# Formal charge on these two atoms

1. Dec 2, 2012

### wahaj

1. The problem statement, all variables and given/known data

find formal charge on P in PBr3 and N in NBrI2

2. Relevant equations

Formal charge = number of valence electrons-number of lone pairs- 1/2 number of bonding electrons

3. The attempt at a solution

FC on P = 5 - 1 - 3 = 1
FC on N = 5 - 1 - 3 = 1

these are wrong for some reason and I can't figure out. I know I have the lewis diagram correct for these molecules(I checked)

2. Dec 9, 2012

### chemisttree

How does the Lewis diagram help you here? I always calculated what I knew first and then balanced the molecule's charge by assigning the oxidation number of the unknown. In these examples, I would have assumed the halogens were -1 as you have and the P or N would have an equal but opposite charge.

3. Dec 10, 2012

### symbolipoint

NBrI2

Halides usually have charge of -1. The compound given is as neutral charge.
N, u
Br, -1
I, -1
I, -1
Total, 0.

Find u.

4. Dec 21, 2012

### Vineeth T

The formal charges in both the cases is zero.
In your above formula for FC you wrote the second term as " number of electron pairs ",it should be " number of non-bonded electrons ".

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