## Formal Charge Calculation

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

Baoying Li 1B
Posts: 113
Joined: Sat Aug 17, 2019 12:18 am

### Formal Charge Calculation

Hey guys, can someone explain the process of assigning formal charges in detail? What is it mean to count the bonding? Why is the resonance the most stable when Fc equals to 0?

Camellia Liu 1J
Posts: 51
Joined: Sat Aug 24, 2019 12:15 am

### Re: Formal Charge Calculation

Formal charge indicates the gain or the loss of electrons of an atom in the formation of a covalent bond.

To assign formal charge:
Formal Charge = V - (L + ½ S)
where V is the number of valence electrons in the free atom
L is the number of electrons present on the bonded atom as lone pairs
and S is the number of bonding/ shared electrons on the atom

When there is a low formal charge, it means that an atom has undergone only a small redistribution of electrons relative to the free atom

LNgo 1G
Posts: 100
Joined: Sat Aug 24, 2019 12:16 am

### Re: Formal Charge Calculation

The resonance form with the most formal charges equal to zero means that there is a more equal sharing of electrons since there are no partial charges on the atom(s).

Micah3J
Posts: 100
Joined: Tue Oct 08, 2019 12:16 am

### Re: Formal Charge Calculation

When calculating the formal charge, we want the outer elements to carry the negative charge as opposed to the middle element right? If so, can someone explain why?

Chantel_2I
Posts: 109
Joined: Sat Sep 07, 2019 12:19 am

### Re: Formal Charge Calculation

Micah3J wrote:When calculating the formal charge, we want the outer elements to carry the negative charge as opposed to the middle element right? If so, can someone explain why?

The element with the lowest ionization energy goes in the middle, which means the middle one is less electronegative than the outer ones. Since the outer atoms are more electronegative, they would be more stable with a negative charge than the middle atom would be because they more strongly attract electrons.