SiCl4 Lewis structure

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SiCl4 Lewis Structure
SiCl4 Lewis structure

SiCl4 (silicon tetrachloride) has one silicon atom and four chlorine atoms.

In the SiCl4 Lewis structure, there are four single bonds around the silicon atom, with four chlorine atoms attached to it, and on each chlorine atom, there are three lone pairs.


Use these steps to correctly draw the SiCl4 Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

  • First, determine the total number of valence electrons
Periodic table

In the periodic table, silicon lies in group 14, and chlorine lies in group 17.

Hence, silicon has four valence electrons and chlorine has seven valence electrons.

Since SiCl4 has one silicon atom and four chlorine atoms, so…

Valence electrons of one silicon atom = 4 × 1 = 4
Valence electrons of four chlorine atoms = 7 × 4 = 28

And the total valence electrons = 4 + 28 = 32

  • Second, find the total electron pairs

We have a total of 32 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 32 ÷ 2 = 16

  • Third, determine the central atom

We have to place the least electronegative atom at the center.

Since silicon is less electronegative than chlorine, assume that the central atom is silicon.

Therefore, place silicon in the center and chlorines on either side.

  • And finally, draw the rough sketch
SiCl4 Lewis Structure (Step 1)
Rough sketch of SiCl4 Lewis structure

#2 Mark lone pairs on the atoms

Here, we have a total of 16 electron pairs. And four Si — Cl bonds are already marked. So we have to only mark the remaining twelve electron pairs as lone pairs on the sketch.

Also remember that both (silicon and chlorine) are the period 3 elements, so they can keep more than 8 electrons in their last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are chlorines.

So for each chlorine, there are three lone pairs, and for silicon, there is zero lone pair because all twelve electron pairs are over.

Mark the lone pairs on the sketch as follows:

SiCl4 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of SiCl4

#3 Calculate and mark formal charges on the atoms, if required

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For silicon atom, formal charge = 4 – 0 – ½ (8) = 0

For each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, both silicon and chlorine atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (silicon) forms an octet. And the outside atoms (chlorines) also form an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable Lewis structure of SiCl4.

Next: BrO3 Lewis structure

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