Is SiH4 Polar or Nonpolar? (And Why?)

SiH4 is a NONPOLAR molecule.

But why? 

And how can you say that SiH4 is a nonpolar molecule?

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

SiH4 is a NONPOLAR molecule because all the four bonds (Si-H bonds) are identical and SiH4 has symmetrical geometry.
Also the electronegativity difference of Silicon atom (Si = 1.9) and Hydrogen atom (H = 2.2) is 0.3 (i.e 2.2 – 1.9 = 0.3), which is very less. Hence the SiH4 molecule is a nonpolar molecule.

Let me explain this in detail with the help of SiH4 lewis structure and its 3D geometry.

Why is SiH4 a Nonpolar molecule? (Explained in 2 Steps)

SiH4 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 just 2 steps!

Step #1: Draw the lewis structure

Here is a skeleton of SiH4 lewis structure and it contains four Si-H bonds.

(Note: If you want to know the steps of drawing the SiH4 lewis dot structure, then visit this article: SiH4 lewis structure, Or you can also watch this short 2 minute video).

So from the above diagram we have come to know that the SiH4 molecule has four Si-H bonds.

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

And we also have to check the molecular geometry of SiH4.

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 SiH4 molecule. It has four Si-H bonds.

You can see the electronegativity values of Silicon (Si) and Hydrogen (H) atoms from the periodic table given below.

From the above image;

• Electronegativity of Silicon (Si) = 1.9 ^[6]
• Electronegativity of Hydrogen (H) = 2.2 ^[7]

Now let’s see the polarity of each bond.

For Si-H bond;
The electronegativity difference (ΔEN) = 2.2 – 1.9 = 0.3
This value is less than 0.4, which indicates that the bond between Silicon (Si) and Hydrogen (H) is nonpolar.
Hence, each Si-H bond is a nonpolar covalent bond.

As each Si-H bonds are nonpolar, there will not be any partial positive charge (ẟ+) or partial negative charge (ẟ-) on the silicon and hydrogen atoms.

From this, you can easily get the idea that the SiH4 molecule is a nonpolar molecule.

But let’s also see whether this SiH4 molecule has a symmetric geometry or not.

Have a look at this 3D structure of SiH4. You can see that the structure of SiH4 is symmetrical. 

The silicon atom is at the center and it is surrounded by 4 hydrogen atoms which are equidistant as well as at equal angles.

As all the four bonds (Si-H) are nonpolar and the SiH4 molecule has a symmetrical geometry, there are no positive and negative poles of charges on the overall molecule of SiH4.

Hence, the SiH4 molecule is a nonpolar molecule.

I hope you have understood the reason behind the nonpolar nature of SiH4 molecule.

See the polarity of other molecules to make your concepts clear:
Is Toluene (C6H5CH3) Polar or Nonpolar?
Is PBr5 Polar or Nonpolar?
Is SiO2 Polar or Nonpolar?
Is SBr2 Polar or Nonpolar?
Is CHF3 Polar or Nonpolar?