C3H8 (Propane) Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

C3H8 (Propane) lewis structure has a single bond between the Carbon-Carbon atoms (C) as well as between the Carbon atom (C) and Hydrogen atom (H). The three Carbon atoms (C) are at the center and they are surrounded by the Hydrogen atoms (H).

If you haven’t understood anything from the above image of C3H8 lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of C3H8.

So let’s move to the steps of drawing the lewis structure of C3H8.

Steps of drawing C3H8 lewis structure

Step 1: Find the total valence electrons in C3H8 molecule

In order to find the total valence electrons in a C3H8 molecule, first of all you should know the valence electrons present in carbon atom as well as hydrogen atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of carbon as well as hydrogen using a periodic table.

Total valence electrons in C3H8 molecule

→ Valence electrons given by carbon atom:

Carbon is group 14 element on the periodic table. ^[1] Hence the valence electrons present in carbon is 4.

You can see the 4 valence electrons present in the carbon atom as shown in the above image.

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[2] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

Hence, 

Total valence electrons in C3H8 molecule = valence electrons given by 3 carbon atom + valence electrons given by 8 hydrogen atoms = 4(3) + 1(8) = 20.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given molecule is C3H8 (or propane) and it contains carbon atoms (C) and hydrogen atoms (H).

You can see the electronegativity values of carbon atom (C) and hydrogen atom (H) in the above periodic table.

If we compare the electronegativity values of carbon (C) and hydrogen (H) then the hydrogen atom is less electronegative. But as per the rule we have to keep hydrogen outside.

So here all three carbon atoms (C) are the center atom and the hydrogen atoms (H) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the C3H8 molecule, you have to put the electron pairs between the carbon-carbon atoms and between the carbon-hydrogen atoms.

This indicates that these atoms are chemically bonded with each other in a C3H8 molecule.

Step 4: Make the outer atoms stable

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of C3H8 molecule, you can see that the outer atoms are hydrogen atoms.

These outer hydrogen atoms are forming a duplet and hence they are stable. 

Also, in step 1 we have calculated the total number of valence electrons present in the C3H8 molecule.

The C3H8 molecule has a total 20 valence electrons and all these valence electrons are used in the above sketch of C3H8. 

Hence there are no remaining electron pairs to be kept on the central atoms. 

So now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central carbon atoms (C) are stable or not.

In order to check the stability of the central carbon (C) atoms, we have to check whether they are forming an octet or not.

You can see from the above picture that all three carbon atoms are forming an octet. That means they have 8 electrons.

And hence the central carbon atoms are stable.

Now let’s proceed to the final step to check whether the lewis structure of C3H8 is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of C3H8.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on carbon (C) atoms as well as hydrogen (H) atoms present in the C3H8 molecule.

For calculating the formal charge, you have to use the following formula;

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

You can see the number of bonding electrons and nonbonding electrons for each atom of C3H8 molecule in the image given below.

For Carbon (C) atom:
Valence electrons = 4 (because carbon is in group 14)
Bonding electrons = 8
Nonbonding electrons = 0

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

From the above calculations of formal charge, you can see that the carbon (C) atoms as well as hydrogen (H) atoms have a “zero” formal charge.

This indicates that the above lewis structure of C3H8 is stable and there is no further change in the above structure of C3H8.

In the above lewis dot structure of C3H8, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of C3H8.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

About author

Jay Rana

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. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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