CF3- Lewis structure

CF₃^– has one carbon atom and three fluorine atoms.

In CF₃^– Lewis structure, there are three single bonds around the carbon atom, with three fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the carbon atom has one lone pair.

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

Alternative method: Lewis structure of CF₃^–

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, carbon lies in group 14, and fluorine lies in group 17.

Hence, carbon has four valence electrons and fluorine has seven valence electrons.

Since CF₃^– has one carbon atom and three fluorine atoms, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of three fluorine atoms = 7 × 3 = 21

Now the CF₃^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 4 + 21 + 1 = 26

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

• Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 13 electron pairs. And three C — F bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

Also remember that both (carbon 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 carbon, there is one lone pair.

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 carbon atom, formal charge = 4 – 2 – ½ (6) = -1

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

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

Final structure

The final structure of CF₃^– includes a central carbon atom linked to three fluorine atoms through single covalent bonds. In this arrangement, the carbon atom satisfies the octet rule by forming three bonding pairs and retaining one lone pair. 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 configuration represents the most stable state for the ion because the negative formal charge is localized on the central carbon atom, while each fluorine atom maintains a formal charge of zero. Thus, this specific electronic distribution serves as the definitive and most accurate Lewis representation of CF₃^–.

To complete the representation, draw square brackets around the entire Lewis structure and place a “-” or “-1” sign as a superscript outside the upper right bracket. This notation signifies that the negative charge is a property of the whole ion.

Next: CCl₂ Lewis structure

External links

• https://oneclass.com/homework-help/chemistry/7032645-cf3-lewis-structure.en.html
• https://www.chegg.com/homework-help/questions-and-answers/consider-cf3-draw-lewis-structure-molecule-resonance-also-draw-favourable-lewis-structures-q13556813