Step 1: Find valence e- for all atoms. Add them together.
Step2: Find octet e- for each atom and add them together.
Step3: Gives you bonding e-. Subtract step 1 total from step 2
Step 4: Find number of bonds by diving the number in step 3 by 2(because each bond is made of 2 e-)
66e-/2= 33 bond pairs
Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.
78-66= 12e-=6 lone pair
This molecule is a complex molecule and there are multiple central atoms.You can not draw lewis structure unless you know the predetermined structure of tryptophan.
Lone pairs are in green. Bond pairs are in purple.