Polar or Nonpolar

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Sunia Akaveka 4I
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Polar or Nonpolar

Postby Sunia Akaveka 4I » Wed Nov 20, 2019 10:58 pm

How exactly do you determine if a molecule is polar or nonpolar? I understand it mainly regards to dipoles canceling out or not, but can anybody elucidate this concept, I'm not quite fully understanding. Thanks!

Sophia Shaka 3L
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Re: Polar or Nonpolar

Postby Sophia Shaka 3L » Wed Nov 20, 2019 11:16 pm

If the molecule has mirror symmetry, the dipoles will cancel and the net dipole will be zero, therefore it'll be nonpolar. Monatomic compounds will be nonpolar since there's no electronegativity difference. If there's not symmetry and it's polyatomic, often the more electronegative species will pull electrons towards it creating polarity. Just look at the electronegativity difference to determine if this will be the case.

VPatankar_2L
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Re: Polar or Nonpolar

Postby VPatankar_2L » Fri Nov 22, 2019 3:16 pm

Generally, you can look at the terminal toms to determine whether a structure will be polar or polar. With linear, trigonal planar, and tetrahedral structures, if the terminal atoms are the same the molecules will be nonpolar. But if the terminal atoms are different, the molecules will be polar. Regarding bent and pyramidal structures, the molecule will be polar regardless of whether or not the terminal toms are the same or different

serenabirkhoff_1K
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Re: Polar or Nonpolar

Postby serenabirkhoff_1K » Fri Nov 22, 2019 3:39 pm

Additionally, there is a table on page 113 in the textbook that helped me a lot with understanding polar and nonpolar. It also helped visualize polar and nonpolar with the shape of the molecule and VSEPR formula, withe examples. The figure is 2E.7 on page 113.

005321227
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Re: Polar or Nonpolar

Postby 005321227 » Fri Nov 22, 2019 7:27 pm

Always look at the symmetry of a molecule first. If a molecule is symmetrical, it is non polar. If not, find the Mose electronegative atom and that is the slightly negative end of a polar molecule

Ally Huang- 1F
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Re: Polar or Nonpolar

Postby Ally Huang- 1F » Fri Nov 22, 2019 9:03 pm

Another thing to remember when determining polarity is that many of these structures are 3 dimensional. For example, with CH2Cl2, placing the Cl atoms opposite each other and placing the H atoms opposite each other may seem like the dipoles would cancel, however due to the 3 dimensional shape the dipoles don't cancel and the molecule is still polar.


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