Formal Charge Placement

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

Ashley Kao 1H
Posts: 50
Joined: Thu Jul 25, 2019 12:16 am

Formal Charge Placement

We learned that in a bond with a negative charge, the negative formal charge will be located at the most electronegative atom, but what about a positive charge? Does the placement of a positive formal charge matter?

kevinchang_4I
Posts: 55
Joined: Tue Nov 13, 2018 12:17 am

Re: Formal Charge Placement

It usually does matter in the same way we apply negative formal charges. Because we try to apply neg charges to the most electronegative atom, we try to apply pos charges to the least electronegative atom. This is usually the central atom. However, making our formal charges zero is still the primary goal.

Jielena_Bragasin2G
Posts: 104
Joined: Sat Aug 24, 2019 12:18 am
Been upvoted: 1 time

Re: Formal Charge Placement

Usually it is put on the most electropositive atom, hence it usually being on the central atom. However, like the comment said before, it is not as important as where a spare electron is placed. Hope this helps!

Manav Govil 1B
Posts: 104
Joined: Sat Sep 07, 2019 12:19 am

Re: Formal Charge Placement

Negative charges tend to be put on the more electronegative atom, while the positive charge is put on the atom affected by the electronegative atom.

Look at SO2. There is a negative charge on the Oxygen (the more electronegative atom), and a positive charge on Sulfur (the element affected by the electronegativity of Oxygen).

There are exceptions, such as CO, where the positive charge is on the Oxygen, and the negative charge is on the Carbon. This tells us that the octet rule takes priority over formal charges.

305385703
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am

Re: Formal Charge Placement

The positive charge will depend on where the negative charges are. Octet rules are obeyed first, then electronegativity and lowest formal charge should be obeyed, and then the positive charges will be in the places that they should be. It's not a matter of placing the positive charges where they should be, it's about putting the lowest formal charges on the most electronegative atoms first.