Lewis Structure of PCl2- (With 6 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of PCl2- ion?

Awesome!

Here, I have explained 6 simple steps to draw the lewis dot structure of PCl2- ion (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 PCl2– ion contains a single bond between the Phosphorus (P) atom and Chlorine (Cl) atoms. The Phosphorus atom (P) is at the center and it is surrounded by 2 Chlorine atoms (Cl). The Phosphorus atom has 2 lone pairs, and both the Chlorine atom has 3 lone pairs. The Phosphorus 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 PCl2- ion).

6 Steps to Draw the Lewis Structure of PCl2- ion

Step #1: Calculate the total number of valence electrons

Here, the given ion is PCl2- ion. In order to draw the lewis structure of PCl2- ion, first of all you have to find the total number of valence electrons present in the PCl2- 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 PCl2- ion

• For Phosphorus: 

Phosphorus is a group 15 element on the periodic table.

Hence, the valence electrons present in phosphorus is 5 (see below image).

• For Chlorine:

Chlorine is a group 17 element on the periodic table.

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

Hence in a PCl2- ion, 

Valence electrons given by Phosphorus (P) atom = 5
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 PCl2- ion = 5 + 7(2) + 1 = 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). ^[1]

Here in the PCl2 molecule, if we compare the phosphorus atom (P) and chlorine atom (Cl), then the phosphorus is less electronegative than chlorine.

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

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

Now in the above sketch of a PCl2 molecule, put the two electrons (i.e electron pair) between each phosphorus atom and chlorine atom to represent a chemical bond between them.

These pairs of electrons present between the Phosphorus (P) and Chlorine (Cl) atoms form a chemical bond, which bonds the phosphorus and chlorine atoms with each other in a PCl2 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 PCl2, 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).

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

Also, only 16 valence electrons of PCl2 molecule are used in the above structure.

But there are total 20 valence electrons in PCl2 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.

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 phosphorus) has an octet or not. 

In simple words, we have to check whether the central Phosphorus (P) atom is having 8 electrons or not.

As you can see from the above image, the central atom (i.e phosphorus), has 8 electrons. So it fulfills the octet rule and the phosphorus 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 phosphorus atom (P) 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

• For Phosphorus:
  Valence electron = 5 (as it is in group 15)
  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 electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
P	=	5	–	4	–	4/2	=	-1
Cl	=	7	–	6	–	2/2	=	0

Let’s keep these charges on the atoms in the above lewis structure of PCl2- ion.

As you can see in the above sketch, there is one -ve charge on the phosphorus atom, which indicates the -1 formal charge on the PCl2 molecule.

Hence, the above lewis structure of PCl2- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of PCl2- ion represents the single bond ( | ). So the above lewis dot structure of PCl2- ion can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of AsO2-
Lewis Structure of SBr4
Lewis Structure of BrCl5
Lewis Structure of CFCl3
Lewis Structure of NCl2- 

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