Formal charge with ions

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

Lily Emerson 1I
Posts: 27
Joined: Fri Apr 06, 2018 11:02 am

Formal charge with ions

when calculating formal charges of ions, do we add/subtract the indicated charges on the atoms that they influence? or do we just use the typical number of valence electrons?

Tiffany Chen 1A
Posts: 36
Joined: Fri Apr 06, 2018 11:02 am
Been upvoted: 1 time

Re: Formal charge with ions

To calculate the formal charges of atoms in a molecule, you use the typical number of valence electrons for that atom. But if you added the formal charges of all the atoms in an ion, they should add up to the total charge of the ion.

For example, in CH3(-), C has a formal charge of -1 (FC=4-2-3=-1) and all of the H atoms have a formal charge of 0. Adding -1+0+0+0 = -1, which is the total charge of the ion.

Patience Olsen 1A
Posts: 28
Joined: Fri Apr 06, 2018 11:04 am

Re: Formal charge with ions

The last answer explains it well. The charge of the ion should be the same as the formal charge. This is why the formal charges of atoms and molecules should be equal to 0 if they are not ionized.

Harmonie Ahuna-1C
Posts: 30
Joined: Fri Apr 06, 2018 11:01 am

Re: Formal charge with ions

You calculate it the same as you would if there were no charge, and should get the overall charge of the ion when adding up the formal charges of each atom.