Calculating formal charge

$FC=V-(L+\frac{S}{2})$

Jorja De Jesus 2C
Posts: 121
Joined: Sat Jul 20, 2019 12:15 am

Calculating formal charge

When calculating formal charge, which atoms to you calculate first, the central atom or the surrounding ones? Do you add up all their charges in the end?

Lauren Stack 1C
Posts: 100
Joined: Sat Aug 17, 2019 12:18 am

Re: Calculating formal charge

When calculating formal charge, the order that you do it in should not matter. Formal charge is assigned individually to each atom in a molecule by taking the number of valence electrons and subtracting the sum of the number of bonds and the number of lone electrons. Overall, you want the most electronegative atom to have the most negative formal charge. The least electronegative atom in the molecule is typically the central atom, which is something you can take into account when thinking about estimating formal charges on individual atoms.
As for adding the charges in the end, I believe you want the sum of the formal charges to match the overall charge of the molecule.

Kehlin Hayes 4C
Posts: 50
Joined: Wed Sep 18, 2019 12:17 am

Re: Calculating formal charge

It does not matter, it is best to calculate the formal charge of each atom to see if you have the desired overall formal charge of the molecule.

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

Re: Calculating formal charge

It doesn't matter what atom you start with because you are finding the individual charges for each atom. To find the charge of the molecule you would add up the charges of each individual atom.

The most favorable formal charge is zero because it means the molecule is stable.

Emil Velasco 1H
Posts: 96
Joined: Wed Nov 21, 2018 12:19 am

Re: Calculating formal charge

Doesn't matter where you start as long as the overall FC of the molecule matches what is given or is at the most favorable FC which is 0.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

Re: Calculating formal charge

You should just calculate the formal charges of all the atoms, and use all of them to determine whether or not you need to change the structure (bonds/lone pairs).

Michelle Song 1I
Posts: 102
Joined: Thu Jul 11, 2019 12:17 am

Re: Calculating formal charge

It doesn't matter which one you calculate first.

Natalie Benitez 1E
Posts: 100
Joined: Fri Aug 02, 2019 12:15 am

Re: Calculating formal charge

When calculating formal charge the order doesn't matter because each element has there own formal charge. This is calculated through subtracting the number of bonds a lone pair electrons from the valence electron of that given element. As for adding the charges at the end, the only thing you should be wary of is the fact that the end result should match the overall charge of the molecule.

Kaitlynn Tran 3F
Posts: 54
Joined: Wed Sep 18, 2019 12:20 am

Re: Calculating formal charge

It doesn't matter which order you calculate formal charge in because each atom's formal charge should be counted individually. You don't need to add up the formal charges at the end, but you can compare each atom's formal charge to ensure that you have the most stable possible structure (i.e. as many atoms having a formal charge as close to 0 as possible)