Is PBr5 Polar or Nonpolar? (And Why?)

PBr5 is a NONPOLAR molecule.

But why? 

And how can you say that PBr5 is a nonpolar molecule?

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

PBr5 is a NONPOLAR molecule because all the five bonds (P-Br bonds) are identical and PBr5 has symmetrical geometry which cancels out the bond polarity.

Let me explain this in detail with the help of PBr5 lewis structure and its 3D geometry.

Why is PBr5 a Nonpolar molecule? (Explained in 3 Steps)

PBr5 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 PBr5 lewis structure and it contains five P-Br bonds.

(Note: If you want to know the steps of drawing the PBr5 lewis dot structure, then visit this article: PBr5 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the PBr5 molecule has five P-Br bonds.

Now in the next step we have to check whether these five P-Br 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] [5]}

Now let’s come to the example of PBr5 molecule. It has five P-Br bonds.

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

From the above image;

• Electronegativity of Phosphorus (P) = 2.19 ^[6]
• Electronegativity of Bromine (Br) = 2.96 ^[7]

Now let’s see the polarity of each bond.

For P-Br 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 Bromine (Br) is polar.
Hence, each P-Br 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 Bromine atoms (Br).

But wait, this alone won’t tell you whether the entire PBr5 molecule is polar or nonpolar.

So let’s proceed to the next step to check the symmetry of the PBr5 molecule.

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

Have a look at this 3D structure of PBr5. You can see that the structure of PBr5 is symmetrical. 

The phosphorus atom is at the center and it is surrounded by 5 bromine 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-Br) are symmetrical and the PBr5 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 PBr5.

Hence, the PBr5 molecule is a nonpolar molecule.

I hope you have understood the reason behind the nonpolar nature of PBr5 molecule.

See the polarity of other molecules to make your concepts clear:
Is SiO2 Polar or Nonpolar?
Is SBr2 Polar or Nonpolar?
Is CHF3 Polar or Nonpolar?
Is SeF4 Polar or Nonpolar?
Is CH2Br2 Polar or Nonpolar?