Is PCl5 Polar or Nonpolar? (And Why?)

PCl5 is a NONPOLAR molecule.

But why? 

And how can you say that PCl5 is a nonpolar molecule?

Want to know the reason?
Let’s dive into it!

PCl5 is a NONPOLAR molecule because all the five bonds (P-Cl bonds) are identical and PCl5 has symmetrical geometry which cancels out the bond polarity.

Let me explain this in detail with the help of PCl5 lewis structure and its 3D geometry.

Why is PCl5 a Nonpolar molecule? (Explained in 3 Steps)

PCl5 is a nonpolar molecule because it does not have any pole of positive charge and negative charge on it.

Let me explain this to you in 3 steps!

Step #1: Draw the lewis structure

Here is a skeleton of PCl5 lewis structure and it contains five P-Cl bonds.

(Note: If you want to know the steps of drawing the PCl5 lewis dot structure, then visit this article: PCl5 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the PCl5 molecule has five P-Cl bonds.

Now in the next step we have to check whether these five P-Cl bonds are polar or nonpolar.

Step #2: Check whether individual bonds are polar or nonpolar

The chemical bonds can be either nonpolar, polar or ionic depending on the difference of the electronegativity values (ΔEN) between the two atoms.

Have a look at the above image.

• If the electronegativity difference (ΔEN) is less than 0.4, then the bond is nonpolar covalent bond.
• If the electronegativity difference (ΔEN) is between 0.4 to 1.7, then the bond is polar covalent bond. 
• If the electronegativity difference (ΔEN) is greater than 1.7, then the bond is an ionic bond. ^{[1] [2] [3] [4]}

Now let’s come to the example of PCl5 molecule. It has five P-Cl bonds.

You can see the electronegativity values of Phosphorus (P) and Chlorine (Cl) atoms from the periodic table given below.

From the above image;

• Electronegativity of Phosphorus (P) = 2.19 ^[5]
• Electronegativity of Chlorine (Cl) = 3.16 ^[6]

Now let’s see the polarity of each bond.

For P-Cl bond;
The electronegativity difference (ΔEN) = 3.16 – 2.19 = 0.97
This value lies between 0.4 to 1.7, which indicates that the bond between Phosphorus (P) and Chlorine (Cl) is polar.
Hence, each P-Cl bond is a polar covalent bond.

You can see in the above image that because of electronegativity difference, the partial positive charge (ẟ+) appears on the Phosphorus atom (P) and partial negative charge (ẟ-) appears on the Chlorine atoms (Cl).

But wait, this alone won’t tell you whether the entire PCl5 molecule is polar or nonpolar.

So let’s proceed to the next step to check the symmetry of the PCl5 molecule.

Step #3: Check whether the molecule is symmetric or not

Have a look at this 3D structure of PCl5. You can see that the structure of PCl5 is symmetrical. 

The phosphorus atom is at the center and it is surrounded by 5 chlorine atoms which are equidistant as well as at equal angles (The 2 axial bonds are identical as well as remaining 3 equatorial bonds are identical).

As all the five bonds (P-Cl) are symmetrical and the PCl5 molecule has a symmetrical geometry, their bond polarity gets canceled with each other.

Because of this, there are no positive and negative poles of charges on the overall molecule of PCl5.

Hence, the PCl5 molecule is a nonpolar molecule.

I hope you have understood the reason behind the nonpolar nature of PCl5 molecule.

See the polarity of other molecules to make your concepts clear:
Is Cl2 Polar or Nonpolar?
Is HBr Polar or Nonpolar?
Is H2 Polar or Nonpolar?
Is CBr4 Polar or Nonpolar?
Is OF2 Polar or Nonpolar?