Is IBr3 Polar or Nonpolar? (And Why?)

IBr3 is a POLAR molecule.

But why? 

And how can you say that IBr3 is a polar molecule?

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

IBr3 is a POLAR molecule because it has two lone pairs of electrons on the Iodine atom (I) which causes the entire molecule to bend.
This bending of IBr3 molecule results in asymmetric geometry, which makes the molecule polar.

Let me explain this in detail with the help of IBr3 lewis structure and its 3D geometry.

Why is IBr3 a Polar molecule? (Explained in 2 Steps)

To understand the polar nature of IBr3 molecule, first of all you should know its lewis structure as well as its molecular geometry.

So let’s see this in the steps below.

Step #1: Draw the lewis structure

Here is a skeleton of IBr3 lewis structure and it contains three I-Br bonds.

(Note: If you want to know the steps of drawing the IBr3 lewis dot structure, then visit this article: IBr3 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the IBr3 molecule has three I-Br bonds.

Now in the next step we have to check whether these three I-Br bonds are polar or nonpolar.

And we also have to check the molecular geometry of IBr3.

Step #2: Check the bond polarity and molecular geometry

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 IBr3 molecule. It has three I-Br bonds.

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

From the above image;

• Electronegativity of Iodine (I) = 2.66 ^[6]
• Electronegativity of Bromine (Br) = 2.96 ^[7]

Now let’s see the polarity of each bond.

For I-Br bond;
The electronegativity difference (ΔEN) = 2.96 – 2.66 = 0.3
This value is less than 0.4, which indicates that the bond between Iodine (I) and Bromine (Br) is nonpolar.
Hence, each I-Br bond is a nonpolar covalent bond.

But wait, we also have to look at the molecular geometry of IBr3 to know whether it has a symmetric shape or not.

Have a look at this 3D structure of IBr3. The Iodine atom (I) is at the center and it is surrounded by 3 Bromine atoms (Br).

It also has two lone pairs on the Iodine atom (I).

Due to the lone pairs on the iodine atom (I), its molecular geometry becomes asymmetric.

Because of this, there are positive and negative poles of charges on the overall molecule of IBr3.

Hence, the IBr3 molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of IBr3 molecule.

See the polarity of other molecules to make your concepts clear:
Is NH2- Polar or Nonpolar?
Is KrF2 Polar or Nonpolar?
Is BrCl5 Polar or Nonpolar?
Is ClO2- Polar or Nonpolar?
Is XeCl4 Polar or Nonpolar?