bond angles

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

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Katie Bart 1I
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Joined: Sat Aug 24, 2019 12:16 am

bond angles

Postby Katie Bart 1I » Thu Nov 14, 2019 10:30 am

In VSEPR molecules that have varying bond angles between atoms, how do we know which angle degrees are where in the molecule?

Abhi Vempati 2H
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

Re: bond angles

Postby Abhi Vempati 2H » Thu Nov 14, 2019 10:42 am

I'm pretty sure it's just something you have to memorize. For some molecules it's pretty intuitive (ex: since CO2 is a linear molecule, the bond angle is 180 degrees), but once you get to the more complicated molecules, you just have to memorize them. There's a chart in the textbook/online to help with that. Additionally, for most molecules that we have to list the bond angles for, the bonded atoms are all usually the same (ex: SF6), so you won't have to worry about placing the bonded atoms in the right place. Finally, like Professor Lavelle mentioned, we don't really need to worry about what goes where because we won't be asked to draw the molecules. All we need to know are the bond angles themselves. Hope this helps!

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Re: bond angles

Postby LReedy_3I » Thu Nov 14, 2019 1:38 pm

Being able to visualize how the molecules look 3 dimensionally is really helpful, and being able to apply that to the Lewis structure to understand where in the molecule each atom it is. There are diagrams in the book for each shape we've talked about

Brandon Valafar
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Re: bond angles

Postby Brandon Valafar » Thu Nov 14, 2019 2:03 pm

You could try to visualize the model of each shape, however I believe it's just one of those things you have to memorize. It will most likely be tested on so make sure you have it down.

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Re: bond angles

Postby 805097738 » Thu Nov 14, 2019 4:33 pm

i'd memorize the examples that lavelle went over in class

Quynh Vo
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Joined: Sun Sep 29, 2019 12:15 am

Re: bond angles

Postby Quynh Vo » Thu Nov 14, 2019 7:14 pm

It depends on the shape of the molecule which can a useful method to remember angles. For example, if it's linear, they're 180 degrees from another. Trigonal planar models are usually 120 degrees from each other and tetrahedral are 109.5 degrees from each other.

Fdonovan 3D
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Joined: Sat Aug 17, 2019 12:16 am

Re: bond angles

Postby Fdonovan 3D » Thu Nov 14, 2019 8:07 pm

I'm not sure if memorization is the best method for this but that's the method I'm doing..
Linear is easy-- it's 180 degrees because they're literally just in a line. Beyond that though, it's easier to see if you have a 3D model in front of you (which I'm sure you don't) but I'll just write out the rest anyway. Trigonal planar has 120 degree bonding angles. Tetrahedral structure has bond angles of 109.5 degrees. Trigonal bipyramidal has bond angles of 120 degrees, with axial bonds of either 90 or 180 degrees. Finally, octahedral structure has bond angles of either 90 or 180 degrees.
Not sure if we need to know all this, but this is just a quick reference guide.

Jorge Ramirez_4H
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Re: bond angles

Postby Jorge Ramirez_4H » Thu Nov 14, 2019 9:36 pm

Would question actually ask for bond angles?

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Re: bond angles

Postby Aprice_1J » Fri Nov 15, 2019 12:07 am

Can someone explain why you get angle degrees of 109.5 and 120? I understand 180 and 90 but I'm not sure what shape/measurement would lead to either 109.5 or 120.

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Joined: Sat Sep 07, 2019 12:15 am

Re: bond angles

Postby 005321227 » Fri Nov 15, 2019 12:23 am

Simply look at the. lone pairs and bonds in the molecule top determine your answer

Jedrick Zablan 3L
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Joined: Sat Aug 17, 2019 12:17 am

Re: bond angles

Postby Jedrick Zablan 3L » Fri Nov 15, 2019 12:33 am

I think the key would be just memorizing the bond angles of each shape, or at least see the pattern of what shapes look like and how similar shapes have similar or same bond angles.

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