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### Formal Charge of Ions

Posted: Mon Oct 29, 2018 10:51 pm
For an ion, for example SO4 2-, do you want the overall formal charge to be zero or 2-? I'm confused because I remember Dr. Lavelle mentioning that compounds are most stable with a formal charge of zero, but I also remember something about how you have to maintain the charge of the ion.

### Re: Formal Charge of Ions

Posted: Mon Oct 29, 2018 11:06 pm
I think Dr. Lavelle meant for the central atom of sulfur to have a formal charge of 0, but the overall formal charge to stay at 2-. For sulfur here, with 6 valence electrons, in the formula FC = V - (l + s/2), FC = 6-(0 +12/2), FC=0.

### Re: Formal Charge of Ions

Posted: Tue Oct 30, 2018 6:49 pm
The overall charge of the sulfate ion is 2-, but the central atom sulfur has a formal charge of 0 based on the FC = V - (L +S/2) formula.

### Re: Formal Charge of Ions

Posted: Tue Oct 30, 2018 6:53 pm
Why would the central charge be different from the overall charge of the molecule? I'm having a difficult time understanding this concept

### Re: Formal Charge of Ions

Posted: Thu Nov 01, 2018 9:19 pm
Would you have to draw all the resonance structures of an ion/compound/etc. in order to determine the formal charge?

### Re: Formal Charge of Ions

Posted: Thu Nov 01, 2018 9:37 pm
I think the central charge only contributes to the overall net charge of the atom, so as long as the charge of the central atom in addition to the other atoms equal the overall charge, it'll be fine because that's what you're looking for.

### Re: Formal Charge of Ions

Posted: Fri Nov 02, 2018 10:07 am
I believe if you add up all the formal charges, you get the charge of the overall compound/ion. Each individual atom can have a different charge

### Re: Formal Charge of Ions

Posted: Fri Nov 02, 2018 10:18 am
Unless the question states that it wants the resonance structure drawn, then technically you would not have to draw it to determine formal charge because you could just use the formula; however, is extremely helpful to draw it out to make sure you have the correct number of lone pair and shared electrons.

### Re: Formal Charge of Ions

Posted: Fri Nov 02, 2018 11:12 am
When it comes to formal charge your goal is for it to be zero (or closest to zero) because it represents the stability of the specific atom. That is why you take the formal charge of each atom present in your compound, to see if they are all formally charged to 0.

### Re: Formal Charge of Ions

Posted: Fri Nov 02, 2018 1:43 pm
You want each individual atom to be as close to zero as possible, but the overall formal charges should add up to the charge of the molecule.