SF3- Lewis Structure in 5 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

SF3- lewis structure has a Sulfur atom (S) at the center which is surrounded by three Fluorine atoms (F). There are 3 single bonds between the Sulfur atom (S) and each Fluorine atom (F). There are 2 lone pairs on the Sulfur atom (S) and 3 lone pairs on all three Fluorine atoms (F). There is a -1 formal charge on the Sulfur atom (S).

If you haven’t understood anything from the above image of SF3- lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of SF3- ion.

So let’s move to the steps of drawing the lewis structure of SF3- ion.

Steps of drawing SF3- lewis structure

Step 1: Find the total valence electrons in SF3- ion

In order to find the total valence electrons in SF3- ion, first of all you should know the valence electrons present in the sulfur atom as well as fluorine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of sulfur as well as fluorine using a periodic table.

Total valence electrons in SF3- ion

→ Valence electrons given by sulfur atom:

Sulfur is a group 16 element on the periodic table. ^[1] Hence the valence electrons present in sulfur is 6.

You can see the 6 valence electrons present in the sulfur atom as shown in the above image.

→ Valence electrons given by fluorine atom:

Fluorine is group 17 element on the periodic table. ^[2] Hence the valence electron present in fluorine is 7.

You can see the 7 valence electrons present in the fluorine atom as shown in the above image.

Hence, 

Total valence electrons in SF3- ion = valence electrons given by 1 sulfur atom + valence electrons given by 3 fluorine atoms + 1 more electron is added due to 1 negative charge = 6 + 7(3) + 1 = 28.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

Now here the given ion is SF3- ion and it contains sulfur atom (S) and fluorine atoms (F).

You can see the electronegativity values of sulfur atom (S) and fluorine atom (F) in the above periodic table.

If we compare the electronegativity values of sulfur (S) and fluorine (F) then the sulfur atom is less electronegative.

So here the sulfur atom (S) is the center atom and the fluorine atoms (F) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the SF3 molecule, you have to put the electron pairs between the sulfur atom (S) and fluorine atoms (F).

This indicates that the sulfur (S) and fluorine (F) are chemically bonded with each other in a SF3 molecule.

Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of SF3 molecule, you can see that the outer atoms are fluorine atoms.

These outer fluorine atoms are forming an octet and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the SF3- ion.

The SF3- ion has a total 28 valence electrons and out of these, only 24 valence electrons are used in the above sketch.

So the number of electrons which are left = 28 – 24 = 4.

You have to put these 4 electrons on the central sulfur atom in the above sketch of SF3 molecule.

Now let’s proceed to the next step.

Step 5: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of SF3.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on sulfur (S) atom as well as fluorine (F) atoms present in the SF3 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of SF3 molecule in the image given below.

For Sulfur (S) atom:
Valence electrons = 6 (because sulfur is in group 16)
Bonding electrons = 6
Nonbonding electrons = 4

For Fluorine (F) atom:
Valence electrons = 7 (because fluorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6

From the above calculations of formal charge, you can see that the sulfur (S) atom has -1 charge and the fluorine (F) atom has 0 charge.

So let’s keep these charges on the respective atoms in the SF3 molecule.

This overall -1 charge on the SF3 molecule is represented in the image given below.

In the above lewis dot structure of SF3- ion, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of SF3- ion.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

About author

Jay Rana

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. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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