Formal Charge Equation?


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Michelle N - 2C
Posts: 75
Joined: Wed Sep 18, 2019 12:19 am

Formal Charge Equation?

Postby Michelle N - 2C » Thu Nov 07, 2019 9:52 am

I noticed that there are two equations:

FC = V + (L+B) and FC = V + (L + B/2).

Both depend on how you count the shared bond?

SnehinRajkumar1L
Posts: 60
Joined: Thu Jul 11, 2019 12:15 am

Re: Formal Charge Equation?

Postby SnehinRajkumar1L » Thu Nov 07, 2019 10:03 am

Yes, that is correct. The first one treats each bond as 1 electron, the other treats it as 2.

Jaci Glassick 2G
Posts: 68
Joined: Sat Jul 20, 2019 12:16 am

Re: Formal Charge Equation?

Postby Jaci Glassick 2G » Thu Nov 07, 2019 10:04 am

In the first equation, you count the number of actual bonds (so for a double bond, you would count 2 bonds so you plug 2 in for B). In the second, B is the number of electrons shared by the bonds (a double bond shared 4 electrons, so you plug 4 into B). I hope this helps!

Victoria Otuya 4F
Posts: 50
Joined: Wed Sep 18, 2019 12:21 am

Re: Formal Charge Equation?

Postby Victoria Otuya 4F » Thu Nov 07, 2019 9:19 pm

I learned an easier way to remember the formal charge equation: valence electron -(dots + line).

Destiny_Ryales_3J
Posts: 38
Joined: Fri Sep 28, 2018 12:28 am

Re: Formal Charge Equation?

Postby Destiny_Ryales_3J » Thu Nov 07, 2019 9:32 pm

do you include the subscripts between different elements in your calculations?

Lauren Sanchez 3D
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Joined: Sat Aug 24, 2019 12:17 am

Re: Formal Charge Equation?

Postby Lauren Sanchez 3D » Thu Nov 07, 2019 10:03 pm

Victoria Otuya 4F wrote:I learned an easier way to remember the formal charge equation: valence electron -(dots + line).

That is a really good way to remember it!

PGao_1B
Posts: 50
Joined: Sat Jul 20, 2019 12:15 am

Re: Formal Charge Equation?

Postby PGao_1B » Sat Nov 09, 2019 12:02 am

Yes, both depend on how you count the shared bond. The first equation treats the number of bonds as how many "lines" you draw as bonds, while the second equation treats the number of bonds as the amount of valence electrons that are shared in total between an atom and another respective atom. Both are correct, and should give you the same, accurate answer.

305416361
Posts: 50
Joined: Fri Aug 09, 2019 12:17 am

Re: Formal Charge Equation?

Postby 305416361 » Sun Nov 10, 2019 12:20 am

Victoria Otuya 4F wrote:I learned an easier way to remember the formal charge equation: valence electron -(dots + line).


does this count "dots" as pairs of dots or individual ones?

Christine Honda 2I
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Joined: Sat Sep 14, 2019 12:17 am

Re: Formal Charge Equation?

Postby Christine Honda 2I » Sun Nov 10, 2019 1:39 pm

305416361 wrote:
Victoria Otuya 4F wrote:I learned an easier way to remember the formal charge equation: valence electron -(dots + line).


does this count "dots" as pairs of dots or individual ones?


Count each dot as one electron each.

Rohan Kubba Dis 4B
Posts: 50
Joined: Sat Aug 17, 2019 12:18 am

Re: Formal Charge Equation?

Postby Rohan Kubba Dis 4B » Sun Nov 10, 2019 2:03 pm

Also, my TA I taught us a really easy way:

Valence electrons of element-(number of bonds(lines) + the number of lone electrons(not pairs)). This seemed to work for me and it was fast too. Another trick I learned was that when finding the formal charge for oxygen, if it was double bonded and had two loan pairs of electrons, it had a formal charge of zero.

gferg21
Posts: 51
Joined: Sat Aug 17, 2019 12:17 am

Re: Formal Charge Equation?

Postby gferg21 » Sun Nov 10, 2019 3:39 pm

The best way to do it is the first equation you put down. It needs less steps to figure it out, which could mean more time for questions on tests. The (b/2) seems a bit unnecessary but I understand that it is just to show that only one electron is actually the individual atom's.

Mallika Chimpiri 3K
Posts: 58
Joined: Thu Jul 25, 2019 12:17 am

Re: Formal Charge Equation?

Postby Mallika Chimpiri 3K » Sun Nov 10, 2019 3:47 pm

In the first equation, B is counted as a bond, while in the second equations B is counted as each shared electron. That's why when counted as singular electrons, it has to be divided by 2 to account for the bonds.

Leyna Dang 2H
Posts: 66
Joined: Thu Jul 25, 2019 12:17 am

Re: Formal Charge Equation?

Postby Leyna Dang 2H » Sun Nov 10, 2019 4:41 pm

You could use Formal Charge= Valence Electrons + (Lone Pairs - Bonds/2), but an easier way to calculate the formal charge is to check the valence electron of the element and subtract the number of dots and lines it has.


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