Lewis Structure of BCl3 (With 5 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of BCl3?

Awesome!

Here, I have explained 5 simple steps to draw the lewis dot structure of BCl3 (along with images).

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

Lewis structure of BCl3 contains three single bonds between the Boron (B) atom and each Chlorine (Cl) atom. The Boron atom (B) is at the center and it is surrounded by 3 Chlorine atoms (Cl). The Boron atom does not have a lone pair while all three chlorine atoms have three lone pairs each.

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 BCl3).

5 Steps to Draw the Lewis Structure of BCl3

Step #1: Calculate the total number of valence electrons

Here, the given molecule is BCl3. In order to draw the lewis structure of BCl3, first of all you have to find the total number of valence electrons present in the BCl3 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 BCl3

• For Boron:

Boron is a group 13 element on the periodic table. ^[1]

Hence, the valence electrons present in boron is 3 (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 BCl3 molecule, 

Valence electrons given by Boron (B) atom = 3
Valence electrons given by each Chlorine (Cl) atom = 7
So, total number of Valence electrons in BCl3 molecule = 3 + 7(3) = 24

Step #2: Select the center atom

While selecting the center 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 BCl3 molecule, if we compare the boron atom (B) and chlorine atom (Cl), then boron is less electronegative than chlorine.

So, boron should be placed in the center and the remaining 3 chlorine atoms will surround it.

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

Now in the above sketch of BCl3 molecule, put the two electrons (i.e electron pair) between each boron atom and chlorine atom to represent a chemical bond between them.

These pairs of electrons present between the Boron (B) and Chlorine (Cl) atoms form a chemical bond, which bonds the boron and chlorine atoms with each other in a BCl3 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 BCl3, 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, all the 24 valence electrons of BCl3 molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of BCl3.

Let’s move to the next step.

Step #5: 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 boron atom (B) 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 Boron:
  Valence electrons = 3 (as it is in group 13)
  Nonbonding electrons = 0
  Bonding electrons = 6
• 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
B	=	3	–	0	–	6/2	=	0
Cl	=	7	–	6	–	2/2	=	0

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

Hence, there will not be any change in the above structure and the above lewis structure of BCl3 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of BCl3 represents the single bond ( | ). So the above lewis dot structure of BCl3 can also be represented as shown below.

Related lewis structures for your practice:
Lewis structure of CF4
Lewis structure of XeF2
Lewis structure of XeF4
Lewis structure of PO43-
Lewis structure of I3-

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