Is AlCl3 Polar or Nonpolar? (And Why?)

AlCl3 is a NONPOLAR molecule.

But why? 

And how can you say that AlCl3 is a nonpolar molecule?

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

AlCl3 is a NONPOLAR molecule because all the three bonds (Al-Cl bonds) are identical and AlCl3 has symmetrical geometry which cancels out the bond polarity.

Let me explain this in detail with the help of AlCl3 lewis structure and its 3D geometry.

Why is AlCl3 a Nonpolar molecule? (Explained in 3 Steps)

AlCl3 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 AlCl3 lewis structure and it contains three Al-Cl bonds.

(Note: If you want to know the steps of drawing the AlCl3 lewis dot structure, then visit this article: AlCl3 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the AlCl3 molecule has three Al-Cl bonds.

Now in the next step we have to check whether these three Al-Cl 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 AlCl3 molecule. It has three Al-Cl bonds.

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

From the above image;

• Electronegativity of Aluminum (Al) = 1.61 ^[6]
• Electronegativity of Chlorine (Cl) = 3.16 ^[7]

Now let’s see the polarity of each bond.

For Al-Cl bond;
The electronegativity difference (ΔEN) = 3.16 – 1.61 = 1.55
This value lies between 0.4 to 1.7, which indicates that the bond between Aluminum (Al) and Chlorine (Cl) is polar.
Hence, each Al-Cl 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 Chlorine atoms (Cl).

But wait, this alone won’t tell you whether the entire AlCl3 molecule is polar or nonpolar.

So let’s proceed to the next step to check the symmetry of the AlCl3 molecule.

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

Have a look at this 3D structure of AlCl3. You can see that the structure of AlCl3 is symmetrical. 

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

As all the three bonds (Al-Cl) are symmetrical and the AlCl3 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 AlCl3.

Hence, the AlCl3 molecule is a nonpolar molecule.

I hope you have understood the reason behind the nonpolar nature of AlCl3 molecule.

See the polarity of other molecules to make your concepts clear:
Is COCl2 Polar or Nonpolar?
Is C3H8 (Propane) Polar or Nonpolar?
Is SiBr4 Polar or Nonpolar?
Is CHBr3 Polar or Nonpolar?
Is ICl4- Polar or Nonpolar?