Lewis Structure of SeCl2 (With 6 Simple Steps to Draw!)

Lewis Structure of SeCl2

Ready to learn how to draw the lewis structure of SeCl2?


Here, I have explained 6 simple steps to draw the lewis dot structure of SeCl2 (along with images).

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

Lewis structure of SeCl2 contains two single bonds between the Selenium (Se) atom and each Chlorine (Cl) atom. The Selenium atom (Se) is at the center and it is surrounded by 2 Chlorine atoms (Cl). The Selenium atom has 2 lone pairs and 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 SeCl2).

6 Steps to Draw the Lewis Structure of SeCl2

Step #1: Calculate the total number of valence electrons

Here, the given molecule is SeCl2. In order to draw the lewis structure of SeCl2, first of all you have to find the total number of valence electrons present in the SeCl2 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 SeCl2

  • For Selenium: 

Selenium is a group 16 element on the periodic table. [1]

Hence, the valence electrons present in selenium is 6 (see below image).

  • For Chlorine:

Chlorine is a group 17 element on the periodic table. [2]

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

Hence in a SeCl2 molecule, 

Valence electrons given by Selenium (Se) atom = 6
Valence electrons given by each Chlorine (Cl) atom = 7
So, total number of Valence electrons in SeCl2 molecule = 6 + 7(2) = 20

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). [3]

Here in the SeCl2 molecule, if we compare the selenium atom (Se) and chlorine atom (Cl), then the selenium is less electronegative than chlorine.

So, selenium should be placed in the center and the remaining 2 chlorine atoms will surround it.

step 1

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

Now in the above sketch of SeCl2 molecule, put the two electrons (i.e electron pair) between each selenium atom and chlorine atom to represent a chemical bond between them.

step 2

These pairs of electrons present between the Selenium (Se) and Chlorine (Cl) atoms form a chemical bond, which bonds the selenium and chlorine atoms with each other in a SeCl2 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 SeCl2, the outer atoms are chlorine atoms.

So now, you have to complete the octet on these chlorine atoms (because chlorine requires 8 electrons to have a complete outer shell).

step 3

Now, you can see in the above image that all the chlorine atoms form an octet.

Also, only 16 valence electrons of SeCl2 molecule are used in the above structure.

But there are total 20 valence electrons in SeCl2 molecule (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 20 – 16 = 4.

So let’s keep these four electrons (i.e 2 electron pairs) on the central atom.

step 4

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 is having 8 electrons or not.

step 5

As you can see from the above image, the central atom (i.e selenium), has 8 electrons. So it fulfills the octet rule and the selenium 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 selenium atom (Se) as well as each chlorine atom (Cl).

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

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

step 6
  • For Selenium:
    Valence electron = 6 (as it is in group 16)
    Nonbonding electrons = 4
    Bonding electrons = 4
  • For Chlorine:
    Valence electron = 7 (as it is in group 17)
    Nonbonding electrons = 6
    Bonding electrons = 2
Formal charge=Valence electronsNonbonding electrons(Bonding electrons)/2

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

Hence, there will not be any change in the above structure and the above lewis structure of SeCl2 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of SeCl2 represents the single bond ( | ). So the above lewis dot structure of SeCl2 can also be represented as shown below.

secl2 lewis structure

Related lewis structures for your practice:
Lewis Structure of C2F4
Lewis Structure of IBr3
Lewis Structure of HBrO
Lewis Structure of IO2-
Lewis Structure of CI4 

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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. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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