Is SF4 Polar or Nonpolar? (And Why?)

SF4 is a POLAR molecule.

But why? 

And how can you say that SF4 is a polar molecule?

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

SF4 is a POLAR molecule because the Fluorine (F) present in the molecule is more electronegative, 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 SF4 molecule polar.

Let me explain this in detail with the help of SF4 lewis structure and its 3D geometry.

Why is SF4 a Polar molecule? (Explained in 3 Steps)

SF4 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 3 steps!

Step #1: Draw the lewis structure

Here is a skeleton of SF4 lewis structure and it contains four S-F bonds.

(Note: If you want to know the steps of drawing the SF4 lewis dot structure, then visit this article: SF4 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the SF4 molecule has four S-F bonds.

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

And we also have to check the molecular geometry of SF4.

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 SF4 molecule. It has four S-F bonds.

You can see the electronegativity values of Sulfur (S) and Fluorine (F) atoms from the periodic table given below.

From the above image;

• Electronegativity of Sulfur (S) = 2.58 ^[6]
• Electronegativity of Fluorine (F) = 3.98 ^[7]

Now let’s see the polarity of each bond.

For S-F bond;
The electronegativity difference (ΔEN) = 3.98 – 2.58 = 1.4
This value lies between 0.4 to 1.7, which indicates that the bond between Sulfur (S) and Fluorine (F) is polar.
Hence, the S-F bond is a polar covalent bond.

You can see in the above image that because of higher electronegativity of Fluorine atom, the partial positive charge (ẟ+) appears on the Sulfur atoms (S) and partial negative charge (ẟ-) appears on the Fluorine atom (F).

But wait, we also have to look at the molecular geometry of SF4 to know whether it has a symmetric shape or not.

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

Have a look at this 3D structure of SF4. The Sulfur atom (S) is at the center and it is surrounded by 4 Fluorine atoms (F).

It also has one lone pair on the Sulfur atom (S).

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

Because of this, there are positive and negative poles of charges on the overall molecule of SF4.

Hence, the SF4 molecule is a polar molecule.

I hope you have understood the reason behind the polar nature of SF4 molecule.

See the polarity of other molecules to make your concepts clear:
Is SO3 Polar or Nonpolar?
Is PCl3 Polar or Nonpolar?
Is HCN Polar or Nonpolar?
Is CH2O Polar or Nonpolar?
Is XeF4 Polar or Nonpolar?