dipole moments

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204929947
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dipole moments

Postby 204929947 » Sun Jun 03, 2018 10:08 pm

I remember Dr.Lavelle discussing dipole moments and how the vectors of the molecules have to cancel in order to be polar. This week in discussion, my TA said something about the length in a vector, how would you know the length?

Zuri Smith 1A
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Re: dipole moments

Postby Zuri Smith 1A » Sun Jun 03, 2018 10:10 pm

Maybe they were talking about the strength of a vector? I'm curious about this too. Also, dipole moments are just created when two atoms have a difference in electronegativities, right?

Perla Cervantes_1G
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Re: dipole moments

Postby Perla Cervantes_1G » Sun Jun 03, 2018 10:13 pm

I was wondering the same exact thing and found this video online to be very helpful in understanding how to determine the length of a vector during a dipole-dipole moment.

https://www.youtube.com/watch?v=ium2E9zKGLE

Chem_Mod
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Re: dipole moments

Postby Chem_Mod » Sun Jun 03, 2018 11:10 pm

C-F vs. C-Cl bonds have different bond polarities since their magnitudes of electronegativity differences are not the same. So their dipole moment vectors will have a different magnitude or size (which is probably what your TA was referring to).

So just roughly speaking, C-F bond will have a dipole moment of -------> while C-Cl bond would have a dipole moment of ---> because of the differences mentioned above. So when determining polarity, you must also consider the magnitude in addition to direction.

Gabi Landes 1-H
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Re: dipole moments

Postby Gabi Landes 1-H » Sun Jun 03, 2018 11:22 pm

Because of the higher strength of electronegativity - would the C-Cl bond be considered more polar?

Chem_Mod
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Re: dipole moments

Postby Chem_Mod » Sun Jun 03, 2018 11:38 pm

F has higher electronegativity than Cl, so C-F would be more polar than C-Cl.

Garrett Dahn 1I
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Re: dipole moments

Postby Garrett Dahn 1I » Sun Jun 03, 2018 11:51 pm

One thing I think is important to generally note here as we are talking about polarity is that the differences in electronegativity merely suggest the relative polarity of a molecule. By that I mean to say that ionic bonds are not fundamentally, irrevocably different covalent bonds, but are rather a sort of augmentation of trends which already persist in covalent bonds. The line between bonds which are considered covalent and ionic is most clearly shown to be blurred with the "polar covalent bond" label, though ionic bonds are really just "very polar covalent bonds" with atoms of such electronegativity disparity as to cause the atoms to behave differently -- exchanging electrons rather than merely sharing them.

Sara Veerman-1H
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Re: dipole moments

Postby Sara Veerman-1H » Mon Jun 04, 2018 6:26 pm

I think they were probably talking about the strength. The polar bonds may not cancel if one is stronger than the other.

Elana Weingord 1C
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Re: dipole moments

Postby Elana Weingord 1C » Thu Jun 07, 2018 4:08 pm

Just to confirm - an increase in the difference between electronegativity will lead to a larger dipole?

Briana Lopez 4K
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Re: dipole moments

Postby Briana Lopez 4K » Thu Jun 07, 2018 4:28 pm

Yeah, he larger the difference in Electronegativity, the more powerful the dipole moment. Also, if there is a strong dipole moment and there is a very unfair sharing of electrons, then the bond is weaker. This is why polar bonds are weaker than nonpolar bonds. Equal sharing = stronger bond= nonpolar bond= no dipole movements or partial charges.


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