So you have seen the above image by now, right?
Let me explain the above image in short.
SiS2 lewis structure has a Silicon atom (Si) at the center which is surrounded by two Sulfur atoms (S). There are 2 double bonds between the Silicon atom (Si) and each Sulfur atom (S). There are 2 lone pairs on both the Sulfur atoms (S).
If you haven’t understood anything from the above image of SiS2 (silicon disulfide) lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of SiS2.
So let’s move to the steps of drawing the lewis structure of SiS2.
Steps of drawing SiS2 lewis structure
Step 1: Find the total valence electrons in SiS2 molecule
In order to find the total valence electrons in a SiS2 (silicon disulfide) molecule, first of all you should know the valence electrons present in silicon atom as well as sulfur atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)
Here, I’ll tell you how you can easily find the valence electrons of silicon as well as sulfur using a periodic table.
Total valence electrons in SiS2 molecule
→ Valence electrons given by silicon atom:
Silicon is a group 14 element on the periodic table.  Hence the valence electrons present in silicon is 4.
You can see the 4 valence electrons present in the silicon atom as shown in the above image.
→ Valence electrons given by sulfur atom:
Sulfur is a group 16 element on the periodic table.  Hence the valence electrons present in sulfur is 6.
You can see the 6 valence electrons present in the sulfur atom as shown in the above image.
Total valence electrons in SiS2 molecule = valence electrons given by 1 silicon atom + valence electrons given by 2 sulfur atoms = 4 + 6(2) = 16.
Step 2: Select the central atom
For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.
Now here the given molecule is SiS2 (silicon disulfide) and it contains silicon atom (Si) and sulfur atoms (S).
You can see the electronegativity values of silicon atom (Si) and sulfur atom (S) in the above periodic table.
If we compare the electronegativity values of silicon (Si) and sulfur (S) then the silicon atom is less electronegative.
So here the silicon atom (Si) is the center atom and the sulfur atoms (S) are the outside atoms.
Step 3: Connect each atoms by putting an electron pair between them
Now in the SiS2 molecule, you have to put the electron pairs between the silicon atom (Si) and sulfur atoms (S).
This indicates that the silicon (Si) and sulfur (S) are chemically bonded with each other in a SiS2 molecule.
Step 4: Make the outer atoms stable
Now in this step, you have to check the stability of the outer atoms.
Here in the sketch of SiS2 molecule, you can see that the outer atoms are sulfur atoms.
These outer sulfur atoms are forming an octet and hence they are stable.
Also, in step 1 we have calculated the total number of valence electrons present in the SiS2 molecule.
The SiS2 molecule has a total 16 valence electrons and all these valence electrons are used in the above sketch of SiS2.
Hence there are no remaining electron pairs to be kept on the central atom.
So now let’s proceed to the next step.
Step 5: Check the octet on the central atom. If it does not have octet, then shift the lone pair to form a double bond or triple bond.
In this step, you have to check whether the central silicon atom (Si) is stable or not.
In order to check the stability of the central silicon (Si) atom, we have to check whether it is forming an octet or not.
Unfortunately, the silicon atom is not forming an octet here. Silicon has only 4 electrons and it is unstable.
Now to make this silicon atom stable, you have to shift the electron pair from the outer sulfur atom so that the silicon atom can have 8 electrons (i.e octet).
But after shifting one electron pair, the silicon atom is still not forming an octet as it has only 6 electrons.
So again we have to shift one more electron pair from the other sulfur atom.
After shifting this electron pair, the central silicon atom will get 2 more electrons and thus its total electrons will become 8.
You can see from the above picture that the silicon atom is forming an octet.
And hence the silicon atom is stable.
Now let’s proceed to the final step to check whether the lewis structure of SiS2 is stable or not.
Step 6: Check the stability of lewis structure
Now you have come to the final step in which you have to check the stability of lewis structure of SiS2.
The stability of lewis structure can be checked by using a concept of formal charge.
In short, now you have to find the formal charge on silicon (Si) atom as well as sulfur (S) atoms present in the SiS2 molecule.
For calculating the formal charge, you have to use the following formula;
Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons
For Silicon (Si) atom:
Valence electrons = 4 (because silicon is in group 14)
Bonding electrons = 8
Nonbonding electrons = 0
For Sulfur (S) atom:
Valence electrons = 6 (because sulfur is in group 16)
Bonding electrons = 4
Nonbonding electrons = 4
From the above calculations of formal charge, you can see that the silicon (Si) atom as well as sulfur (S) atom has a “zero” formal charge.
This indicates that the above lewis structure of SiS2 is stable and there is no further change in the above structure of SiS2.
In the above lewis dot structure of SiS2, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of SiS2.
I hope you have completely understood all the above steps.
For more practice and better understanding, you can try other lewis structures listed below.
Try (or at least See) these lewis structures for better understanding:
|OCS Lewis Structure
|Br3- Lewis Structure
|H3O+ Lewis Structure
|CH3NO2 Lewis Structure
|AsH3 Lewis Structure
|SeF6 Lewis Structure
Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.
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