Step 1: Find valence e- for all atoms. Add them together.
Step2: Find octet e- for each atom and add them together.
Phosphorous gets 10 electrons since it should make 5 bonds with surrounding atoms.
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-)
10e-/2= 5 bond pairs
Step 5: Find the number of nonbonding (lone pairs) e-. Subtract step 3 number from step 1.
40-10= 30e-=15 lone pairs
Use information from step 4 and 5 to draw the lewis structure.
Lewis dot structure of PCl5
Alternatively a dot method can be used to draw the lewis structure.
Calculate the total valence electrons in the molecule.
Put put phosphorous in center and chlorines on sides.
Put a pair of electrons connecting the side atom with central atom.Put remaining electrons on the side atoms.