Determining Polarity

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AChoudhry_1L
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Determining Polarity

Postby AChoudhry_1L » Wed Nov 13, 2019 9:14 am

How do you determine if a molecule is polar? I know that you would look at the electronegativity, but is there a cut off between what counts as being electronegative enough to be considered polar?

Wendy Perez 1E
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Re: Determining Polarity

Postby Wendy Perez 1E » Wed Nov 13, 2019 9:20 am

In order to determine if a molecule is polar, you have to look at the shape and the differences in electronegativity. There is no cutoff in electronegativity. If the dipole moments all cancel, the molecule is nonpolar. If the dipole moments do not cancel, the molecule is polar.

Chem_Mod
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Re: Determining Polarity

Postby Chem_Mod » Wed Nov 13, 2019 9:22 am

There a few different cutoffs. Using the pauling scale of electronegativity (link below), generally we can say if the difference in electronegativity is about 0.5 or greater we can say it's a polar bond and the molecule may be polar. If it's greater than 1.5 - 2 or greater, it becomes ionic. However, it will vary from book to book. You do also have to consider shape as well, as dipoles may cancel depending on the shape.

https://en.wikipedia.org/wiki/Template: ... ling_scale)

Leila_4G
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Re: Determining Polarity

Postby Leila_4G » Wed Nov 13, 2019 9:03 pm

So, just to be sure, if it is a nonmetal + alkaline earth metal, it is polar molecule?

Nare Nazaryan 1F
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Re: Determining Polarity

Postby Nare Nazaryan 1F » Wed Nov 13, 2019 10:25 pm

Yes, the difference in electronegativity should be about 0.5 to be considered polar. Shape also plays a role in terms of the possibility of dipole moments canceling.

Julieta Serobyan4D
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Joined: Wed Sep 11, 2019 12:17 am

Re: Determining Polarity

Postby Julieta Serobyan4D » Wed Nov 13, 2019 10:35 pm

Leila_4E wrote:So, just to be sure, if it is a nonmetal + alkaline earth metal, it is polar molecule?

Yes, basically ionic bonds makes them polar


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