Is AlBr3 Polar or Nonpolar? (And Why?)

AlBr3 is a NONPOLAR molecule.

But why? 

And how can you say that AlBr3 is a nonpolar molecule?

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

AlBr3 is a NONPOLAR molecule because all the three bonds (Al-Br bonds) are identical and AlBr3 has symmetrical geometry which cancels out the bond polarity.

Let me explain this in detail with the help of AlBr3 lewis structure and its 3D geometry.

Why is AlBr3 a Nonpolar molecule? (Explained in 3 Steps)

AlBr3 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 AlBr3 lewis structure and it contains three Al-Br bonds.

(Note: If you want to know the steps of drawing the AlBr3 lewis dot structure, then visit this article: AlBr3 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the AlBr3 molecule has three Al-Br bonds.

Now in the next step we have to check whether these three Al-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 AlBr3 molecule. It has three Al-Br bonds.

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

From the above image;

• Electronegativity of Aluminum (Al) = 1.61 ^[6]
• Electronegativity of Bromine (Br) = 2.96 ^[7]

Now let’s see the polarity of each bond.

For Al-Br bond;
The electronegativity difference (ΔEN) = 2.96 – 1.61 = 1.35
This value lies between 0.4 to 1.7, which indicates that the bond between Aluminum (Al) and Bromine (Br) is polar.
Hence, each Al-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 Aluminum atom (Al) and partial negative charge (ẟ-) appears on the Bromine atoms (Br).

But wait, this alone won’t tell you whether the entire AlBr3 molecule is polar or nonpolar.

So let’s proceed to the next step to check the symmetry of the AlBr3 molecule.

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

Have a look at this 3D structure of AlBr3. You can see that the structure of AlBr3 is symmetrical. 

The aluminum atom is at the center and it is surrounded by 3 bromine atoms which are equidistant as well as at equal angles.

As all the three bonds (Al-Br) are symmetrical and the AlBr3 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 AlBr3.

Hence, the AlBr3 molecule is a nonpolar molecule.

I hope you have understood the reason behind the nonpolar nature of AlBr3 molecule.

See the polarity of other molecules to make your concepts clear:
Is KrF4 Polar or Nonpolar?
Is NBr3 Polar or Nonpolar?
Is SO2Cl2 Polar or Nonpolar?
Is SbF3 Polar or Nonpolar?
Is SeF2 Polar or Nonpolar?