Bond Angles

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

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Anika Chakrabarti 1A
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Joined: Sat Aug 24, 2019 12:17 am

Bond Angles

Postby Anika Chakrabarti 1A » Sat Nov 16, 2019 9:42 am

How do we predict the bond angles of a molecule?

Rebekah Alfred 1J
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Joined: Thu Jul 11, 2019 12:15 am
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Re: Bond Angles

Postby Rebekah Alfred 1J » Sat Nov 16, 2019 10:18 am

I believe we should know the bond angles of the molecular shapes we go over during lecture (i.e. Linear-180 degrees & Tetrahedral-109.5 degrees). We predict bond angles when there are lone pairs on the central atom, which influence the molecular shape and affect the bond angle. For example, we can predict that the sulfite ion (the central atom has 1 lone pair and 3 bonding pairs) will have a bond angle of slightly less than 109.5 degrees since the 4 pairs are arranged tetrahedrally around the central atom to reduce repulsion.

Izzie Capra 2E
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Joined: Sat Sep 07, 2019 12:19 am

Re: Bond Angles

Postby Izzie Capra 2E » Sat Nov 16, 2019 10:48 am

Yes, and the more lone pairs a molecule has, the more repulsion it experiences, so the bond angle will become smaller than the one you can predict based off of the shape.

Maya Pakulski 1D
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Re: Bond Angles

Postby Maya Pakulski 1D » Sat Nov 16, 2019 1:38 pm

So we basically just have to memorize which bond angles go with which shapes?

Ellen Amico 2L
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Joined: Thu Sep 19, 2019 12:16 am

Re: Bond Angles

Postby Ellen Amico 2L » Sat Nov 16, 2019 1:45 pm

Maya Pakulski 3D wrote:So we basically just have to memorize which bond angles go with which shapes?

Yes that's honestly the easiest way, but conceptually you should know that the reason the bond angles occur is due to repulsion between lone pairs and bonding pairs.

RRahimtoola1I
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Joined: Fri Aug 09, 2019 12:15 am

Re: Bond Angles

Postby RRahimtoola1I » Sat Nov 16, 2019 2:14 pm

It's probably easiest to just memorize a chart with all the bond angles stated, but for the test he said we just have to be able to say that a trigonal pyramidal shape has a smaller bond angle than a tetrahedral because of the lone pair having more repulsion than the bonded pair.

Hannah Romano 4D
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Joined: Sat Aug 24, 2019 12:18 am

Re: Bond Angles

Postby Hannah Romano 4D » Sat Nov 16, 2019 2:24 pm

if you can remember the bond angles of the basic molecular geometries containing no lone pairs (i.e. linear=180, trigonal planar=120, tetrahedral=109.5, trigonal bipyramidal=120, 90, & 180, and octahedral= 90) then you can predict that the bond angles with be slightly less than these numbers when lone pairs are added because of the higher repulsion of lone pairs.

Anvi Brahmbhatt 4A
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Joined: Wed Sep 18, 2019 12:21 am

Re: Bond Angles

Postby Anvi Brahmbhatt 4A » Sat Nov 16, 2019 3:10 pm

The easiest way is to memorize which bond angles go with which shapes. However, do understand the concepts behind why certain bond angles are formed.

faithkim1L
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Joined: Fri Aug 09, 2019 12:17 am

Re: Bond Angles

Postby faithkim1L » Sat Nov 16, 2019 3:12 pm

The angles for the molecular shapes are all standardized. When a molecule is polar, the bond angles will change, but we do not need to know the exact values. All we need to indicate is that the angles either decrease or increase (i.e. with lone pairs of electrons instead of bonding pairs).

ATingin_3I
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Joined: Fri Aug 30, 2019 12:17 am

Re: Bond Angles

Postby ATingin_3I » Sat Nov 16, 2019 3:27 pm

RRahimtoola1G wrote:It's probably easiest to just memorize a chart with all the bond angles stated, but for the test he said we just have to be able to say that a trigonal pyramidal shape has a smaller bond angle than a tetrahedral because of the lone pair having more repulsion than the bonded pair.

but for this we don't have to know the bond angle exactly, just that it is less than and why?


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