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dipole moments

Posted: Sun Jun 03, 2018 10:08 pm
by 204929947
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?

Re: dipole moments

Posted: Sun Jun 03, 2018 10:10 pm
by Zuri Smith 1A
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?

Re: dipole moments

Posted: Sun Jun 03, 2018 10:13 pm
by Perla Cervantes_1G
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

Re: dipole moments

Posted: Sun Jun 03, 2018 11:10 pm
by Chem_Mod
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.

Re: dipole moments

Posted: Sun Jun 03, 2018 11:22 pm
by Gabi Landes 1-H
Because of the higher strength of electronegativity - would the C-Cl bond be considered more polar?

Re: dipole moments

Posted: Sun Jun 03, 2018 11:38 pm
by Chem_Mod
F has higher electronegativity than Cl, so C-F would be more polar than C-Cl.

Re: dipole moments

Posted: Sun Jun 03, 2018 11:51 pm
by Garrett Dahn 1I
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.

Re: dipole moments

Posted: Mon Jun 04, 2018 6:26 pm
by Sara Veerman-1H
I think they were probably talking about the strength. The polar bonds may not cancel if one is stronger than the other.

Re: dipole moments

Posted: Thu Jun 07, 2018 4:08 pm
by Elana Weingord 1C
Just to confirm - an increase in the difference between electronegativity will lead to a larger dipole?

Re: dipole moments

Posted: Thu Jun 07, 2018 4:28 pm
by Briana Lopez 4K
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.