Polarity

(Polar molecules, Non-polar molecules, etc.)

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Abigail Menchaca_1H
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

Polarity

Postby Abigail Menchaca_1H » Sun Nov 24, 2019 8:09 pm

How can you tell when forces within a molecule cancel out?

Eugene Chung 3F
Posts: 142
Joined: Wed Nov 15, 2017 3:03 am

Re: Polarity

Postby Eugene Chung 3F » Sun Nov 24, 2019 8:15 pm

I would first draw the lewis structure, identify the vsepr shape to find out if the molecule is symmetrical or not. If it is symmetrical then it is most likely nonpolar since the dipole moments will cancel out. But if it isn’t symmetrical, draw the dipole moment arrows (towards the more electronegative one) and see if the arrows cancel each other out.

vpena_1I
Posts: 109
Joined: Sat Aug 24, 2019 12:15 am

Re: Polarity

Postby vpena_1I » Sun Nov 24, 2019 8:16 pm

If they are the same atom directly opposite of each other, they will cancel, as in the case of CH4, but if just one of those hydrogens is different, as in CH3Cl, they won't cancel completely and will result in a dipole.

Harry Zhang 1B
Posts: 101
Joined: Sat Sep 14, 2019 12:16 am

Re: Polarity

Postby Harry Zhang 1B » Sun Nov 24, 2019 8:21 pm

Just like how vectors can only cancel out each other when they are opposite to each other, you can draw out the dipole moment in a molecule and see if they cancel, but you must solve this by using the VSEPR model instead of the lewis structure since the VSEPR gives a more accurate 3D shape. A special case is the tetrahedral shape and tetrahedral-shaped molecule is only nonpolar when all atoms bonded to the central atom are the same; you might think their dipole moments are not directly opposite to each other but since there is no preferred site of interaction when there is the same magnitude of dipole moment in every direction, it is considered to be non polar.

Sreyes_1C
Posts: 90
Joined: Fri Sep 28, 2018 12:19 am

Re: Polarity

Postby Sreyes_1C » Sun Nov 24, 2019 8:57 pm

if they have the same pull opposite of each other, like 4 of the same atoms surrounding a central atom, they will cancel out.


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