Lewis Structure of C3H8 (Propane) (In 6 Simple Steps)

Lewis structure of C3H8

Ready to learn how to draw the lewis structure of C3H8?


Here, I have explained 6 simple steps to draw the lewis dot structure of C3H8 (along with images).

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of C3H8 (or Propane) contains single bonds between Carbon-Carbon atoms as well as between Carbon-Hydrogen atoms. The three Carbon atoms (C) are at the center and they are surrounded by Hydrogen atoms (H).

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of C3H8).

6 Steps to Draw the Lewis Structure of C3H8

Step #1: Calculate the total number of valence electrons

Here, the given molecule is C3H8 (propane). In order to draw the lewis structure of C3H8, first of all you have to find the total number of valence electrons present in the C3H8 molecule.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in C3H8

  • For Carbon:

Carbon is a group 14 element on the periodic table. [1]

Hence, the valence electrons present in carbon is 4 (see below image).

  • For Hydrogen: 

Hydrogen is a group 1 element on the periodic table. [2]

Hence, the valence electron present in hydrogen is 1 (see below image).

Hence in a C3H8 molecule, 

Valence electrons given by Carbon (C) atom = 4
Valence electron given by each Hydrogen (H) atom = 1
So, total number of Valence electrons in C3H8 molecule = 4(3) + 1(8) = 20

Step #2: Select the center atom (H is always outside)

While selecting the center atom, always put the least electronegative atom at the center.

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). [3]

Here in the C3H8 molecule, if we compare the carbon atom (C) and hydrogen atom (H), then hydrogen is less electronegative than carbon. But as per the rule, we have to keep hydrogen outside.

So, all the 3 carbon atoms should be placed in the center and the remaining 8 hydrogen atoms will surround it.

step 1

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of C3H8 molecule, put the two electrons (i.e electron pair) between carbon-carbon atoms as well as between each carbon and hydrogen atom to represent a chemical bond between them.

step 2

These pairs of electrons present between the Carbon (C) and Hydrogen (H) atoms form a chemical bond, which bonds the carbon-carbon atom and carbon-hydrogen atoms in a C3H8 molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of C3H8, the outer atoms are hydrogen atoms.

So now, you have to check whether these hydrogen atoms are forming a duplet or not! (because hydrogen requires only 2 electrons to have a complete outer shell).

step 3

You can see in the above image that all the hydrogen atoms form a duplet.

Also, all the 20 valence electrons of C3H8 molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of C3H8.

Let’s move to the next step.

Step #5: Check whether the central atom has octet or not

In this step, we have to check whether the central atoms (i.e three carbon atoms) have an octet or not. 

In simple words, we have to check whether the central Carbon (C) atoms has 8 electrons or not.

step 4

As you can see from the above image, the central atoms (i.e carbon), has 8 electrons. So it fulfills the octet rule and all the carbon atoms are stable.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on each carbon atom (C) as well as each hydrogen atom (H).

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

step 5
  • For Carbon:
    Valence electrons = 4 (as it is in group 14)
    Nonbonding electrons = 0
    Bonding electrons = 8
  • For Hydrogen:
    Valence electron = 1 (as it is in group 1)
    Nonbonding electrons = 0
    Bonding electrons = 2
Formal charge=Valence electronsNonbonding electrons(Bonding electrons)/2

So you can see above that the formal charges on carbon as well as hydrogen are “zero”.

Hence, there will not be any change in the above structure and the above lewis structure of C3H8 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of C3H8 represents the single bond ( | ). So the above lewis dot structure of C3H8 can also be represented as shown below.

C3H8 Lewis structure

Related lewis structures for your practice:
Lewis Structure of CH3CN
Lewis Structure of SF3-
Lewis Structure of CH3Br
Lewis Structure of CH3OCH3
Lewis Structure of HCOOH (Formic acid) 

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Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. With a desire to make learning accessible for everyone, he founded Knords Learning, an online learning platform that provides students with easily understandable explanations.

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