Step 1: Find valence e- for all atoms. Add them together.
N:5
O:6
Cl:7
Total=18
Step2: Find octet e- for each atom and add them together.
C:8
O:8
Cl:8
Total=24
Step3: Gives you bonding e-. Subtract step 1 total from step 2
24-18=6e-
Step 4: Find number of bonds by diving the number in step 3 by 2(because each bond is made of 2 e-)
6e-/2= 3 bond pairs
Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.
18-6= 12e-=6 lone pairs
Use information from step 4 and 5 to draw the lewis structure.
According to electronegativity rule, Nitrogen has the least EN and needs three bonds to gain octet.So put nitrogen in the centre.
Alternatively a dot method can be used to draw the lewis structure.
Calculate the total valence electrons in the molecule.
N:5
O:6
Cl:7
Total=18
Put nitrogen in center and arrange oxygen and chlorine atoms on the sides.Arrange electrons until all elements get 8 electrons.