SiS2 Lewis structure

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SiS₂ (silicon disulfide) has one silicon atom and two sulfur atoms.

In the SiS₂ Lewis structure, there are two double bonds around the silicon atom, with two sulfur atoms attached to it, and on each sulfur atom, there are two lone pairs.

Steps

Here’s how you can easily draw the SiS₂ Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms
#4 Minimize formal charges by converting lone pairs of the atoms, and try to get a stable Lewis structure
#5 Repeat step 4 again if needed, until all charges are minimized

Now, let’s take a closer look at each step mentioned above.

#1 Draw a rough skeleton structure

• First, determine the total number of valence electrons

In the periodic table, silicon lies in group 14, and sulfur lies in group 16.

Hence, silicon has four valence electrons and sulfur has six valence electrons.

Since SiS₂ has one silicon atom and two sulfur atoms, so…

Valence electrons of one silicon atom = 4 × 1 = 4
Valence electrons of two sulfur atoms = 6 × 2 = 12

And the total valence electrons = 4 + 12 = 16

Learn how to find: Silicon valence electrons and Sulfur valence electrons

• Second, find the total electron pairs

We have a total of 16 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 = 16 ÷ 2 = 8

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

#2 Mention lone pairs on the atoms

Here, we have a total of 8 electron pairs. And two Si — S bonds are already marked. So we have to only mark the remaining six electron pairs as lone pairs on the sketch.

Also remember that both (silicon and sulfur) 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 sulfurs.

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

Mark the lone pairs on the sketch as follows:

#3 If needed, mention formal charges on the atoms

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 (4) = +2

For each sulfur atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both silicon and sulfur atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both silicon and sulfur atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

#4 Minimize formal charges by converting lone pairs of the atoms

Convert a lone pair of the sulfur atom to make a new Si — S bond with the silicon atom as follows:

#5 Since there are charges on atoms, repeat step 4 again

Since there are charges on silicon and sulfur atoms, again convert a lone pair of the sulfur atom to make a new Si — S bond with the silicon atom as follows:

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

Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable Lewis structure of SiS₂.

Next: COF₂ Lewis structure

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External links

• https://geometryofmolecules.com/sis2-lewis-structure-hybridization-molecular-geometry-bond-angles/
• https://techiescientist.com/sis2-lewis-structure/
• https://lambdageeks.com/sis2-lewis-structure/
• https://oneclass.com/homework-help/chemistry/7030403-sis2-lewis-structure.en.html