Lewis Structure of SiH2Cl2 (With 6 Simple Steps to Draw!)

I’m super excited to teach you the lewis structure of SiH2Cl2 in just 6 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of SiH2Cl2 molecule.

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of SiH2Cl2 contains a single bond between the Silicon (Si) & Hydrogen (H) atoms as well as between the Silicon (Si) & Chlorine (Cl) atoms. The Silicon atom (Si) is at the center and it is surrounded by two Hydrogen (H) and two Chlorine atoms (Cl). Both the Chlorine atoms have 3 lone pairs.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of SiH2Cl2).

6 Steps to Draw the Lewis Structure of SiH2Cl2

Step #1: Calculate the total number of valence electrons

Here, the given molecule is SiH2Cl2. In order to draw the lewis structure of SiH2Cl2, first of all you have to find the total number of valence electrons present in the SiH2Cl2 molecule.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in SiH2Cl2

• For Silicon: 

Silicon is a group 14 element on the periodic table. ^[1]

Hence, the valence electrons present in silicon is 4 (see below image).

• For Hydrogen: 

Hydrogen is a group 1 element on the periodic table. ^[2]

Hence, the valence electron present in hydrogen is 1 (see below image).

• For Chlorine:

Chlorine is a group 17 element on the periodic table. ^[3]

Hence, the valence electron present in chlorine is 7 (see below image).

Hence in a SiH2Cl2 molecule, 

Valence electrons given by Silicon (Si) atom = 4
Valence electron given by each Hydrogen (H) atom = 1
Valence electrons given by each Chlorine (Cl) atom = 7
So, total number of Valence electrons in SiH2Cl2 molecule = 4 + 1(2) + 7(2) = 20

Step #2: Select the center atom (H is always outside)

While selecting the center atom, always put the least electronegative atom at the center.

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[4]

Here in the SiH2Cl2 molecule, if we compare the silicon atom (Si) and chlorine atom (Cl), then the silicon is less electronegative than chlorine.

So, silicon should be placed in the center and the chlorine atom will surround it.

Also as per the rule, we have to keep hydrogen outside.

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of SiH2Cl2 molecule, put the two electrons (i.e electron pair) between the silicon-hydrogen atoms and silicon-chlorine atoms to represent a chemical bond between them.

These pairs of electrons present between the Silicon & Chlorine atoms as well as between the Silicon & Hydrogen atoms form a chemical bond, which bonds these atoms with each other in a SiH2Cl2 molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of SiH2Cl2, the outer atoms are hydrogen atoms and chlorine atoms.

So now, you have to check whether these hydrogen atoms are forming a duplet or not! (because hydrogen requires only 2 electrons to have a complete outer shell).

You also have to see whether the chlorine atoms are forming an octet or not! (because chlorine requires 8 electrons to have a complete outer shell).

You can see in the above image that both the hydrogen atoms form a duplet. And the chlorine atoms also form an octet.

Also, all the 20 valence electrons of SiH2Cl2 molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of SiH2Cl2.

Let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

In this step, we have to check whether the central atom (i.e silicon) has an octet or not. 

In simple words, we have to check whether the central Silicon (Si) atom is having 8 electrons or not.

As you can see from the above image, the central atom (i.e silicon), is having 8 electrons. So it fulfills the octet rule and the silicon atom is stable.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on silicon atom (Si), chlorine (Cl) atoms as well as hydrogen atoms (H).

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

• For Silicon:
  Valence electrons = 4 (as it is in group 14)
  Nonbonding electrons = 0
  Bonding electrons = 8
• For Chlorine:
  Valence electron = 7 (as it is in group 17)
  Nonbonding electrons = 6
  Bonding electrons = 2
• For Hydrogen:
  Valence electron = 1 (as it is in group 1)
  Nonbonding electrons = 0
  Bonding electrons = 2

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
Si	=	4	–	0	–	8/2	=	0
Cl	=	7	–	6	–	2/2	=	0
H	=	1	–	0	–	2/2	=	0

So you can see above that the formal charges on silicon, chlorine as well as hydrogen are “zero”.

Hence, there will not be any change in the above structure and the above lewis structure of SiH2Cl2 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of SiH2Cl2 represents the single bond ( | ). So the above lewis dot structure of SiH2Cl2 can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of NF5
Lewis Structure of SiO
Lewis Structure of AlI3
Lewis Structure of PF2-
Lewis Structure of SI4 

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