Lewis structure of SiS2

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The Lewis structure of SiS₂ contains two double bonds, with silicon in the center, and two sulfurs on either side. There are two lone pairs on each sulfur atom, and the silicon atom does not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of SiS₂.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… silicon is a group 14 element and sulfur is a group 16 element. Hence, silicon has four valence electrons and sulfur has six valence electrons.

Now SiS₂ has one silicon atom and two sulfur atoms.

So the total number of valence electrons = valence electrons of silicon atom + (valence electrons of sulfur atom × 2)

Therefore, the total number of valence electrons = 4 + 12 = 16

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for silicon and sulfur as follows:

Electronegativity value of silicon = 1.90
Electronegativity value of sulfur = 2.58

Obviously, silicon is less electronegative than sulfur. Hence, assume that silicon is the central atom.

So now, put silicon in the center and sulfurs on either side. And draw the rough skeleton structure for the Lewis structure of SiS₂ something like this:

Also read: How to draw Lewis structure of PBr₅ (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since silicon is surrounded by two sulfurs, use four electrons to show two chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 16 valence electrons. And in the above structure, we have already used four valence electrons. Hence, twelve valence electrons are remaining.

Two valence electrons represent one lone pair. So twelve valence electrons = six lone pairs.

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

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are sulfurs, so each sulfur will get three lone pairs. And the central atom (silicon) will not get any lone pair, because all six lone pairs are used.

So the Lewis structure of SiS₂ looks something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (silicon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of OCS (5 steps)

#4 Complete octet on central atom

Remember that silicon is a period 3 element, so it can keep more than 8 electrons in its last shell.

Now silicon already has four valence electrons. Hence, silicon needs four more valence electrons to complete its octet.

So convert one lone pair from each sulfur atom to make a new bond with the silicon atom. And then, the Lewis structure of SiS₂ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (silicon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of H₃O⁺ (4 steps)

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For silicon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For each sulfur atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of SiS₂ looks something like this:

In the above structure, you can see that the formal charges of both (silicon and sulfur) are zero. Therefore, this is the stable Lewis structure of SiS₂.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of PBr₅
• Lewis structure of OCS
• Lewis structure of H₃O⁺
• Lewis structure of AsH₃
• Lewis structure of Br₃^–

External links

• SiS2 Lewis Structure in 6 Steps (With Images) – Pediabay
• SiS2 Lewis Structure, Hybridization, Molecular Geometry, and Bond Angles – Geometry of Molecules
• SiS2 Lewis Structure, Molecular Geometry, Hybridization, and Polarity – Techiescientist
• SIS2 Lewis Structure: Drawings, Hybridization, Shape, Charges, Pair and Detailed Facts – Lambda Geeks
• Draw the Lewis structure for silicon disulfide, SiS2 – Chegg
• What is the Lewis dot structure for SiS2 – Brainly
• Which of these is the correct Lewis structure for SiS2? – Bartleby
• Draw the electron dot formula for silicon disulfide – Course Hero