lone pair influence on shape

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Layla Manoochehri
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Joined: Fri Sep 28, 2018 12:28 am

lone pair influence on shape

Postby Layla Manoochehri » Sun Nov 18, 2018 10:24 pm

can someone explain conceptually why the presence of a lone pair will change the shape, for example from linear to bent?

Ethan Yi 1K
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Joined: Fri Sep 28, 2018 12:28 am

Re: lone pair influence on shape

Postby Ethan Yi 1K » Sun Nov 18, 2018 10:28 pm

the lone pair of electrons has a negative charge that will repel the bonding pairs that also have a negative charge, changing the shape.

405021651
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Re: lone pair influence on shape

Postby 405021651 » Sun Nov 18, 2018 10:32 pm

Lone pairs take up more space than a regular bond would take

jessicahe4Elavelle
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Re: lone pair influence on shape

Postby jessicahe4Elavelle » Sun Nov 18, 2018 10:33 pm

Electrons are negatively charged and repulse other electrons. A lone pair causes an area of high electron density so electrons repel each other more strongly than bonding pairs causing a distortion in the shape (lower angle).

Angel Chen 2k
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Joined: Fri Sep 28, 2018 12:20 am

Re: lone pair influence on shape

Postby Angel Chen 2k » Sun Nov 18, 2018 10:33 pm

The presence of lone pair around the central atom affects the bond angle. A lone pair of electrons always tries to repel the bonded electrons, when electron pairs move away from each other, the shape of the molecule is affected.

Cody Do 2F
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Joined: Fri Sep 28, 2018 12:23 am

Re: lone pair influence on shape

Postby Cody Do 2F » Sun Nov 18, 2018 10:34 pm

Hey, Layla!

For lone pairs, you have to see them as extremely repulsive in nature (they push everything, including bonds and other lone pairs, away from them). A linear molecule is flat and linear because the two atoms connected to the central atom want to be as far away from each other as possible. In order to achieve this maximum distance, the two atoms are directly opposite each other, forming a linear shape. However, if you introduce a lone pair into the equation, this all changes. This lone pair adds another region of electron density around the central atom (a linear molecule has two electron densities AKA the two bonds, this new one has three AKA the two bonds and the lone pair). Now that there are three regions of electron density, they'll all attempt to spread out around the molecule equally. If this were three bonds instead of two bonds + one lone pair, then the bond angle would be 120 degrees and the molecule would be trigonal planar. However, since we have the lone pair (and since lone pairs are extremely repulsive), the two bonds are pushed even further away from the lone pair. This is why water has a bent shape with a bond angle of 104.5 degrees—the lone pair's strong repulsion forces the two hydrogen atoms farther away from where the lone pairs are!

905096106
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Joined: Fri Oct 05, 2018 12:17 am

Re: lone pair influence on shape

Postby 905096106 » Sun Nov 18, 2018 10:51 pm

Lone pairs disrupt the shape by making the angles between molecules smaller

Simran Rai 4E
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Joined: Fri Sep 28, 2018 12:17 am

Re: lone pair influence on shape

Postby Simran Rai 4E » Sun Nov 18, 2018 11:06 pm

Also in discussion, my TA had said that paired electrons are more repulsed by lone pairs of electrons than they are by other bonded pairs of electrons. Which can also explain why they'd more readily move closer to another bonded pair in the presence of lone electrons.

MichaelMoreno2G
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Joined: Fri Sep 28, 2018 12:26 am

Re: lone pair influence on shape

Postby MichaelMoreno2G » Sun Nov 18, 2018 11:08 pm

Can someone explain the difference between bent and linear?

Simran Rai 4E
Posts: 58
Joined: Fri Sep 28, 2018 12:17 am

Re: lone pair influence on shape

Postby Simran Rai 4E » Sun Nov 18, 2018 11:17 pm

MMoreno3K wrote:Can someone explain the difference between bent and linear?


A linear shape is when the bond angles are 180 degrees exactly. This could even take place in the presence of 2 or more lone pairs depending on the amount of regions of electron density. A bent shape, however occurs when the linear shape is offset by a pair(s) of lone electrons that push the otherwise "linear" molecule's bond angles closer together due to electron repulsion.

Andrew Lam 3B
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Joined: Fri Sep 28, 2018 12:24 am

Re: lone pair influence on shape

Postby Andrew Lam 3B » Sun Nov 18, 2018 11:40 pm

Lone pairs take up more space than bonding pairs, depressing the bond angle.

Sapna Ramappa 1J
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Joined: Fri Sep 28, 2018 12:24 am

Re: lone pair influence on shape

Postby Sapna Ramappa 1J » Mon Nov 19, 2018 8:13 am

Because lone pairs have a high electron density, they take up more space. As a result, lone pairs are able to push the angles of the other bonds away from the lone pairs, thus changing the shape.

Connie Chen 3D
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Joined: Mon Jan 08, 2018 8:12 am

Re: lone pair influence on shape

Postby Connie Chen 3D » Mon Nov 19, 2018 10:00 am

Lone pairs take up a lot of space and have a ton of repulsion around them so the bonded elements get pushed away.

As for bent vs linear, linear is as it sounds like. A straight line with bond angles of 180 degrees. This only occurs when there are no lone pairs to cause repulsion. When there are lone pairs, then the molecule will be bent because the lone pairs cause the bonded elements to move away from the electrons.


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