A visual representation of covalent bonding which represents the valence shell electrons in the molecule is said to be a Lewis structure. The lines represents the shared electron pairs and dots represents the electrons that are not involved in the bonding i.e lone pairs.
Number of valence electrons in each atom:
For Carbon, = 4
For Hydrogen, = 1
For Nitrogen, = 5
The Lewis structure of is shown in the attached image.
The formula of calculating formula charge = -(1)
where, F.C is formal charge, V.E is number of valence electrons, N.E is number of non-bonding electrons and B.E is number of bonding electrons.
Now, calculating the formal charge:
For on left side:
For :
For on right side:
The formula charge of each atom other than hydrogen is shown in the attached image.