C2F2 Lewis structure - Learnool (2024)

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C₂F₂ (difluoroacetylene) has two carbon atoms and two fluorine atoms.

In the C₂F₂ Lewis structure, there is a triple bond between the two carbon atoms, and each carbon is attached with one fluorine atom, and on each fluorine atom, there are three lone pairs.

Steps

To properly draw the C₂F₂ Lewis structure, follow these steps:

#1 Draw a rough sketch of the structure
#2 Next, indicate lone pairs on the atoms
#3 Indicate formal charges on the atoms, if necessary
#4 Minimize formal charges by converting lone pairs of the atoms
#5 Repeat step 4 if necessary, until all charges are minimized

Let’s break down each step in more detail.

#1 Draw a rough sketch of the structure

• 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 C₂F₂ has two carbon atoms and two fluorine atoms, so…

Valence electrons of two carbon atoms = 4 × 2 = 8
Valence electrons of two fluorine atoms = 7 × 2 = 14

And the total valence electrons = 8 + 14 = 22

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

• Second, find the total electron pairs

We have a total of 22 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 = 22 ÷ 2 = 11

• 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.

Here, there are two carbon atoms, so we can assume any one as the central atom.

Let’s assume that the central atom is right carbon.

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

• And finally, draw the rough sketch

#2 Next, indicate lone pairs on the atoms

Here, we have a total of 11 electron pairs. And three bonds are already marked. So we have to only mark the remaining eight 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 and left carbon.

So for each fluorine, there are three lone pairs, for left carbon, there are two lone pairs, and for right carbon, there is zero lone pair because all eight electron pairs are over.

Mark the lone pairs on the sketch as follows:

#3 Indicate formal charges on the atoms, if necessary

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

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

For left carbon atom, formal charge = 4 – 4 – ½ (4) = -2

For right carbon atom, formal charge = 4 – 0 – ½ (4) = +2

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

Here, both carbon atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both carbon atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

#4 Minimize formal charges by converting lone pairs of the atoms

Convert a lone pair of the left carbon atom to make a new C — C bond with the right carbon atom as follows:

#5 Repeat step 4 (minimize charges again)

Since there are charges on both carbon atoms, again convert a lone pair of the left carbon atom to make a new C — C bond with the right carbon atom as follows:

In the above structure, you can see that the central atom (right carbon) forms an octet. And the outside atoms (left carbon and fluorines) also form an octet. Hence, the octet rule is satisfied.

Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable Lewis structure of C₂F₂.

Next: C2Cl2 Lewis structure

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