VSEPR labeling

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

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Brett Lieuallen 2A
Posts: 50
Joined: Wed Sep 30, 2020 9:39 pm

VSEPR labeling

Postby Brett Lieuallen 2A » Sat Nov 21, 2020 12:01 am

Can someone help describe the naming conventions of VSEPR. For example if a molecule were to have lone pairs, would the naming convention be based on the atoms or on the electron densities?

Gabby Magat 3F
Posts: 108
Joined: Wed Sep 30, 2020 10:04 pm

Re: VSEPR labeling

Postby Gabby Magat 3F » Sat Nov 21, 2020 1:11 am

I'm not sure if I'm interpreting this correctly, so I'll respond both ways:

In terms of the notation (with A's, X's, and E's), you would need to keep track of the number of atoms and lone pairs (the number of pairs, not individual electrons):
A = central atom
X = bonded atom
E = lone pair

So for example, the notation of H2O would be AX2E2 (with the 2's be subscripts just like in molecular formulas).

For the names of the molecular geometry, we would technically consider the shape based on the lone pairs and bonding pairs (because of the VSEP or "valence shell electron pair" in VSEPR). However, the atoms help visualize the shapes better so I personally find them helpful in determining the shape. Both the notation and molecular shapes work hand in hand though which is very nice (like if you know one you probably know the other... I think). I hope one of these helped!

Pranav Daggubati 3C
Posts: 112
Joined: Wed Sep 30, 2020 9:35 pm

Re: VSEPR labeling

Postby Pranav Daggubati 3C » Sat Nov 21, 2020 11:04 am

VSEPR has two different shape schemes that both have the same shapes within them. One of them uses electrons to shape, and the other uses only the atoms in the molecule. For example, H2O is tetrahedral when looking at the electron density but bent when looking at the molecule itself.

Brennan McGurrr 3C
Posts: 90
Joined: Wed Sep 30, 2020 9:47 pm

Re: VSEPR labeling

Postby Brennan McGurrr 3C » Sun Nov 22, 2020 9:56 pm

The name of the shapes in the VSEPR model are based solely off of the position of the bonded atoms in the molecule. Even though H2O was four electron density regions in a tetrahedral shape, only 2 of these regions have bonded atoms. This forms a bent or angular shape.

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