Drawing Lewis Structures

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JamieVu_2C
Posts: 108
Joined: Thu Jul 25, 2019 12:16 am

Drawing Lewis Structures

Postby JamieVu_2C » Mon Oct 28, 2019 9:49 pm

When drawing Lewis structures, are you supposed to always draw the different resonance structures and find the formal charges? For example, for 2B. 11C, when drawing H2C(NH2)COOH, if my structure is different from the solution structure, would it be wrong? Or would I have to find the formal charges of the atoms for my structure and keep drawing different structures to match the solution?

kim 2I
Posts: 105
Joined: Thu Jul 25, 2019 12:17 am

Re: Drawing Lewis Structures

Postby kim 2I » Mon Oct 28, 2019 10:04 pm

I don't think it would necessarily be considered wrong, but having a lower formal charge means greater stability, so drawing the Lewis Structure accordingly would be the best answer. Probably if the test specifically asks for the Lewis Structure with the lowest formal charge, then drawing out each one with different resonance might be necessary.

Alex Tchekanov Dis 2k
Posts: 118
Joined: Sat Aug 24, 2019 12:16 am

Re: Drawing Lewis Structures

Postby Alex Tchekanov Dis 2k » Mon Oct 28, 2019 10:42 pm

I agree with the above response, that most of the time you want to draw the one with the lowest formal charge. One kind of short-cut that I've noticed from doing problems that helps me is that when Oxygen has two covalent bonds and 4 lone pairs, it formal charge is zero and when carbon has four covalent bonds, its formal charge is zero -- so when I'm making my first attempt at a lewis structures, I try to roughly stick to these short cuts to keep the formal charges relatively low.

905416023
Posts: 54
Joined: Thu Jul 25, 2019 12:17 am

Re: Drawing Lewis Structures

Postby 905416023 » Mon Oct 28, 2019 11:47 pm

You only have to include additional resonance structures if it asks you to (One of the UA's said this today in a review session). As far as the formal charge goes, I think you should include it just to be safe, but I'm not sure if its always needed. It will help you to determine if your structure is correct though

AlyshaP_2B
Posts: 112
Joined: Wed Sep 18, 2019 12:19 am

Re: Drawing Lewis Structures

Postby AlyshaP_2B » Tue Oct 29, 2019 10:59 am

I think it would be best to play it safe and draw the structure with the lower formal charge because that is the one that is most stable and most likely to be an accurate representation.


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