Molecular shape and lone pairs

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

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claudia_1h
Posts: 111
Joined: Fri Aug 09, 2019 12:16 am

Molecular shape and lone pairs

Postby claudia_1h » Sun Nov 17, 2019 9:07 pm

How is it possible for a molecule to be linear if the central atom has lone pairs? Wouldn't those electrons repel the electrons of the bonded atoms like in a trigonal pyramidal molecule? Example: AX2E3

Sidharth D 1E
Posts: 98
Joined: Sat Aug 24, 2019 12:17 am

Re: Molecular shape and lone pairs

Postby Sidharth D 1E » Sun Nov 17, 2019 9:10 pm

For the example you gave AX2E3, the lone pairs would be occupying the three planar areas of electron density and the two bonding locations would be on opposite poles, and that means the angle between them would be 180 degrees and the molecule as a whole would be linear.

ckilkeary 2G
Posts: 68
Joined: Fri Aug 09, 2019 12:16 am

Re: Molecular shape and lone pairs

Postby ckilkeary 2G » Sun Nov 17, 2019 9:16 pm

In the case of AX2E3, there are 3 lone pairs and with the strongest repulsion being lone pair-lone pair, these lone pairs are spaced out on the same plane as far away from each other as possible being at about 120 degrees away from each other. Then adding in the two bonds to the central atom, the push of the lone pairs on the bonds "evens out" because they are being equally pushed from all sides of the central atom to be pushed exactly 180 degrees from the central atom. Because of this, the shape defined by the bonds is linear.


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