Polarity

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Emilie_Paltrinieri_1K
Posts: 50
Joined: Wed Sep 30, 2020 10:07 pm

Polarity

Postby Emilie_Paltrinieri_1K » Sun Nov 29, 2020 12:28 pm

Is a molecule that has a lone pair polar?

Ashley Ko 3I
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Joined: Wed Sep 30, 2020 9:54 pm

Re: Polarity

Postby Ashley Ko 3I » Sun Nov 29, 2020 12:51 pm

Hi! If a molecule has lone pairs, this does not always mean it is polar. For instance, a molecule with lone pairs is only polar if the lone pairs cause the atoms surrounding the central atom to become asymmetrically arranged. As a result, the dipole moments would not cancel out. However, if you are referring to molecules that have 1 lone pair, I believe most of these molecules would be polar (molecular shapes with one lone pair tend to be polar). Hope this helps!

Jayasree Peri 2J
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Joined: Wed Sep 30, 2020 10:03 pm

Re: Polarity

Postby Jayasree Peri 2J » Sun Nov 29, 2020 12:53 pm

I agree with Ashley! The reason having a lone pair might make a molecule polar is because the lone pair distorts the symmetry of the molecule and basically pushes the bonded atoms into a different formation.

Jiapeng Han 1C
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Re: Polarity

Postby Jiapeng Han 1C » Sun Nov 29, 2020 8:38 pm

Not necessarily so, however, lone pair could indeed disrupt the symmetry of a molecule. For a molecule with lone pairs to be non-polar, the lone pairs must cancel out. For example, consider XeF4 where the lone pairs are opposite each other(one on top and one on bottom) and the covalent bonds form a square-planar shape.

Lauren Sarigumba 1K
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Joined: Wed Sep 30, 2020 9:41 pm

Re: Polarity

Postby Lauren Sarigumba 1K » Sun Nov 29, 2020 8:42 pm

A molecule is considered polar when there is a difference in electronegativities between the atoms and when the polar bonds are NOT equally distributed in the space.

Armen_Isayan_2L
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Joined: Wed Sep 30, 2020 10:09 pm

Re: Polarity

Postby Armen_Isayan_2L » Sun Nov 29, 2020 11:32 pm

A molecule that has a lone pair is not necessarily always polar, most of the time it is, however, the arrangement of the molecule, if it is symmetrical, plays a significant role in determining its polarity.

Minh Nguyen 3A
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Joined: Wed Sep 30, 2020 9:36 pm

Re: Polarity

Postby Minh Nguyen 3A » Sun Nov 29, 2020 11:35 pm

A molecule with a lone pair does not mean that the molecule is polar. For one, the lone pairs have to be on the central atom. Assuming this is true, than the lone pairs have to impact the shape of the molecule in such a way that it becomes asymmetrical, in which case the overall molecule would be polar.

Mina Tadros 3L
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Joined: Wed Sep 30, 2020 9:38 pm

Re: Polarity

Postby Mina Tadros 3L » Sun Nov 29, 2020 11:36 pm

Lone pairs do not automatically make a molecule polar. Only if the lone pairs are located in one particular section of the molecule (thus, they're not canceling each other) will the molecule be polar.

Zach Richardson 2f
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Joined: Wed Sep 30, 2020 9:32 pm

Re: Polarity

Postby Zach Richardson 2f » Sun Nov 29, 2020 11:38 pm

Forgive me if I am wrong, but I cannot think of an example with one lone pair that is not polar. I think that if the lone pairs are opposite each other they will cancel out. If I am wrong I would appreciate it if someone corrected me.

Jaden Ji 2K
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Joined: Wed Sep 30, 2020 9:54 pm

Re: Polarity

Postby Jaden Ji 2K » Sun Nov 29, 2020 11:40 pm

A lone pair does not make a molecule polar, but usually if an atom is asymmetrical then it is polar because the dipole moments cancel each other out. On a nonpolar molecule, the dipole moments cancel each other out, which makes all the molecule neutral overall.

Jaden Ji 2K
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Joined: Wed Sep 30, 2020 9:54 pm

Re: Polarity

Postby Jaden Ji 2K » Sun Nov 29, 2020 11:44 pm

Zach Richardson 2f wrote:Forgive me if I am wrong, but I cannot think of an example with one lone pair that is not polar. I think that if the lone pairs are opposite each other they will cancel out. If I am wrong I would appreciate it if someone corrected me.

Actually that's really interesting! I found this old forum that gives an example of how multiple lone pairs can cancel each other out, but I don't see an example proving it wrong. But I think you're right.
viewtopic.php?t=845#:~:text=Answer%3A%20It%20is%20often%20true,s)%20and%20not%20be%20polar.

Gian Boco 2G
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Joined: Wed Sep 30, 2020 9:36 pm

Re: Polarity

Postby Gian Boco 2G » Sun Dec 06, 2020 10:27 pm

You can't know simply from that. You would need the other bonded atoms as well as the shape of the molecule in order to see if the dipole moments remain or cancel out.

Anthony_Sandoval_1D
Posts: 66
Joined: Wed Feb 19, 2020 12:15 am

Re: Polarity

Postby Anthony_Sandoval_1D » Sun Dec 06, 2020 10:45 pm

Lone pair does not mean a molecule is automatically polar. As others have said above, if an atom is symmetrical the usually this plays a bigger role in its polarity.

Jeffrey Fenn 1G
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Joined: Wed Sep 30, 2020 10:08 pm

Re: Polarity

Postby Jeffrey Fenn 1G » Sun Dec 06, 2020 10:50 pm

Not always, I would look at this section in the textbook, that is what really helped me.

Alex Benson
Posts: 50
Joined: Wed Sep 30, 2020 9:44 pm

Re: Polarity

Postby Alex Benson » Sun Dec 06, 2020 11:14 pm

I believe that if there is only one lone pair that makes the molecule polar, and it can be non polar if there are multiple lone pairs that balance each other out.


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