I’m super excited to teach you the lewis structure of SeS2 in just 6 simple steps.
Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of SeS2 molecule.
So, if you are ready to go with these 6 simple steps, then let’s dive right into it!
Lewis structure of SeS2 contains two double bonds between the Selenium (Se) atom and each Sulfur (S) atom. The Selenium atom (Se) is at the center and it is surrounded by 2 Sulfur atoms (S). The Selenium atom has 1 lone pair and both the Sulfur atoms have 2 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 SeS2).
6 Steps to Draw the Lewis Structure of SeS2
Step #1: Calculate the total number of valence electrons
Here, the given molecule is SeS2. In order to draw the lewis structure of SeS2, first of all you have to find the total number of valence electrons present in the SeS2 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 SeS2
- For Selenium:
Selenium is a group 16 element on the periodic table. 
Hence, the valence electrons present in selenium is 6 (see below image).
- For Sulfur:
Sulfur is a group 16 element on the periodic table. 
Hence, the valence electrons present in sulfur is 6 (see below image).
Hence in a SeS2 molecule,
Valence electrons given by Selenium (Se) atom = 6
Valence electrons given by each Sulfur (S) atom = 6
So, total number of Valence electrons in SeS2 molecule = 6 + 6(2) = 18
Step #2: Select the center atom
While selecting the 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). 
Here in the SeS2 molecule, if we compare the selenium atom (Se) and sulfur atom (S), then the selenium is less electronegative than sulfur.
So, selenium should be placed in the center and the remaining 2 sulfur atoms will surround it.
Step #3: Put two electrons between the atoms to represent a chemical bond
Now in the above sketch of SeS2 molecule, put the two electrons (i.e electron pair) between each selenium atom and sulfur atom to represent a chemical bond between them.
These pairs of electrons present between the Selenium (Se) and Sulfur (S) atoms form a chemical bond, which bonds the selenium and sulfur atoms with each other in a SeS2 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 SeS2, the outer atoms are sulfur atoms.
So now, you have to complete the octet on these sulfur atoms (because sulfur requires 8 electrons to have a complete outer shell).
Now, you can see in the above image that all the sulfur atoms form an octet.
Also, only 16 valence electrons of SeS2 molecule are used in the above structure.
But there are total 18 valence electrons in SeS2 molecule (as calculated in step #1).
So the number of electrons left to be kept on the central atom = 18 – 16 = 2.
So let’s keep these two electrons (i.e electron pair) on the central atom.
Now, 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 selenium) has an octet or not.
In simple words, we have to check whether the central Selenium (Se) atom has 8 electrons or not.
As you can see from the above image, the central atom (i.e selenium) has only 6 electrons. So it does not fulfill the octet rule.
Now, in order to fulfill the octet of selenium atom, we have to move the electron pair from the outer atom (i.e sulfur atom) to form a double bond.
Now you can see from the above image that the central atom (i.e selenium), is having 8 electrons. So it fulfills the octet rule.
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 selenium atom (Se) as well as each sulfur atom (S).
For that, you need to remember the formula of formal charge;
Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2
- For Selenium:
Valence electrons = 6 (as it is in group 16)
Nonbonding electrons = 2
Bonding electrons = 6
- For 1st Sulfur:
Valence electron = 6 (as it is in group 16)
Nonbonding electrons = 4
Bonding electrons = 4
- For 2nd Sulfur:
Valence electron = 6 (as it is in group 16)
Nonbonding electrons = 6
Bonding electrons = 2
|Formal charge||=||Valence electrons||–||Nonbonding electrons||–||(Bonding electrons)/2|
So you can see above that the formal charges on selenium is +1 and the formal charge on the 2nd sulfur atom is -1.
This indicates that the above lewis structure of SeS2 is not stable and so we have to minimize the charges to get a more stable lewis structure.
This can be done by shifting the lone pair from negatively charged sulfur atom to the positively charged selenium atom to form a bond.
Now, in the above structure, you can see that the charges are minimized and the above lewis structure of SeS2 is the final stable structure.
Each electron pair (:) in the lewis dot structure of SeS2 represents the single bond ( | ). So the above lewis dot structure of SeS2 can also be represented as shown below.
Related lewis structures for your practice:
Lewis Structure of TeBr4
Lewis Structure of NO4 3-
Lewis Structure of C2H2F2
Lewis Structure of C2Br2
Lewis Structure of GeCl4