Polarity

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105194078
Posts: 52
Joined: Thu Sep 19, 2019 12:17 am

Polarity

Postby 105194078 » Thu Nov 14, 2019 2:02 pm

How to know if a molecule is polar/nonpolar? Any tips?

Rabia Sumar 1C
Posts: 55
Joined: Thu Jul 11, 2019 12:15 am

Re: Polarity

Postby Rabia Sumar 1C » Thu Nov 14, 2019 2:11 pm

You can look at the difference in electronegativity to figure out if a molecule is polar or look at its shape. If a molecule is symmetric it is non-polar, i.e. CH4 would be non-polar because it's symmetrical. An example of a polar molecule is NH3, which is not symmetric.

Suraj Doshi 1L
Posts: 49
Joined: Fri Aug 02, 2019 12:15 am

Re: Polarity

Postby Suraj Doshi 1L » Thu Nov 14, 2019 2:16 pm

I believe we have to look at the electronegativity between bonds and if the difference is greater than 0.4, then the bond is polar. If the difference is less than 0.4, then the bond is nonpolar. If there are no polar bonds, then the molecule as a whole should be nonpolar.

Haley Chun 4H
Posts: 54
Joined: Sat Aug 17, 2019 12:18 am

Re: Polarity

Postby Haley Chun 4H » Thu Nov 14, 2019 2:45 pm

You have to consider shape and the dipole moments. For example, if a molecule had two polar bonds both pointing towards the central atom and the shape was linear, the dipole moments would cancel (vectors) and the molecule would be non-polar. However, if you had water (where the shape is a tetrahedral) the molecule would be polar because the dipole moments would not cancel.

Andrew Liang 4G
Posts: 53
Joined: Fri Aug 30, 2019 12:18 am

Re: Polarity

Postby Andrew Liang 4G » Thu Nov 14, 2019 2:50 pm

Another tip that I learned from my TA today was that most of the time when the central atom has lone pairs then the molecule is most likely to be polar.

Juana Abana 1G
Posts: 50
Joined: Wed Sep 18, 2019 12:15 am

Re: Polarity

Postby Juana Abana 1G » Thu Nov 14, 2019 6:28 pm

Andrew Liang 4G wrote:Another tip that I learned from my TA today was that most of the time when the central atom has lone pairs then the molecule is most likely to be polar.


Thanks for the tip this is really helpful.

kristi le 1F
Posts: 50
Joined: Thu Jul 11, 2019 12:15 am

Re: Polarity

Postby kristi le 1F » Fri Nov 15, 2019 5:35 pm

A polar molecule must have polar bonds and dimples that do not cancel. A non polar molecule must have zero electric dipole moment.

WesleyWu_3C
Posts: 59
Joined: Thu Jul 25, 2019 12:16 am

Re: Polarity

Postby WesleyWu_3C » Fri Nov 15, 2019 5:53 pm

Something that might help you determine if a molecule is polar is to consider it's shape according to the VSEPR.

505106414
Posts: 55
Joined: Wed Sep 18, 2019 12:17 am

Re: Polarity

Postby 505106414 » Fri Nov 15, 2019 11:58 pm

What is dipole-dipole? I know we talked about it a lot in class but I am still confused.

Amanda Lin 1C
Posts: 51
Joined: Sat Aug 17, 2019 12:15 am

Re: Polarity

Postby Amanda Lin 1C » Sat Nov 16, 2019 1:04 am

Dipole-dipole is the interaction between the partially positive end of a polar molecule and the partially negative end of another polar molecule.

AniP_3B
Posts: 45
Joined: Sat Aug 17, 2019 12:17 am

Re: Polarity

Postby AniP_3B » Sat Nov 16, 2019 12:37 pm

Another tip is that if the atoms around the central atom are not the same (ex. CH3F), then the molecule is very likely to be polar.

105194078
Posts: 52
Joined: Thu Sep 19, 2019 12:17 am

Re: Polarity

Postby 105194078 » Sun Nov 17, 2019 12:58 pm

Andrew Liang 4G wrote:Another tip that I learned from my TA today was that most of the time when the central atom has lone pairs then the molecule is most likely to be polar.

Thank you so much for this! This is very helpful.

105194078
Posts: 52
Joined: Thu Sep 19, 2019 12:17 am

Re: Polarity

Postby 105194078 » Sun Nov 17, 2019 1:05 pm

505106414 wrote:What is dipole-dipole? I know we talked about it a lot in class but I am still confused.

Dipole-Dipole just means a partial positive and a partial negative interaction between molecules.


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