formal charge


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Sophia Dinh 1D
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

formal charge

Postby Sophia Dinh 1D » Tue Nov 12, 2019 2:07 pm

How can you determine the formal charge without the equation?

Kallista McCarty 1C
Posts: 212
Joined: Wed Sep 18, 2019 12:18 am

Re: formal charge

Postby Kallista McCarty 1C » Tue Nov 12, 2019 2:10 pm

You count the number of bonds that the element has and compare it to the number of valence electrons that it should have!

Ananta3G
Posts: 62
Joined: Wed Sep 18, 2019 12:19 am

Re: formal charge

Postby Ananta3G » Tue Nov 12, 2019 2:25 pm

If you already have the Lewis Dot Drawing of the molecules correctly completed, you can just count the number of electrons around the atom by counting up each electron of the lone pair as one electron and each bonded pair as one electron as well ie 1 for a single bond, 2 for a double bond, etc. and compare that sum to the number of valence electrons you know the atom should have according to the periodic table to get the formal charge.

MAC 4G
Posts: 121
Joined: Wed Sep 18, 2019 12:16 am

Re: formal charge

Postby MAC 4G » Tue Nov 12, 2019 2:37 pm

Either way is fine if you get to the correct answer, but on an exam I think it's better to write out using the formula because in doing so, I believe it'll get you some partial credit if you were to make a mistake when drawing a Lewis structure or a resonance hybrid.

kristi le 2F
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am

Re: formal charge

Postby kristi le 2F » Sun Nov 17, 2019 8:41 pm

Also, with enough practice, you can remember how many lone pairs and bonding pairs like to have. For example, Oxygen likes to have 2 lone pairs and 2 bonding pairs because this gives it a formal charge of zero.

505106414
Posts: 55
Joined: Wed Sep 18, 2019 12:17 am

Re: formal charge

Postby 505106414 » Tue Nov 19, 2019 8:31 pm

A very simplified/juvenile way to think of formal charge is FC = Valence E - (# sticks + # dots). Sticks being bonds and dots being single electrons in lone pairs.

anjali41
Posts: 109
Joined: Fri Aug 09, 2019 12:15 am

Re: formal charge

Postby anjali41 » Tue Nov 19, 2019 8:37 pm

First you should look at the periodic table and determine how many valence electrons that the element should have. Next, count the total electrons present in the form of both lone pairs and bonds. Then compare this to the ideal number of valence electrons that the element should have. If there are more electrons, the formal charge will be negative. If there are fewer electrons present, then the formal charge will be positive.


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