C3H8 (propane) has three carbon atoms and eight hydrogen atoms. In the lewis structure of C3H8, there are two single bonds between the three carbon atoms. The left carbon and right carbon are attached with three hydrogen atoms, and the center carbon is attached with two hydrogen atoms. And none of the atoms has a lone pair.
Here’s how you can draw the C3H8 lewis structure step by step.
Step #1: draw sketch
Step #2: mark lone pairs (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 C3H8 has three carbon atoms and eight hydrogen atoms, so…
Valence electrons of three carbon atoms = 4 × 3 = 12
Valence electrons of eight hydrogen atoms = 1 × 8 = 8
And the total valence electrons = 12 + 8 = 20
- Second, find the total electron pairs
We have a total of 20 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 = 20 ÷ 2 = 10
- 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 three atoms remaining and all three atoms are carbon, so we can assume any one as the central atom.
Let’s assume that the central atom is center 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 10 electron pairs. And ten bonds are already marked. So we do not have to mark any electron pair as a lone pair on the sketch.
And in the above structure, you can see that the central atom (center carbon) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of C3H8.
Next: CH3CN Lewis Structure