Symmetry and Polarity

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

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Princess Jereza 3C
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Symmetry and Polarity

Postby Princess Jereza 3C » Fri Nov 15, 2019 12:12 am

Does the symmetry of a molecule, from the lewis structure, also help determine the polarity of a molecule? thanks

Ronak Naik
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Re: Symmetry and Polarity

Postby Ronak Naik » Fri Nov 15, 2019 2:25 am

You have to be careful because Lewis structures are not meant to be drawn to an accurate representation of the shape of a molecule. Although a Lewis structure may be drawn as symmetrical, we must first consider the VSEPR shape first. If we were to use the shape and symmetry of the VSEPR structure, then we are able to determine the polarity using the shape and symmetry.

Fatemah Yacoub 1F
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Re: Symmetry and Polarity

Postby Fatemah Yacoub 1F » Fri Nov 15, 2019 9:11 am

Sometimes symmetry alludes to polarity but since most of the time the lewis structure isn't the actual representation you have to base it off of the VSEPR model. A symmetric Lewis structure does not automatically mean the molecule is non polar because the VSEPR model is the actual shape of the molecule. You should base the polarity off of the VSEPR model.

Alexa Mugol 3I
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Re: Symmetry and Polarity

Postby Alexa Mugol 3I » Fri Nov 15, 2019 10:55 pm

Not really. Although asymmetrical Lewis structures are usually polar, there are many symmetrical Lewis structures that are polar too. Take water for example. It is symmetrical in its Lewis structure and its electron geometry, but it's still polar because the dipoles don't cancel out. Best to just draw the VSEPR model and determine the overall dipole moment.

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Re: Symmetry and Polarity

Postby madijohnson_4A » Fri Nov 15, 2019 11:33 pm

The Lewis structure won't show you the polarity, but it is helpful in determining the VSEPR model shape of the molecule which will then help determine polarity. If the VSEPR shape allows for dipole moments to cancel and the overall dipole moment to be zero, then the molecule will be nonpolar.

Maya Gollamudi 1G
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Re: Symmetry and Polarity

Postby Maya Gollamudi 1G » Sat Nov 16, 2019 11:29 am

The 2D representation of the Lewis structure may not accurately represent the molecule's shape. Symmetry can be determined after determining the molecule's VSEPR shape.

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Re: Symmetry and Polarity

Postby RRahimtoola1I » Sat Nov 16, 2019 2:35 pm

Are the molecules that are considered polar the ones with no lone electron pairs? So only linear, tetrahedral, trigonal planar, etc.?

Hannah Romano 4D
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Re: Symmetry and Polarity

Postby Hannah Romano 4D » Sat Nov 16, 2019 2:39 pm

Lewis structures can be deceiving of the actual molecular shape. It is best to use the VSEPR model to se the symmetry of the molecular shape. Then the dipole moments of polar bonds can create partially charged vectors. If, when considering the molecular symmetry and charge of each bond, the vectors cancel out, the molecule is nonpolar. If the vectors do no cancel out, the molecule is polar.

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Re: Symmetry and Polarity

Postby EthanPham_1G » Sat Nov 16, 2019 4:21 pm

The symmetry of a Lewis Structure can be an indicator of polarity. For example, CCl4 has a carbon atom surrounded by four chlorine atoms of equal electronegativity. Because it is a symmetrical molecule, the dipole moments of the four chlorines cancel and it is a nonpolar molecule. This would not be the case if one of the chlorines was instead a different atom with a different electronegativity, like hydrogen, then it would be polar. However, it is probably best to draw a VSEPR shape to determine polarity instead of relying only on Lewis structures.

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Re: Symmetry and Polarity

Postby HuyHa_2H » Sat Nov 16, 2019 4:59 pm

Symmetry shouldn't really be what you're looking for to determine polarity but rather use the VSEPR models instead because VSEPR models are the actual representation and Lewis structures are just inaccurate base models.

Jingyao Chen 4H
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Re: Symmetry and Polarity

Postby Jingyao Chen 4H » Sat Nov 16, 2019 5:01 pm

Symmetry in the Lewis dot structure could indicate that it’s also symmetric when it is in 3D, but I would recommend just draw out the 3-dimensional figure and determine polarity based off of that.

Joseph Saba
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Re: Symmetry and Polarity

Postby Joseph Saba » Sat Nov 16, 2019 5:04 pm

Always look at the bonds to see if they are polar first, then look at symmetry.

Anvi Brahmbhatt 4A
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Re: Symmetry and Polarity

Postby Anvi Brahmbhatt 4A » Sat Nov 16, 2019 7:40 pm

Drawing the VSEPR models and determining polarity based off of them will give a more accurate answer than determining off of Lewis structures.

Sofia Q
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Re: Symmetry and Polarity

Postby Sofia Q » Sat Nov 16, 2019 9:04 pm

Lewis structures should be mainly used to determine the shape in VSPER, and from that shape you can determine polarity more accurately.

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