C6H6 (benzene) has six carbon atoms and six hydrogen atoms. In the lewis structure of C6H6, there are three single bonds and three double bonds between the six carbon atoms, and each carbon is attached with one hydrogen atom. And none of the atoms has a lone pair.
Here’s how you can draw the C6H6 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 and hydrogen has one valence electron.
Since C6H6 has six carbon atoms and six hydrogen atoms, so…
Valence electrons of six carbon atoms = 4 × 6 = 24
Valence electrons of six hydrogen atoms = 1 × 6 = 6
And the total valence electrons = 24 + 6 = 30
- Second, find the total electron pairs
We have a total of 30 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 = 30 ÷ 2 = 15
- 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 there are six atoms remaining and all six atoms are carbon, so we can assume any one as the central atom.
Let’s assume that the central atom is top carbon.
Therefore, place carbons in the center and hydrogens on either side.
- And finally, draw the rough sketch
#2 Mark Lone Pairs
Here, we have a total of 15 electron pairs. And twelve bonds are already marked. So we have to only mark the remaining three electron pairs as lone pairs on the sketch.
Also remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its 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 hydrogens, left carbons, right carbons, and bottom carbon. But no need to mark on hydrogen, because each hydrogen has already two electrons.
So for each left carbon, there is one lone pair, and for one right carbon, there is one lone pair, and for remaining carbons, there is zero lone pair because all three 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 top carbon, bottom carbon, and bottom right carbon atom, formal charge = 4 – 0 – ½ (6) = +1
For each left carbon and top right carbon atom, formal charge = 4 – 2 – ½ (6) = -1
For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0
Here, the carbon atoms have charges, so mark them on the sketch as follows:
The above structure is not a stable lewis structure because the carbon atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.
#4 Minimize Charges
Convert a lone pair of the top left carbon atom to make a new C — C bond with the top carbon atom as follows:
#5 Minimize Charges Again
Since there are charges on the carbon atoms, again convert a lone pair of the top right carbon atom to make a new C — C bond with the bottom right carbon atom as follows:
#6 Minimize Charges Again
There are still charges on the carbon atoms, so again convert a lone pair of the bottom left carbon atom to make a new C — C bond with the bottom carbon atom as follows:
In the above structure, you can see that the central atom (top 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 C6H6.
Next: NBr3 Lewis Structure