OF3- 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.

OF3- lewis structure has an Oxygen atom (O) at the center which is surrounded by three Fluorine atoms (F). There are 3 single bonds between the Oxygen atom (O) and each Fluorine atom (F). There are 2 lone pairs on the Oxygen atom (O) and 3 lone pairs on all three Fluorine atoms (F). There is a -1 formal charge on the Oxygen atom (O).

If you haven’t understood anything from the above image of OF3- lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of OF3- ion.

So let’s move to the steps of drawing the lewis structure of OF3- ion.

Steps of drawing OF3- lewis structure

Step 1: Find the total valence electrons in OF3- ion

In order to find the total valence electrons in OF3- ion, first of all you should know the valence electrons present in the oxygen 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 oxygen as well as fluorine using a periodic table.

Total valence electrons in OF3- ion

→ Valence electrons given by oxygen atom:

Oxygen is group 16 element on the periodic table. ^[1] Hence the valence electrons present in oxygen is 6.

You can see the 6 valence electrons present in the oxygen 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 OF3- ion = valence electrons given by 1 oxygen 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 OF3- ion and it contains oxygen atom (O) and fluorine atoms (F).

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

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

So here the oxygen atom (O) 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 OF3 molecule, you have to put the electron pairs between the oxygen atom (O) and fluorine atoms (F).

This indicates that the oxygen (O) and fluorine (F) are chemically bonded with each other in a OF3 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 OF3 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 OF3- ion.

The OF3- 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 oxygen atom in the above sketch of OF3 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 OF3.

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 oxygen (O) atom as well as fluorine (F) atoms present in the OF3 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 OF3 molecule in the image given below.

For Oxygen (O) atom:
Valence electrons = 6 (because oxygen 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

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
O	=	6	–	6/2	–	4	=	-1
F	=	7	–	2/2	–	6	=	0

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

So let’s keep these charges on the respective atoms in the OF3 molecule.

This overall -1 charge on the OF3 molecule is represented in the image given below.

In the above lewis dot structure of OF3- ion, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of OF3- 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:

PH4+ Lewis Structure	SHF Lewis Structure
SeS3 Lewis Structure	IBr5 Lewis Structure
AsI3 Lewis Structure	SbF6- Lewis Structure