## Bond Angles

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

JChen_2I
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

### Bond Angles

Are we just supposed to memorize that a tetrahedral angle is 109.5 degrees and that trigonal planar angles are 107 degrees, etc? Or is there a way that these angles were calculated?

Jorge Ramirez_4H
Posts: 54
Joined: Wed Nov 21, 2018 12:19 am

### Re: Bond Angles

Do we actually need to memorize the bond angles or just what shape they make?

Audrie Chan-3B
Posts: 50
Joined: Thu Jul 25, 2019 12:17 am

### Re: Bond Angles

I think it would be helpful to memorize both bond angles and shape name for the test.

Michelle Le 1J
Posts: 50
Joined: Fri Aug 09, 2019 12:16 am

### Re: Bond Angles

I don't think there's any way to calculate it, so you might just have to memorize what bond angles go with each geometric shape. If you google online, there's plenty of vsepr geometry charts that are helpful!

Eva Zhao 4I
Posts: 101
Joined: Sun Sep 29, 2019 12:16 am

### Re: Bond Angles

Like what others have said, it will probably be helpful to memorize the angles. As a side note, trigonal planar angles are 120 degrees. The 107 degrees was for, i.e. NH3, a molecule with 1 lone pair and 3 bonding pairs.

Kylie Lim 4G
Posts: 110
Joined: Sat Aug 17, 2019 12:15 am

### Re: Bond Angles

I think that you should probably just memorize them since we haven't learned a way to calculate them. Trigonal planar is 120 though not 107.

AveryAgosto
Posts: 76
Joined: Wed Sep 18, 2019 12:16 am

### Re: Bond Angles

I think memorizing them would be a good idea but he didn't specifically say we needed to memorize it.

preyasikumar_2L
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

### Re: Bond Angles

You should just memorize the generic ones: linear=180 degrees, trigonal planar=120 degrees, tetrahedral=109.5 degrees, trigonal bipyramidal=90 and 120 degrees, and octahedral=90 degrees. However, you should also know that having lone pairs will cause the bond angles to be less than the basic amounts, like how in a bent molecule the angle would be <109.5 degrees, so on and so forth.

KnarGeghamyan1B
Posts: 102
Joined: Fri Aug 09, 2019 12:15 am

### Re: Bond Angles

You don't need to memorize every possible exception, just know that in some cases like ammonia and water, the bond angles are slightly less than 109.5 because of the strength of the repulsion of the lone pairs.