Calculate the formal charges of the following: NH3, NO2- and NO3-. Thank you so much?

Answer 1

in NH3 , N is -3, each H is +1

in NO2- N is +3 each O is -2

in NO3- N is +5, each O is-2

Answer 2

Please specify the formal charge of what atom?
These answers are for the central atom (N). (Oxygen will have a FC of 0 or -1 in some cases)
Formal charge=> FC= group number - (number of bonds to atoms + number of lone pairs)
FC NH3 = V-(3+2)=0
NO2- does this mean connection 0-N-0 with one minus charge; then FC of N=0: V-(3+2)
NO3-; FC of N=+1; V-(4)

Answer 3

1. 0

2. -2

3. -5