Polarity

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

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Courtney McHargue 1I
Posts: 56
Joined: Fri Sep 28, 2018 12:17 am

Polarity

Postby Courtney McHargue 1I » Sun Nov 25, 2018 11:35 am

Is a VSEPR model shape always polar if the central atom in the lewis structure has lone pairs? Or can lone pairs be symmetrical and cancel out charges to make the molecule non-polar?

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

Re: Polarity

Postby A De Castro 14B 2H » Sun Nov 25, 2018 12:06 pm

A VSEPR model shape is not always polar, even if the central atom has lone pairs. An example of a shape where lone pairs are symmetrical and cancel out each other's charges is square planar, AX4E2. This is because the lone pairs are in axial position away from each other (i.e. 180° away, on opposite sides of the central atom).
Last edited by A De Castro 14B 2H on Sun Nov 25, 2018 2:41 pm, edited 1 time in total.

Irene Zhou 1E
Posts: 73
Joined: Fri Sep 28, 2018 12:18 am

Re: Polarity

Postby Irene Zhou 1E » Sun Nov 25, 2018 12:19 pm

Just because a molecule has lone pairs does not mean that it is necessarily polar. It more depends on the where the lone pairs are and how the bonds are placed, if they cancel or not. Think of it as vectors pulling the molecule in opposite directions.

Aili Ye 4L
Posts: 58
Joined: Fri Sep 28, 2018 12:16 am

Re: Polarity

Postby Aili Ye 4L » Sun Nov 25, 2018 3:40 pm

Polarity depends on symmetry of the molecule. Sometimes lone pairs can cancel out, such as in the case of AX4E2, which is square planar. Since the lone pairs are directly opposite each other, the repulsion caused by them cancel out, and thus the atoms remain in a symmetrical position.

Kelsey Li 3B
Posts: 34
Joined: Fri Sep 28, 2018 12:26 am

Re: Polarity

Postby Kelsey Li 3B » Sun Nov 25, 2018 3:49 pm

A VSEPR model shape is not always polar. Polarity depends on the symmetry of the molecule and even if the molecule has lone pairs, it doesn't have to be polar because lone pairs can cancel out.

Anna O 2C
Posts: 98
Joined: Fri Sep 28, 2018 12:19 am

Re: Polarity

Postby Anna O 2C » Sun Nov 25, 2018 5:57 pm

Aili Ye 1I wrote:Polarity depends on symmetry of the molecule. Sometimes lone pairs can cancel out, such as in the case of AX4E2, which is square planar. Since the lone pairs are directly opposite each other, the repulsion caused by them cancel out, and thus the atoms remain in a symmetrical position.

Adding onto this, the electron clouds and their subsequent polarity can cancel out because the negativity has a direction on both sides of the molecule. Because of this, their opposing positions cancel each other out because one side of the molecule fails to be more negative than the other.

Daniel Chang 3I
Posts: 33
Joined: Fri Sep 28, 2018 12:23 am

Re: Polarity

Postby Daniel Chang 3I » Sun Nov 25, 2018 9:14 pm

It is more important to look at the VSEPR shape of the molecule to see if its polar in conjunction with the lone pair to see if its polar or not.


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