planar molecule, lone pairs will be located in axial positions at a 180 degree angle away from each other.

Are there other VSEPR shapes where lone pairs need to be in specific positions that I'm missing?

Josh Chou 3K
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Re: Outline 3 Learning Objective

Postby Josh Chou 3K » Mon Nov 23, 2020 6:07 pm

I don't know if we went over it in class, but I think the T-shape follows the general formula AX3E2 with both lone pairs in the equatorial positions

Pranav Kadiyala 1A
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Re: Outline 3 Learning Objective

Postby Pranav Kadiyala 1A » Mon Nov 23, 2020 11:40 pm

Any molecule with a lone pair has its shape severely impacted, where its atomic geometry is totally different with and without the lone pair (bent vs linear, for example). Lone pairs are in the location they are because they minimize e- e- repulsion. If you recall, lone pair lone pair interactions are the most repulsive (therefore the most unstable), followed by lone pair - bond and lastly bond-bond. The location of the lone pairs around an atom or ion are to minimize this repulsion and therefore make the molecule as stable as possible. This goal affects the entire shape.

Subsequently, I think it would be useful to know where the lone pairs would be in any shape with lone pairs - angular, trigonal pyramidal, etc.

Hope this helps :)

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