Polarity and Shape

[Mirren Solomon Discussion 2G]

When trying to figure out whether or not a molecule is polar or nonpolar, do you have to memorize if each structure is nonpolar/polar or can you figure it out by drawing the diagram?

[Shivani Kapur 2J]

You can draw out the molecule and if it has dipoles that do not cancel, it is polar. You can also have a nonpolar molecule with polar bonds.

[Liam Bertrand 3]

Drawing out the lewis structure with dipole arrows is the best way to figure this out, because you can see if they cancel.

[SLai_1I]

Knowing how to draw Lewis Structures would help you get by without having to memorize structures. You could draw the dipoles on the Lewis Structure and see if they cancel out.

[VincentLe_3A]

The polarity of a molecule depends on both the shape and dipole moments. Drawing out the molecule is the best way to get a full visual representation, which will allow you to see if the dipoles cancel out. The shape does contribute to whether the molecule is polar or non polar, but sometimes molecules can have the same VSEPR shape but one is polar and the other is not. For instance, CO2 has a linear shape and is non polar due to cancelling dipole moments, but HCN is also a linear shape but it is polar due to the dipole difference between hydrogen and nitrogen.

[Sandy Lin 1L]

You would have to draw it out to see if the dipoles cancel out. Both polar and nonpolar molecules can have polar bonds, but the difference is that in nonpolar molecules, you can see that the dipoles will cancel in the polar bonds pulling in opposite directions when you draw it.

[Justin Nguyen 3E]

As everyone above said, I don't think that there is necessarily any way to memorize the polarity of every molecule and the best way to figure out if a molecule is polar or nonpolar is to draw it out because it not only helps you determine polarity but other aspects such as the shape and types of bonds

[Malakai Espinosa 3E]

If you could memorize what shapes create nonpolar molecules, that is perfectly fine. However, for more complex molecules it is also helpful to know how to draw proper lewis structures to analyze whether or not certain polar bonds cancel each other out.

[lwon Dis2I]

How do you know if a molecule is polar?

[Lilly Catarozoli 1B]

I think just drawing them and seeing if the dipoles cancel out is the easiest!

[Mackenzie Stockton 2H]

A molecule is polar if the dipoles on the diagram do not cancel out. So, the bonds themselves must be polar (there must be an electronegativity difference between the 2 atoms) and the bonds cannot cancel out, so there is a charge separation element too.

[Hailey Qasawadish 2J]

You can figure out if a molecule is polar or nonpolar by looking at if the dipoles cancel or not. If they do, it is nonpolar, and if they don't, it is polar. As a general rule, if the molecule has lone pairs, the molecule will be polar. Hope this helps!

[Ethan Goode 2H]

It would be best to know how to draw the lewis structures along with their dipole moments, to see whether or not they cancel out.

[AndrewNguyen_2H]

I see a lot of people saying drawing the Lewis structure with the dipoles to see if they cancel, and although this would probably work a lot of the times, I would caution against this. You have to remember that dipoles exist in 3-dimensional space and not 2 dimensional, so there's room for potential error if you guess based on a Lewis structure. I recommend using Lewis to determine the geometry, and then imagining the structure in 3d space with all the dipoles. 99% of the time you can intuitively guess if the dipoles will not cancel perfectly and are hence polar. Good examples of this are any lone pair or different atoms around the central atom.