OF3- Lewis structure

OF₃^– has one oxygen atom and three fluorine atoms.

In OF₃^– Lewis structure, there are three single bonds around the oxygen atom, with three fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the oxygen atom has two lone pairs.

Also, there is a negative (-1) charge on the oxygen atom.

Alternative method: Lewis structure of OF₃^–

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, oxygen lies in group 16, and fluorine lies in group 17.

Hence, oxygen has six valence electrons and fluorine has seven valence electrons.

Since OF₃^– has one oxygen atom and three fluorine atoms, so…

Valence electrons of one oxygen atom = 6 × 1 = 6
Valence electrons of three fluorine atoms = 7 × 3 = 21

Now the OF₃^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 6 + 21 + 1 = 28

Learn how to find: Oxygen valence electrons and Fluorine valence electrons

• Second, find the total electron pairs

We have a total of 28 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 28 ÷ 2 = 14

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since oxygen is less electronegative than fluorine, assume that the central atom is oxygen.

Therefore, place oxygen in the center and fluorines on either side.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 14 electron pairs. And three O — F bonds are already marked. So we have to only mark the remaining eleven electron pairs as lone pairs on the sketch.

Also remember that both (oxygen and fluorine) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are fluorines.

So for each fluorine, there are three lone pairs, and for oxygen, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

Formal charge

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For oxygen atom, formal charge = 6 – 4 – ½ (6) = -1

For each fluorine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, the oxygen atom has a charge, so mark it on the sketch as follows:

Final structure

The final structure of OF₃^– comprises a central oxygen atom linked to three fluorine atoms through single covalent bonds. In this configuration, the oxygen atom utilizes an expanded valence shell to accommodate ten electrons, forming three bonding pairs and retaining two lone pairs. Within this layout, each of the three fluorine atoms successfully reaches a stable octet by maintaining three lone pairs alongside its single shared bond. This arrangement represents the most stable state for the ion because it minimizes the magnitude of formal charges across the structure, with the negative formal charge residing on the central oxygen atom. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of OF₃^–.

To properly represent this as a polyatomic ion, the entire Lewis structure is enclosed within square brackets. The overall charge of 1- is then written as a superscript outside the brackets at the top right, indicating that the structure possesses one additional electron beyond the valence count of the neutral atoms.

Next: PH₄⁺ Lewis structure