Lewis Structure of Cl3- (With 5 Simple Steps to Draw!)

I’m super excited to teach you the lewis structure of Cl3- ion in just 5 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of Cl3- ion.

So, if you are ready to go with these 5 simple steps, then let’s dive right into it!

Lewis structure of Cl3- ion contains two single bonds between each Chlorine (Cl) atom. All the three Chlorine atoms have three lone pairs on it, and the central chlorine atom has -1 formal charge.

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 Cl3- ion).

6 Steps to Draw the Lewis Structure of Cl3-

Step #1: Calculate the total number of valence electrons

Here, the given ion is Cl3^–. In order to draw the lewis structure of Cl3^– ion, first of all you have to find the total number of valence electrons present in the Cl3^– ion.
(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 Cl3^– ion

• For Chlorine:

Chlorine is a group 17 element on the periodic table. ^[1]

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

Hence in a Cl3^– ion, 

Valence electrons given by each Chlorine (Cl) atom = 7
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in Cl3^– ion = 7(3) + 1 = 22

Step #2: Select the center atom

While selecting the atom, you have to put the least electronegative atom at the center. 

But here in the Cl3- ion, all three atoms are same. So you can simply put any chlorine atom at center and place other chlorine atoms surrounding it.

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

Now in the above sketch of Cl3 molecule, put the two electrons (i.e electron pair) between all the three chlorine atoms to represent a chemical bond between them.

These pair of electrons present between the Chlorine (Cl) atoms form a chemical bond, which bonds all the chlorine atoms with each other in a Cl3- ion.

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 Cl3^– ion, the outer atoms are chlorine atoms only.

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

Also, only 16 valence electrons of Cl3- ion are used in the above structure.

But there are total 22 valence electrons in Cl3- ion (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 22 – 16 = 6.

So let’s keep these six electrons (i.e three electron pairs) on the central chlorine atom.

Now, let’s move to the next step.

Step #5: Check the formal charge

Now, you have come to the final step and here you have to check the formal charge on Cl3- ion. 

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

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

• For central Chlorine:
  Valence electrons = 7 (as it is in group 17)
  Nonbonding electrons = 6
  Bonding electrons = 4
• For outer Chlorine:
  Valence electron = 7 (as it is in group 17)
  Nonbonding electrons = 6
  Bonding electrons = 2

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
Central Cl	=	7	–	6	–	4/2	=	-1
Outer Cl	=	7	–	6	–	2/2	=	0

Let’s keep these charges on the atoms in the above lewis structure of Cl3^– ion.

As you can see in the above sketch, there is one -ve charge on the central chlorine atom, which indicates the -1 formal charge on the Cl3 molecule.

Hence, the above lewis structure of Cl3- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of Cl3- ion represents the single bond ( | ). So the above lewis dot structure of Cl3- ion can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of PCl2-
Lewis Structure of AsO2-
Lewis Structure of SBr4
Lewis Structure of BrCl5
Lewis Structure of CFCl3 

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