SeCl2 Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

SeCl2 lewis structure has a Selenium atom (Se) at the center which is surrounded by two Chlorine atoms (Cl). There are 2 single bonds between the Selenium atom (Se) and each Chlorine atom (Cl). There are 2 lone pairs on the Selenium atom (Se) and 3 lone pairs on both the Chlorine atoms (Cl).

If you haven’t understood anything from the above image of SeCl2 lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of SeCl2.

So let’s move to the steps of drawing the lewis structure of SeCl2.

Steps of drawing SeCl2 lewis structure

Step 1: Find the total valence electrons in SeCl2 molecule

In order to find the total valence electrons in a SeCl2 molecule, first of all you should know the valence electrons present in selenium atom as well as chlorine 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 selenium as well as chlorine using a periodic table.

Total valence electrons in SeCl2 molecule

→ Valence electrons given by selenium atom:

Selenium is a group 16 element on the periodic table. ^[1] Hence the valence electrons present in selenium is 6.

You can see the 6 valence electrons present in the selenium atom as shown in the above image.

→ Valence electrons given by chlorine atom:

Chlorine is group 17 element on the periodic table. ^[2] Hence the valence electrons present in chlorine is 7.

You can see the 7 valence electrons present in the chlorine atom as shown in the above image.

Hence, 

Total valence electrons in SeCl2 molecule = valence electrons given by 1 selenium atom + valence electrons given by 2 chlorine atoms = 6 + 7(2) = 20.

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 SeCl2 and it contains selenium atom (Se) and chlorine atoms (Cl).

You can see the electronegativity values of selenium atom (Se) and chlorine atom (Cl) in the above periodic table.

If we compare the electronegativity values of selenium (Se) and chlorine (Cl) then the selenium atom is less electronegative.

So here the selenium atom (Se) is the center atom and the chlorine atoms (Cl) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the SeCl2 molecule, you have to put the electron pairs between the selenium atom (Se) and chlorine atoms (Cl).

This indicates that the selenium (Se) and chlorine (Cl) are chemically bonded with each other in a SeCl2 molecule.

Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of SeCl2 molecule, you can see that the outer atoms are chlorine atoms.

These outer chlorine 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 SeCl2 molecule.

The SeCl2 molecule has a total 20 valence electrons and out of these, only 16 valence electrons are used in the above sketch.

So the number of electrons which are left = 20 – 16 = 4.

You have to put these 4 electrons on the central selenium atom in the above sketch of SeCl2 molecule.

Now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central selenium atom (Se) is stable or not.

In order to check the stability of the central selenium (Se) atom, we have to check whether it is forming an octet or not.

You can see from the above picture that the selenium atom is forming an octet. That means it has 8 electrons.

And hence the central selenium atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of SeCl2 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 SeCl2.

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 selenium (Se) atom as well as chlorine (Cl) atoms present in the SeCl2 molecule.

For calculating the formal charge, you have to use the following formula;

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

You can see the number of bonding electrons and nonbonding electrons for each atom of SeCl2 molecule in the image given below.

For Selenium (Se) atom:
Valence electrons = 6 (because selenium is in group 16)
Bonding electrons = 4
Nonbonding electrons = 4

For Chlorine (Cl) atom:
Valence electron = 7 (because chlorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
Se	=	6	–	4/2	–	4	=	0
Cl	=	7	–	2/2	–	6	=	0

From the above calculations of formal charge, you can see that the selenium (Se) atom as well as chlorine (Cl) atom has a “zero” formal charge.

This indicates that the above lewis structure of SeCl2 is stable and there is no further change in the above structure of SeCl2.

In the above lewis dot structure of SeCl2, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of SeCl2.

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:

IBr3 Lewis Structure	HBrO Lewis Structure
IO2- Lewis Structure	CI4 Lewis Structure
BI3 Lewis Structure	CH3I Lewis Structure