Lewis Structure of SF3- (With 5 Simple Steps to Draw!)

Lewis structure of SF3-

Ready to learn how to draw the lewis structure of SF3- ion?


Here, I have explained 5 simple steps to draw the lewis dot structure of SF3- ion (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 SF3- ion contains three single bonds between the Sulfur (S) atom and each Fluorine (F) atom. The Sulfur atom (S) is at the center and it is surrounded by 3 Fluorine atoms (F). The Sulfur atom has 2 lone pairs and all the three Fluorine atoms have 3 lone pairs. The Sulfur 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 SF3- ion).

5 Steps to Draw the Lewis Structure of SF3- ion

Step #1: Calculate the total number of valence electrons

Here, the given ion is SF3- ion. In order to draw the lewis structure of SF3- ion, first of all you have to find the total number of valence electrons present in the SF3- 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 SF3- ion

  • For Sulfur:

Sulfur is a group 16 element on the periodic table. [1]

Hence, the valence electrons present in sulfur is 6 (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 SF3- ion, 

Valence electrons given by Sulfur (S) atom = 6
Valence electrons given by each Fluorine (F) atom = 7
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in SF3- ion = 6 + 7(3) + 1 = 28

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 SF3- ion, if we compare the sulfur atom (S) and fluorine atom (F), then the sulfur is less electronegative than fluorine.

So, sulfur 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 SF3 molecule, put the two electrons (i.e electron pair) between each sulfur atom and fluorine atom to represent a chemical bond between them.

step 2

These pairs of electrons present between the Sulfur (S) and Fluorine (F) atoms form a chemical bond, which bonds the sulfur and fluorine atoms with each other in a SF3 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 SF3- ion, 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 SF3- ion are used in the above structure.

But there are total 28 valence electrons in SF3- ion (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 28 – 24 = 4.

So let’s keep these four electrons (i.e 2 electron pairs) on the central atom.

step 4

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 sulfur atom (S) 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 5
  • For Sulfur:
    Valence electron = 6 (as it is in group 16)
    Nonbonding electrons = 4
    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

Let’s keep these charges on the atoms in the above lewis structure.

step 6

As you can see in the above sketch, there is one -ve charge on the sulfur atom, which indicates the -1 formal charge on the SF3 molecule.

Hence, the above lewis structure of SF3- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of SF3- ion represents the single bond ( | ). So the above lewis dot structure of SF3- ion can also be represented as shown below.

SF3- Lewis structure

Related lewis structures for your practice:
Lewis Structure of CH3Br
Lewis Structure of CH3OCH3
Lewis Structure of HCOOH (Formic acid)
Lewis Structure of IF3
Lewis Structure of XeO4 

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