Lewis structure of C3H8

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Lewis structure of C3H8
Lewis structure of C3H8 | Image: Root Memory

The Lewis structure of C3H8 contains ten single bonds, with three carbons in the center. The left carbon and right carbon are attached with three hydrogens, and center carbon is attached with two hydrogens. Both hydrogen atom and carbon atom do not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of C3H8.

#1 Draw skeleton
#2 Show chemical bond
#3 Calculate formal charge and check stability (if there are no lone pairs and octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw Skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… carbon is a group 14 element and hydrogen is a group 1 element. Hence, carbon has four valence electrons and hydrogen has one valence electron.

Now C3H8 has three carbon atoms and eight hydrogen atoms.

So the total number of valence electrons = (valence electrons of carbon atom × 3) + (valence electrons of hydrogen atom × 8)

Therefore, the total number of valence electrons = 12 + 8 = 20

  • Now decide the central atom

We can not assume hydrogen as 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.

Therefore, choose carbon as the central atom.

But there are three carbon atoms in C3H8. Hence, we can assume any one as the central atom. Let’s assume that center carbon is the central atom.

So now, put three carbons in the center and eight hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of C3H8 something like this:

Skeleton structure for Lewis structure of C3H8 | Image: Root Memory

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since three carbons are surrounded by eight hydrogens, use twenty electrons to show ten chemical bonds as follows:

Ten chemical bonds shown between atoms | Image: Root Memory

In the above structure, you can see that the octet is completed on the central atom (center carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#3 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

  • For each carbon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

  • For each hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of C3H8 looks something like this:

Formal charges are calculated, and got the stable Lewis structure of C3H8 | Image: Root Memory

In the above structure, you can see that the formal charges of both (carbon and hydrogen) are zero. Therefore, this is the stable Lewis structure of C3H8.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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