Helpful Chart

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

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DomMaiorca_1I
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Helpful Chart

Postby DomMaiorca_1I » Thu May 31, 2018 10:25 am

This post doesn't have a question, just a chart from my TA that might make memorization easier!

# of regions of e- density. arrangement of e- densities (bond angles).
2 linear (180)
3 trigonal planar (120)
4 tetrahedral (109.5)
5 trigonal bipyramidal (120, 90)
6 octahedral (90)

AnnaYan_1l
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Re: Helpful Chart

Postby AnnaYan_1l » Thu May 31, 2018 10:50 am

This helps so much, thank you!!! I was super worried about memorizing them.

Rebekah Kaufman 1L
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Re: Helpful Chart

Postby Rebekah Kaufman 1L » Thu May 31, 2018 11:04 am

Is there a way to calculate the bond angles or is it just a memorization thing?

Kaleb Tesfaye 1I
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Re: Helpful Chart

Postby Kaleb Tesfaye 1I » Thu May 31, 2018 11:30 am

Hey Rebekah. Based on what I have seen so far, it seems like you have to memorize them.

Hussein Saleh 1L
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Re: Helpful Chart

Postby Hussein Saleh 1L » Thu May 31, 2018 3:27 pm

Rebekah Kaufman 1L wrote:Is there a way to calculate the bond angles or is it just a memorization thing?


Unfortunately, Its the one thing we MUST memorize for the course. It should not be too hard though with practice we should be fine while also strengthing our lewis structure skills!

Jennifer 1G
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Re: Helpful Chart

Postby Jennifer 1G » Fri Jun 01, 2018 7:33 pm

We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the exact number, just know that it's less than 109.5.

CarinaVargas1J
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Re: Helpful Chart

Postby CarinaVargas1J » Sun Jun 03, 2018 11:41 pm

Thank you for sharing it with us. It is helpful. (:

melodyso1K
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Re: Helpful Chart

Postby melodyso1K » Mon Jun 04, 2018 6:11 pm

Jennifer 1G wrote:We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the exact number, just know that it's less than 109.5.

I remember this too but I don't quite remember for what instances the angle would be less than 109.5 degrees, can anybody explain why?

Sara Veerman-1H
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Re: Helpful Chart

Postby Sara Veerman-1H » Mon Jun 04, 2018 6:14 pm

Thank you so much!

melodyso1K
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Re: Helpful Chart

Postby melodyso1K » Mon Jun 04, 2018 6:15 pm

This chart is indeed helpful, thanks for sharing!

AnnaYan_1l
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Re: Helpful Chart

Postby AnnaYan_1l » Sun Jun 10, 2018 5:24 pm

melodyso1K wrote:
Jennifer 1G wrote:We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the exact number, just know that it's less than 109.5.

I remember this too but I don't quite remember for what instances the angle would be less than 109.5 degrees, can anybody explain why?


Hi! This would mostly have to do with the molecules in the formula. Here’s what I have in my notes:

Molecules with the same formula have the same general shape but their bond angles may differ slightly.
For example, comparing the difference between CH4 and CH3Cl, both have the VSEPR formula AX4 and thus have a tetrahedral shape. However, in CH3Cl, chlorine is larger than hydrogen, which pushes the other atoms further away than would just the 4 H atoms in CH4. This thus changes the angles.

So, even though the molecules are both AX4, their bond angles differ slightly.

Hope this helps!

Moris 1H
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Re: Helpful Chart

Postby Moris 1H » Sun Jun 10, 2018 5:50 pm

How do we memorize angles if sometimes the angle depends on that specific molecule's lone pair composition?

Luis Torres 1C
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Re: Helpful Chart

Postby Luis Torres 1C » Sun Jun 10, 2018 6:30 pm

AnnaYan_1B wrote:
melodyso1K wrote:
Jennifer 1G wrote:We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the exact number, just know that it's less than 109.5.

I remember this too but I don't quite remember for what instances the angle would be less than 109.5 degrees, can anybody explain why?


Hi! This would mostly have to do with the molecules in the formula. Here’s what I have in my notes:

Molecules with the same formula have the same general shape but their bond angles may differ slightly.
For example, comparing the difference between CH4 and CH3Cl, both have the VSEPR formula AX4 and thus have a tetrahedral shape. However, in CH3Cl, chlorine is larger than hydrogen, which pushes the other atoms further away than would just the 4 H atoms in CH4. This thus changes the angles.

So, even though the molecules are both AX4, their bond angles differ slightly.

Hope this helps!


Everything said so far is absolutely correct (to the best of my knowledge). I just wanted to present an additional situation with changed bond angles, which Jennifer touched upon in her original question. Lone pair electrons have a high repulsion strength, so if a molecule has a lone pair (or multiple lone pairs), this too could decrease bond angles.

204929947
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Re: Helpful Chart

Postby 204929947 » Sun Jun 10, 2018 8:40 pm

Jennifer 1G wrote:We made a similar chart in discussion too. I want to point out that I believe our TA mentioned something about the angles being less than 109.5 in some cases, I'm not exactly sure why or in what instances, but I think he mentioned lone pairs. I also think Lavelle said that we don't have to know the exact number, just know that it's less than 109.5.

the angles would be >109.5 when there is a lone pair involved in the # of e- densities around a molecule

Chem_Mod
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Re: Helpful Chart

Postby Chem_Mod » Sun Jun 10, 2018 9:49 pm

the angles would be >109.5 when there is a lone pair involved in the # of e- densities around a molecule


The angles would be less than, not greater than.

Isobel Tweedt 1E
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Re: Helpful Chart

Postby Isobel Tweedt 1E » Sun Jun 10, 2018 10:17 pm

Just to be clear, they are less than because the loan electron pair pushes the other atoms farther away from it (and thus closer to other atoms). This then results in increasingly smaller angles between atoms as you move left to right along the chart.

melodyso1K
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Re: Helpful Chart

Postby melodyso1K » Mon Jun 11, 2018 12:06 am

These were all very great and very helpful, thanks everyone!

Andrea Raymundo 1B
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Re: Helpful Chart

Postby Andrea Raymundo 1B » Wed Jun 13, 2018 1:10 am

when one of those regions is lone pair or pairs, is it basically the same thing but just with > or < ?

Andrea Raymundo 1B
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Re: Helpful Chart

Postby Andrea Raymundo 1B » Wed Jun 13, 2018 1:11 am

when one of those regions is lone pair or pairs, is it basically the same thing but just with > or < ?


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