Determining Polarity

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

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Siddiq 1E
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

Determining Polarity

Postby Siddiq 1E » Mon Nov 25, 2019 11:21 am

Hi I'm having trouble still picturing the shapes in 3D, which is problematic because that has a lot to do with polarity of a molecule. Does anyone have any advice on how to solve this? I know mostly you have to determine polarity on a case by case basis but is there any way to have a key like this shape is most likely polar, etc.

Vincent Leong 2B
Posts: 207
Joined: Fri Aug 09, 2019 12:15 am

Re: Determining Polarity

Postby Vincent Leong 2B » Mon Nov 25, 2019 11:49 am

There is a diagram in the textbook that tells us which geometric shapes result in nonpolar compounds as long as the surrounding atoms are the same. It's really helpful. Drawing net dipoles also helps logically reason why a certain molecule is polar or nonpolar.

Robin Cadd 1D
Posts: 113
Joined: Thu Jul 11, 2019 12:16 am

Re: Determining Polarity

Postby Robin Cadd 1D » Mon Nov 25, 2019 11:54 am

This isn't comprehensive, but may help you:
- tetrahedral, trigonal planar, octahedral: non-polar if all atoms surrounding central atom are the same; polar if different atoms surround the central atom

PranaviKolla2B
Posts: 114
Joined: Fri Aug 30, 2019 12:17 am

Re: Determining Polarity

Postby PranaviKolla2B » Mon Nov 25, 2019 12:33 pm

Many times (not always), if there are lone pairs around the central atom, the atom is polar right? What are the exceptions to this rule?

Victoria Otuya 4F
Posts: 50
Joined: Wed Sep 18, 2019 12:21 am

Re: Determining Polarity

Postby Victoria Otuya 4F » Sat Nov 30, 2019 11:16 am

So if there are lone pairs , the molecule as a whole is always polar right?

faithkim1L
Posts: 105
Joined: Fri Aug 09, 2019 12:17 am

Re: Determining Polarity

Postby faithkim1L » Sat Nov 30, 2019 12:05 pm

Drawing net dipoles helps a lot, but you need to make sure that you are not just cancelling dipoles that seem opposite each other. For example, in CHCl3, you can't cancel the dipoles of Cl that are across from each other, because the bond angle is actually 109.5 and not 90/180. Also, when there is a lone pair, it is quite likely that the molecule is polar. I've found that doing practice problems and looking up worksheets online helps you kind of gauge how to look for polarity.

Victor James 4I
Posts: 50
Joined: Wed Sep 18, 2019 12:20 am

Re: Determining Polarity

Postby Victor James 4I » Sat Nov 30, 2019 12:32 pm

I think looking up videos of the molecule shapes wo you can visualize them should help

Junxi Feng 3B
Posts: 52
Joined: Sat Sep 14, 2019 12:17 am

Re: Determining Polarity

Postby Junxi Feng 3B » Sat Nov 30, 2019 12:39 pm

First, I think you should check the textbook, there is a picture that draws out all the molecular geometry along with their polarity. Second, the polarity can be determined based on whether the surrounding atoms are the same, if they are the same, then it's likely to be non-polar; if the surrounding atoms are not the same, then it's more likely to be polar.

bellaha4F
Posts: 104
Joined: Wed Sep 18, 2019 12:20 am

Re: Determining Polarity

Postby bellaha4F » Sat Nov 30, 2019 9:45 pm

if the net dipoles all cancel out (bc of electronegativities), then it will be nonpolar (if they all cancel out)

005321227
Posts: 90
Joined: Sat Sep 07, 2019 12:15 am

Re: Determining Polarity

Postby 005321227 » Sun Dec 01, 2019 1:35 pm

memorization in this situation will help - the chart in the textbook provides the shapes along with their polarities.

Astrid Lunde 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:16 am

Re: Determining Polarity

Postby Astrid Lunde 1I » Sun Dec 01, 2019 4:23 pm

Check the net dipoles of the molecule. If you see lone pairs the molecule will always be polar.


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