PCl5 Lewis Structure in 5 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

PCl5 lewis structure has a Phosphorus atom (P) at the center which is surrounded by five Chlorine atoms (Cl). There are 5 single bonds between the Phosphorus atom (P) and each Chlorine atom (Cl).

If you haven’t understood anything from the above image of PCl5 (phosphorus pentachloride) lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of PCl5.

So let’s move to the steps of drawing the lewis structure of PCl5.

Steps of drawing PCl5 lewis structure

Step 1: Find the total valence electrons in PCl5 molecule

In order to find the total valence electrons in PCl5 (phosphorus pentachloride) molecule, first of all you should know the valence electrons present in phosphorus atom as well as chlorine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of phosphorus as well as chlorine using a periodic table.

Total valence electrons in PCl5 molecule

→ Valence electrons given by phosphorus atom:

Phosphorus is group 15 element on the periodic table. ^[1] Hence the valence electrons present in phosphorus is 5.

You can see the 5 valence electrons present in the phosphorus atom as shown in the above image.

→ Valence electrons given by chlorine atom:

Chlorine is group 17 element on the periodic table. ^[2] Hence the valence electrons present in chlorine is 7.

You can see the 7 valence electrons present in the chlorine atom as shown in the above image.

Hence, 

Total valence electrons in PCl5 molecule = valence electrons given by 1 phosphorus atom + valence electrons given by 5 chlorine atoms = 5 + 7(5) = 40.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

Now here the given molecule is PCl5 (phosphorus pentachloride) and it contains phosphorus atom (P) and chlorine atoms (Cl).

You can see the electronegativity values of phosphorus atom (P) and chlorine atom (Cl) in the above periodic table.

If we compare the electronegativity values of phosphorus (P) and chlorine (Cl) then the phosphorus atom is less electronegative.

So here the phosphorus atom (P) is the center atom and the chlorine atoms (Cl) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the PCl5 molecule, you have to put the electron pairs between the phosphorus atom (P) and chlorine atoms (Cl).

This indicates that the phosphorus (P) and chlorine (Cl) are chemically bonded with each other in a PCl5 molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of PCl5 molecule, you can see that the outer atoms are chlorine atoms.

These outer chlorine atoms are forming an octet and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the PCl5 molecule.

The PCl5 molecule has a total 40 valence electrons and all these valence electrons are used in the above sketch of PCl5.

Hence there are no remaining electron pairs to be kept on the central atom. 

So now let’s proceed to the next step.

Step 5: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of PCl5.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on phosphorus (P) atom as well as chlorine (Cl) atoms present in the PCl5 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of PCl5 molecule in the image given below.

For Phosphorus (P) atom:
Valence electrons = 5 (because phosphorus is in group 15)
Bonding electrons = 10
Nonbonding electrons = 0

For Chlorine (Cl) atom:
Valence electrons = 7 (because chlorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
P	=	5	–	10/2	–	0	=	0
Cl	=	7	–	2/2	–	6	=	0

From the above calculations of formal charge, you can see that the phosphorus (P) atom as well as chlorine (Cl) atom has a “zero” formal charge.

This indicates that the above lewis structure of PCl5 is stable and there is no further change in the above structure of PCl5.

In the above lewis dot structure of PCl5, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of PCl5.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

H2O2 lewis structure	F2 lewis structure
CH2Cl2 lewis structure	ClO2- lewis structure
ClO3- lewis structure	HCl lewis structure