Lewis Structure of BF3 (With 5 Simple Steps to Draw!)

I’m super excited to teach you the lewis structure of BF3 in just 5 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of BF3 molecule.

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

Lewis structure of BF3 contains three single bonds between the Boron (B) atom and each Fluorine (F) atom. The Boron atom (B) is at the center and it is surrounded by 3 Fluorine atoms (F). The Boron atom does not have a lone pair while all three fluorine 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 BF3).

5 Steps to Draw the Lewis Structure of BF3

Step #1: Calculate the total number of valence electrons

Here, the given molecule is BF3. In order to draw the lewis structure of BF3, first of all you have to find the total number of valence electrons present in the BF3 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 BF3

• 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 Fluorine:

Fluorine is a group 17 element on the periodic table. ^[2]

Hence, the valence electrons present in fluorine is 7 (see below image).

Hence in a BF3 molecule, 

Valence electrons given by Boron (B) atom = 3
Valence electrons given by each Fluorine (F) atom = 7
So, total number of Valence electrons in BF3 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 BF3 molecule, if we compare the boron atom (B) and fluorine atom (F), then boron is less electronegative than fluorine.

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

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

Now in the above sketch of BF3 molecule, put the two electrons (i.e electron pair) between each boron atom and fluorine atom to represent a chemical bond between them.

These pairs of electrons present between the Boron (B) and Fluorine (F) atoms form a chemical bond, which bonds the boron and fluorine atoms with each other in a BF3 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 BF3, the outer atoms are fluorine atoms.

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

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

Also, all the 24 valence electrons of BF3 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 BF3.

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 fluorine atom (F).

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 Fluorine:
  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
F	=	7	–	6	–	2/2	=	0

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

Hence, there will not be any change in the above structure and the above lewis structure of BF3 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of BF3 represents the single bond ( | ). So the above lewis dot structure of BF3 can also be represented as shown below.

Related lewis structures for your practice:
Lewis structure of NO3 –
Lewis structure of O3
Lewis structure of C2H2
Lewis structure of CH2O
Lewis structure of SO3

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