CF3Cl (chlorotrifluoromethane) has one carbon atom, three fluorine atoms, and one chlorine atom. In the lewis structure of CF3Cl, there are four single bonds around the carbon atom, with three fluorine atoms and one chlorine atom attached to it, and on each fluorine and chlorine atom, there are three lone pairs.
Here’s how you can draw the CF3Cl lewis structure step by step.
Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges (if there are)
Let’s break down each step in detail.
#1 Draw Sketch
- First, determine the total number of valence electrons
Hence, carbon has four valence electrons, both fluorine and chlorine have seven valence electrons.
Since CF3Cl has one carbon atom, three fluorine atoms, and one chlorine atom, so…
Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of three fluorine atoms = 7 × 3 = 21
Valence electrons of one chlorine atoms = 7 × 1 = 7
And the total valence electrons = 4 + 21 + 7 = 32
- Second, find the total electron pairs
We have a total of 32 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 = 32 ÷ 2 = 16
- Third, determine the central atom
We have to place the least electronegative atom at the center.
Since carbon is less electronegative than fluorine and chlorine, assume that the central atom is carbon.
Therefore, place carbon in the center and fluorine and chlorine on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 16 electron pairs. And four bonds are already marked. So we have to only mark the remaining twelve 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. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.
Always start to mark the lone pairs from outside atoms. Here, the outside atoms are fluorines and chlorines.
So for each fluorine and chlorine, there are three lone pairs, and for carbon, there is zero lone pair because all twelve electron pairs are over.
Mark the lone pairs on the sketch as follows:
#3 Mark Charges
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 – 0 – ½ (8) = 0
For each fluorine atom, formal charge = 7 – 6 – ½ (2) = 0
For each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, the atoms do not have charges, so no need to mark the charges.
And in the above structure, you can see that the central atom (carbon) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of CF3Cl.
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