C3H6 Lewis structure

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C₃H₆ (propene) has three carbon atoms and six hydrogen atoms.

In the C₃H₆ Lewis structure, there is one double bond and one single bond between the three carbon atoms. The left carbon is attached with two hydrogen atoms, the center carbon is attached with one hydrogen atom, and the right carbon is attached with three hydrogen atoms. And none of the atoms has a lone pair.

Steps

To properly draw the C₃H₆ 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 hydrogen lies in group 1.

Hence, carbon has four valence electrons and hydrogen has one valence electron.

Since C₃H₆ has three carbon atoms and six hydrogen atoms, so…

Valence electrons of three carbon atoms = 4 × 3 = 12
Valence electrons of six hydrogen atoms = 1 × 6 = 6

And the total valence electrons = 12 + 6 = 18

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

• 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 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 Next, indicate lone pairs on the atoms

Here, we have a total of 9 electron pairs. And eight bonds are already marked. So we have to only mark the remaining one electron pair as a lone pair 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 carbon, and right carbon. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for left carbon, there is one lone pair, and for other two carbons, there is zero lone pair because all 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 – 2 – ½ (6) = -1

For center carbon atom, formal charge = 4 – 0 – ½ (6) = +1

For right carbon atom, formal charge = 4 – 0 – ½ (8) = 0

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

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

The above structure is not a stable Lewis structure because both left carbon and center 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 center carbon atom as follows:

In the above structure, you can see that the central atom (center carbon) forms an octet. The outside atoms (left carbon and right carbon) also form an octet, and all hydrogens form a duet. Hence, the octet rule and duet rule are satisfied.

Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable Lewis structure of C₃H₆.

Next: HOCl Lewis structure

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External links

• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/C3H6-lewis-structure.html
• https://topblogtenz.com/propene-c3h6-lewis-structure-molecular-geometry-polar-or-nonpolar-hybridization/