Ch.3 #95

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

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Simone Seliger 1C
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Joined: Fri Sep 25, 2015 3:00 am

Ch.3 #95

Postby Simone Seliger 1C » Wed Oct 28, 2015 11:28 pm

The compound given is C(H2)3 with charge of 2-. Do we only draw bonds for connecting the 3 CH2 compounds to the central carbon? I first bonds for all of the atoms, but the solutions manual showed to do otherwise. Is that because molecular shape/resonance only depends on the central atom? If so, what happens to how we keep track of the valence electrons in the Lewis structure?

Hannah Markovic 3C
Posts: 32
Joined: Fri Sep 25, 2015 3:00 am

Re: Ch.3 #95

Postby Hannah Markovic 3C » Thu Oct 29, 2015 10:05 am

I think the solutions didn't draw the bonds between the carbon and hydrogen just because they were kind of being lazy/simplifying the lewis structure. Usually in organic chem you will draw CH2s like that because you know that the carbon will just have one bond with each hydrogen so it isn't really necessary to draw the bonds. If you notice the picture makes sure to always draw the bonds connecting with the C in CH2. The bonds within the CH2 groups still exist. We haven't gone over that yet though so for tests and stuff I would draw all the bonds until someone says otherwise. So yeah to keep track of the valence electrons you should draw out the entire structure first, and then after if you wanted to make it look simpler/more compact you could substitute in the CH2s (but I wouldn't yet). Basically the book just wanted to make the structure simpler and focus on the single and double bonds between the carbons. So all in all don't worry about it :) If you drew all the bonds it would be fine.

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