Lewis Structure of AsF3 (With 6 Simple Steps to Draw!)

Lewis Structure of AsF3

Ready to learn how to draw the lewis structure of AsF3?


Here, I have explained 6 simple steps to draw the lewis dot structure of AsF3 (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 AsF3 contains three single bonds between the Arsenic (As) atom and each Fluorine (F) atom. The Arsenic atom (As) is at the center and it is surrounded by 3 Fluorine atoms (F). The Arsenic atom has 1 lone pair and all the three Fluorine atoms have 3 lone pairs.

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 AsF3).

6 Steps to Draw the Lewis Structure of AsF3

Step #1: Calculate the total number of valence electrons

Here, the given molecule is AsF3. In order to draw the lewis structure of AsF3, first of all you have to find the total number of valence electrons present in the AsF3 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 AsF3

  • For Arsenic:

Arsenic is a group 15 element on the periodic table. [1]

Hence, the valence electrons present in arsenic is 5 (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 AsF3 molecule, 

Valence electrons given by Arsenic (As) atom = 5
Valence electrons given by each Fluorine (F) atom = 7
So, total number of Valence electrons in AsF3 molecule = 5 + 7(3) = 26

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). [3]

Here in the AsF3 molecule, if we compare the arsenic atom (As) and fluorine atom (F), then the arsenic is less electronegative than fluorine.

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

step 1

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

Now in the above sketch of AsF3 molecule, put the two electrons (i.e electron pair) between each arsenic atom and fluorine atom to represent a chemical bond between them.

step 2

These pairs of electrons present between the Arsenic (As) and Fluorine (F) atoms form a chemical bond, which bonds the arsenic and fluorine atoms with each other in a AsF3 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 AsF3, 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).

step 3

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

Also, only 24 valence electrons of AsF3 molecule are used in the above structure.

But there are total 26 valence electrons in AsF3 molecule (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 26 – 24 = 2.

So let’s keep these two electrons (i.e electron pair) on the central atom.

step 4

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 arsenic) has an octet or not. 

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

step 5

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

step 6
  • For Arsenic:
    Valence electron = 5 (as it is in group 15)
    Nonbonding electrons = 2
    Bonding electrons = 6
  • For Fluorine:
    Valence electron = 7 (as it is in group 17)
    Nonbonding electrons = 6
    Bonding electrons = 2
Formal charge=Valence electronsNonbonding electrons(Bonding electrons)/2

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

Hence, there will not be any change in the above structure and the above lewis structure of AsF3 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of AsF3 represents the single bond ( | ). So the above lewis dot structure of AsF3 can also be represented as shown below.

AsF3 lewis structure

Related lewis structures for your practice:
Lewis Structure of KrF2
Lewis Structure of SO2Cl2
Lewis Structure of C4H10 (Butane)
Lewis Structure of C2H3Cl
Lewis Structure of CH2Br2 

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Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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