Determining Shape

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

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chrisavalos-2L
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

Determining Shape

Postby chrisavalos-2L » Sat Nov 17, 2018 11:04 pm

I was wondering if there was an easy short way in determining the shape of a molecule based on its molecular formula without drawing the Lewis structure first? Or is the Lewis structure necessary for determining the shape?

Tony Ong 3K
Posts: 63
Joined: Fri Sep 28, 2018 12:23 am

Re: Determining Shape

Postby Tony Ong 3K » Sat Nov 17, 2018 11:22 pm

you want to draw out the lewis structure always to determine what the Steric Number is for the central atom...then you can determine shape from there.
Don't cheat your way with shortcuts!!!! It'll be your ultimate downfall!

oh and steric number means bonded pairs of electrons (double bond counts as one) AND lone pairs of electrons

have a good thanksgiving :)

Tony Ong 3K
Posts: 63
Joined: Fri Sep 28, 2018 12:23 am

Re: Determining Shape

Postby Tony Ong 3K » Sat Nov 17, 2018 11:25 pm

you want to draw out the lewis structure always to determine what the Steric Number is for the central atom...then you can determine shape from there.
Don't cheat your way with shortcuts!!!! It'll be your ultimate downfall!

oh and steric number means bonded pairs of electrons (double bond counts as one) AND lone pairs of electrons

have a good thanksgiving :)

MinaChoi_3H
Posts: 31
Joined: Fri Sep 28, 2018 12:25 am

Re: Determining Shape

Postby MinaChoi_3H » Sat Nov 17, 2018 11:54 pm

You will always need to draw the lewis structure because a compound can have numerous structures drawn and you need to find the one with the lowest energy to be able to find the correct shape as well as the reason mentioned above.

Karla_Ocampo 4E
Posts: 32
Joined: Tue Nov 21, 2017 3:01 am

Re: Determining Shape

Postby Karla_Ocampo 4E » Sun Nov 18, 2018 11:12 am

I think its best to always draw the lewis structure so you can get the most accurate answer. This way you will be able to find the shape, lone pairs, etc..

Hanlin Zhu 4G
Posts: 30
Joined: Fri Sep 28, 2018 12:28 am

Re: Determining Shape

Postby Hanlin Zhu 4G » Sun Nov 18, 2018 12:08 pm

It is hard to know the number of bonding pairs and lone pairs just by looking at the chemical formula. I think to be safe we have to draw the lewis structure.

Ruiting Jia 4D
Posts: 65
Joined: Fri Sep 28, 2018 12:27 am

Re: Determining Shape

Postby Ruiting Jia 4D » Sun Nov 18, 2018 1:33 pm

I think besides just drawing the Lewis structure, what would also help is sketching or imagining the Lewis structure in 3d. The Lewis structure presents you with a very 2d linear version of what the model actually looks like.

Madeline Motamedi 4I
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

Re: Determining Shape

Postby Madeline Motamedi 4I » Sun Nov 18, 2018 4:19 pm

It's good to get in the habit of drawing the lewis structure and as you do them more and more it'll be easier and you'll become faster at drawing them.

Nick Bazett 1F
Posts: 32
Joined: Fri Sep 28, 2018 12:15 am

Re: Determining Shape

Postby Nick Bazett 1F » Sun Nov 18, 2018 4:27 pm

My TA said we can either memorize every shape, or use your intuition. She also said to draw them out.

Nicole Jakiel 4F
Posts: 32
Joined: Fri Sep 28, 2018 12:28 am

Re: Determining Shape

Postby Nicole Jakiel 4F » Sun Nov 18, 2018 4:38 pm

For now I would really just draw the Lewis Structures every time- eventually you may begin to pick up on certain patterns but as of right now drawing the Lewis Structure first is the best way to go!

Estelle Jung
Posts: 31
Joined: Fri Sep 28, 2018 12:29 am

Re: Determining Shape

Postby Estelle Jung » Sun Nov 18, 2018 7:04 pm

In order to determine molecular shape, you should be able to find the steric number, which is the number of atoms and lone pairs bonded to the central atom.


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