CHFO (formyl fluoride) has one carbon atom, one hydrogen atom, one fluorine atom, and one oxygen atom. In the lewis structure of CHFO, the hydrogen and fluorine atoms make two single bonds, and the oxygen atom makes one double bond with the carbon atom. The oxygen atom has two lone pairs, and the fluorine atom has three lone pairs.
Here’s how you can draw the CHFO lewis structure step by step.
Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges
Step #4: minimize charges
Step #5: minimize charges again (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, hydrogen has one valence electron, fluorine has seven valence electrons, and oxygen has six valence electrons.
Since CHFO has one carbon atom, one hydrogen atom, one fluorine atom, and one oxygen atom, so…
Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of one hydrogen atom = 1 × 1 = 1
Valence electrons of one fluorine atom = 7 × 1 = 7
Valence electrons of one oxygen atom = 6 × 1 = 6
And the total valence electrons = 4 + 1 + 7 + 6 = 18
- Second, find the total electron pairs
We have a total of 18 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 = 18 ÷ 2 = 9
- Third, determine the central atom
Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.
Now we have to choose the central atom from carbon, fluorine, and oxygen. Place the least electronegative atom at the center.
Since carbon is less electronegative than fluorine and oxygen, assume that the central atom is carbon.
Therefore, place carbon in the center and hydrogen, fluorine, and oxygen on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 9 electron pairs. And three bonds are already marked. So we have to only mark the remaining six electron pairs as lone pairs on the sketch.
Also remember that all three (carbon, fluorine, and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.
Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogen, fluorine, and oxygen. But no need to mark on hydrogen, because hydrogen already has two electrons.
So for fluorine and oxygen, there are three lone pairs, and for carbon, there is zero lone pair because all six 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 (6) = +1
For hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0
For fluorine atom, formal charge = 7 – 6 – ½ (2) = 0
For oxygen atom, formal charge = 6 – 6 – ½ (2) = -1
Here, both carbon and oxygen atoms have charges, so mark them on the sketch as follows:
The above structure is not a stable lewis structure because both carbon and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.
#4 Minimize Charges
Convert a lone pair of the oxygen atom to make a new C — O bond with the carbon atom as follows:
In the above structure, you can see that the central atom (carbon) forms 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 CHFO.
Next: Cr2O72- Lewis Structure