Question

Assign formal charges to each atom in the resonance forms of n2o. which resonace form is likely to contribute most to the correct

Answer 1

Formal Charge is Calculated usinf following Formula,

Formal Charge  =  [# of Valence e⁻] - [# of Lone Pair e⁻ + 1/2 # of Bonding e⁻]

Lets calculate formal charge of Nitrogen in structure 3,

                              Formal Charge  =  [5] - [6 + 2/2]

                              Formal Charge  =  [5] - [6 + 1]

                              Formal Charge  =  [5] - [7]

                              Formal Charge  =  -2

You can calculate Formal charge for each atom in each resonating structure.
Also, the structure B dominates because the oxygen atom has a negative charge and being more electronegative in nature it is plausible.