Is NOBr Polar or Nonpolar? (And Why?)

NOBr is a POLAR molecule.

But why? 

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

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

NOBr is a POLAR molecule because it has a lone pair of electrons on the Nitrogen atom (N) which causes the entire molecule to bend.
This bending of NOBr molecule results in asymmetric geometry, which makes the molecule polar.

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

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

To understand the polar nature of NOBr 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 NOBr lewis structure and it contains one N=O bond and one N-Br bond.

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

So from the above diagram we have come to know that the NOBr molecule has one N=O and one N-Br bond.

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

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

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 NOBr molecule. It has N=O bond and N-Br bond.

You can see the electronegativity values of Nitrogen (N), Oxygen (O) and Bromine (Br) atoms from the periodic table given below.

From the above image;

• Electronegativity of Nitrogen (N) = 3.04 ^[6]
• Electronegativity of Oxygen (O) = 3.44 ^[7]
• Electronegativity of Bromine (Br) = 2.96 ^[8]

Now let’s see the polarity of each bond.

For Nitrogen-Oxygen bond;
The electronegativity difference (ΔEN) = 3.44 – 3.04 = 0.4
Now this value is exactly between the range of polar and nonpolar bonds, so we cannot perfectly say whether the Nitrogen-Oxygen bonds are polar or nonpolar.
In some textbooks, you may find some different range of ΔEN, but if we consider the above mentioned range for ΔEN, then we can say that the Nitrogen-Oxygen bonds can be either highly nonpolar or very less polar.

For N-Br bond;
The electronegativity difference (ΔEN) = 3.04 – 2.96 = 0.08 
This value is less than 0.4, which indicates that the bond between Nitrogen (N) and Bromine (Br) is nonpolar.
Hence, the N-Br bond is a nonpolar covalent bond.

But let’s keep this discussion aside.

Because we also have to look at the molecular geometry of NOBr to know whether it has a symmetric shape or not.

Have a look at this 3D structure of NOBr. The Nitrogen atom (N) is at the center and it is surrounded by Oxygen atom (O) and Bromine atom (Br).

It also has one lone pair on the Nitrogen atom (N).

Due to the lone pair on the nitrogen atom (N), its molecular geometry becomes asymmetric.

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

Hence, the NOBr molecule is a polar molecule.

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

See the polarity of other molecules to make your concepts clear:
Is GeH4 Polar or Nonpolar?
Is Isopropanol (C3H8O) Polar or Nonpolar?
Is Butane (C4H10) Polar or Nonpolar?
Is CN- Polar or Nonpolar?
Is N2H4 Polar or Nonpolar?