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How to identify polarity

Posted: Wed Nov 28, 2018 10:08 pm
by melissa_dis4K
I'm having a lot of trouble understanding polarity, can someone please help and explain how it is that we identify polar molecules. I know that polar is the unequal sharing of electrons and that if the dipole moments cancel it is nonpolar. However, I am just having trouble applying it to the actual structures. And does the structure matter when cancelling out polarity? For example, if it's bent does it not cancel, like in H2O?

Re: How to identify polarity

Posted: Wed Nov 28, 2018 10:19 pm
by Patrick Cai 1L
Polar molecules have one thing in common: a net nonzero dipole moment. To determine the dipole moment, one must consider the spatial distribution of the atoms and electron clouds, as well as the differences in electronegativity between the bonded atoms. For instance, in the case of H2O, both the electronegativity difference between hydrogen and oxygen and the bent molecular shape of H2O contribute to the molecule's polarity.

Re: How to identify polarity

Posted: Wed Nov 28, 2018 10:53 pm
by Jeffrey Xiao 4A
Usually lone pairs make the molecule polar but there are exceptions with the linear AX2E3 and square planar AX4E2 where the molecules are nonpolar because dipole moments cancel regardless of the lone pairs,
Otherwise, all the shapes with no lone pairs are nonpolar (tetrahedral, trigonal planar, octahedral, etc) IF the bonded atoms are all the same (CCl4 or CH4) not (CH2Cl2 or CH3Cl) which are polar.