AsCl3 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.

AsCl3 lewis structure has an Arsenic atom (As) at the center which is surrounded by three Chlorine atoms (Cl). There are 3 single bonds between the Arsenic atom (As) and each Chlorine atom (Cl). There is 1 lone pair on the Arsenic atom (As) and 3 lone pairs on all three Chlorine atoms (Cl).

If you haven’t understood anything from the above image of AsCl3 lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of AsCl3.

So let’s move to the steps of drawing the lewis structure of AsCl3.

Steps of drawing AsCl3 lewis structure

Step 1: Find the total valence electrons in AsCl3 molecule

In order to find the total valence electrons in AsCl3 molecule, first of all you should know the valence electrons present in arsenic 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 arsenic as well as chlorine using a periodic table.

Total valence electrons in AsCl3 molecule

→ Valence electrons given by arsenic atom:

Arsenic is a group 15 element on the periodic table. ^[1] Hence the valence electrons present in arsenic is 5.

You can see the 5 valence electrons present in the arsenic 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 AsCl3 molecule = valence electrons given by 1 arsenic atom + valence electrons given by 3 chlorine atoms = 5 + 7(3) = 26.

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 AsCl3 and it contains arsenic atom (As) and chlorine atoms (Cl).

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

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

So here the arsenic atom (As) 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 AsCl3 molecule, you have to put the electron pairs between the arsenic atom (As) and chlorine atoms (Cl).

This indicates that the arsenic (As) and chlorine (Cl) are chemically bonded with each other in a AsCl3 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 AsCl3 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 AsCl3 molecule.

The AsCl3 molecule has a total 26 valence electrons and out of these, only 24 valence electrons are used in the above sketch.

So the number of electrons which are left = 26 – 24 = 2.

You have to put these 2 electrons on the central arsenic atom in the above sketch of AsCl3 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 arsenic atom (As) is stable or not.

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

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

And hence the central arsenic atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of AsCl3 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 AsCl3.

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 arsenic (As) atom as well as chlorine (Cl) atoms present in the AsCl3 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 AsCl3 molecule in the image given below.

For Arsenic (As) atom:
Valence electrons = 5 (because arsenic is in group 15)
Bonding electrons = 6
Nonbonding electrons = 2

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

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
As	=	5	–	6/2	–	2	=	0
Cl	=	7	–	2/2	–	6	=	0

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

This indicates that the above lewis structure of AsCl3 is stable and there is no further change in the above structure of AsCl3.

In the above lewis dot structure of AsCl3, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of AsCl3.

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:

C2H2Br2 Lewis Structure	SbCl5 Lewis Structure
CH3SH Lewis Structure	KrF4 Lewis Structure
TeCl4 Lewis Structure	AsO4 3- Lewis Structure