Is CH3Br Polar or Nonpolar? (And Why?)

CH3Br is a POLAR molecule.

But why? 

And how can you say that CH3Br is a polar molecule?

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

CH3Br is a POLAR molecule because the C-Br bond present in the molecule is polar, which causes the partial positive (ẟ+) and partial negative (ẟ-) charge to appear on the molecule. These ẟ+ and ẟ- charges are responsible to make the entire CH3Br molecule polar.

Let me explain this in detail with the help of CH3Br lewis structure and its 3D geometry.

Why is CH3Br a Polar molecule? (Explained in 2 Steps)

CH3Br is a polar molecule because it has poles of partial positive charge (ẟ+) and partial negative charge (ẟ-) on it.

Let me explain this to you in 2 steps!

Step #1: Draw the lewis structure

Here is a skeleton of CH3Br lewis structure and it contains three C-H bonds and one C-Br bond.

(Note: If you want to know the steps of drawing the CH3Br lewis dot structure, then visit this article: CH3Br lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the CH3Br molecule has three C-H bonds and one C-Br bond.

Now in the next step we have to check whether these three C-H bonds and one C-Br bond are polar or nonpolar.

And we also have to check the molecular geometry of CH3Br.

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]}

Now let’s come to the example of CH3Br molecule. It has three C-H bonds and one C-Br bond.

You can see the electronegativity values of Carbon (C), Hydrogen (H) and Bromine (Br) atoms from the periodic table given below.

From the above image;

• Electronegativity of Carbon (C) = 2.55 ^[5]
• Electronegativity of Hydrogen (H) = 2.2 ^[6]
• Electronegativity of Bromine (Br) = 2.96 ^[7]

Now let’s see the polarity of each bond.

For C-H bond;
The electronegativity difference (ΔEN) = 2.55 – 2.2 = 0.35 
This value is less than 0.4, which indicates that the bond between Carbon (C) and Hydrogen (H) is nonpolar.
Hence, each C-H bond is a nonpolar covalent bond.

For C-Br bond;
The electronegativity difference (ΔEN) = 2.96 – 2.55 = 0.41
This value lies between 0.4 to 1.7, which indicates that the bond between Carbon (C) and Bromine (Br) is polar.
Hence, the C-Br bond is a polar covalent bond.

You can see in the above image that because of large electronegativity difference of Carbon and Bromine atom, the partial positive charge (ẟ+) appears on the Carbon atom (C) and partial negative charge (ẟ-) appears on the Bromine atom (Br).

From this, you can easily get the idea that the CH3Br molecule is a polar molecule.

But let’s also see its 3D molecular geometry for better understanding.

Have a look at this 3D structure of CH3Br. The more electronegative bromine atom (Br) has a tendency to pull the shared electron pair towards itself, which results in partial positive charge on carbon atom (C) and partial negative charge on bromine atom (Br).

Because of this, there are positive and negative poles of charges on the overall molecule of CH3Br.

Hence, the CH3Br molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of CH3Br molecule.

See the polarity of other molecules to make your concepts clear:
Is PBr3 Polar or Nonpolar?
Is CF2Cl2 Polar or Nonpolar?
Is C2H6 Polar or Nonpolar?
Is OCl2 Polar or Nonpolar?
Is OCS Polar or Nonpolar?