Propane (C3H8) lewis dot structure, molecular geometry, polar or nonpolar, hybridization

Home Propane (C3H8) lewis structure 

C3H8 lewis structure molecular geometry

Propane appears as colorless gas at standard temperature and pressure. It has the chemical formula C3H8. Propane burns more easily than coal and gasoline.

In this article, we will discuss Propane (C3H8) lewis structure, molecular geometry, polar or nonpolar, its hybridization, etc.

Propane is also known as liquefied petroleum gas, it is generally odorless and non-toxic in nature. It has a role as a food propellant.

Name of MoleculePropane
Chemical formulaC3H8
Molecular geometry of C3H8Tetrahedral
HybridizationSp3
PolarityNonpolar molecule
Total Valence electron for C3H820

How to draw lewis structure of C3H8 (Propane)?

Propane (C3H8) Lewis structure contains three carbon atoms bonding with eight hydrogen atoms, all of these are bonded with the single bonds only. The lewis structure of C3H8 has 20 bonding electrons and zero non-bonding electrons.

The drawing of the Propane lewis structure is an easy and simple process.

Let’s see how to do it.

Follow some steps for drawing the lewis dot structure for C3H8

1. Count total valence electron in C3H8

Finding the total valence electrons in the molecule is our topmost priority for drawing the lewis diagram. Valence electrons are the outermost electrons of an atom that can help in the formation of the chemical bond.

Now we have to find the valence electron in the C3H8 molecule. To do this, look at the group number of carbon and hydrogen.

As the carbon atom belongs to group 14th in the periodic table and hydrogen is situated in the 1st group, hence, the valence electron for carbon is 4 and for the hydrogen atom, it is only 1.

⇒ Total number of the valence electrons in carbon = 4

⇒ Total number of the valence electrons in hydrogen = 1

∴ Total number of valence electron available for the C3H8 Lewis structure = 4(3) + 1(8) = 20 valence electrons         [∴ C3H8 molecule has three carbon and eight hydrogen atoms]

Total number of valence electron available for the C3H8 Lewis structure

2. Find the least electronegative atom and place it at center

An atom with a less electronegative value is preferable for the central position in the lewis diagram because they are more prone to share the electrons with surrounding atoms.

So, in the C3H8 molecule, two types of atoms are present – Hydrogen and Carbon. It should be noted that in the lewis diagram, hydrogen atoms always go outside means they always hold the place of the surrounding position, no matter what the situation is.

The hydrogen can never be the central atom since it can form a maximum of one covalent bond.

Therefore, place all three carbon atoms are in a central position and all eight hydrogens at surrounding to it as shown in the figure below.

central atom in C3H8 lewis structure

3. Connect outer atoms to central atom with a single bond

In the third step, draw a single bond to connect all outer atoms to the central atom.

So, in the case of the C3H8 molecule, place the single bond between each carbon and hydrogen atom. also, connect all three carbon atoms with each other by a single bond.

Propane lewis structure

That’s all, now count the valence electrons used in the above structure.

A single bond contains two electrons, and, in the above structure, 10 single bonds are used, hence, (10 × 2) = 20 valence electrons are used in the above structure.

We had a total of 20 valence electrons available for the C3H8 Lewis structure, and in the above structure, we used all 20 valence electrons.

∴ (20 – 20) = 0 valence electrons

So, we are left with 0 valence electrons.

4. Check the octet of all atoms

“The octet rule refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds.” [Exception may occur]

The hydrogen atom is an exception to the octet rule as it only needs two electrons to fulfill the outermost shell.

So, in the C3H8 molecule, there is hydrogen and carbon, the hydrogen atom needs only 2 electrons to fulfill the octet whereas the carbon prefers 8 electrons in its valence shell to attain stability.

C3H8 lewis structure

Propane (C3H8) Lewis structure

As you see in the above figure, all hydrogen attached with one single bond means they each have 2 electrons in their valence shell, hence, they completed their octet.

And each carbon atom is attached with 4 single bonds means they all have 8 electrons in their valence shell, hence, carbons atoms also completed their octet comfortably.

Hence, all the atoms in the above C3H8 lewis structure have a full octet, now we will check the formal charge for the above structure.

5. Check the stability with the help of a formal charge concept

The lesser the formal charge on atoms, the better is the stability of the lewis diagram.

To calculate the formal charge on an atom. Use the formula given below-

⇒ Formal charge = (valence electrons – nonbonding electrons –  1/2 bonding electrons)

Nonbonding electrons mean lone pair electrons, there is zero lone pair in the C3H8 Lewis structure.

Let’s count the formal charge on the hydrogen atom first, all hydrogen atoms in the C3H8 Lewis structure(4th step) have the same bonded electrons, so, just count the F.C. for the one hydrogen atom.

For hydrogen atom:

⇒ Valence electrons of hydrogen = 1

⇒ Nonbonding electrons on hydrogen= 0

⇒ Bonding electrons around hydrogen(1 single bond) = 2

∴ (1 – 0 – 2/2) = 0 formal charge on all hydrogen atoms.

 For carbon atom

⇒ Valence electrons of carbon = 4

⇒ Nonbonding electrons on carbon = 0

⇒ Bonding electrons around carbon (4 single bonds) = 8

∴ (4 – 0 – 8/2) = 0 formal charge on all carbon atoms.

Formal charge in Propane (C3H8) lewis structure

So, the above lewis structure of propane(C3H8) is the best and most stable as all atoms have formal charge zero.

What is the molecular geometry of C3H8 (Propane)?

The molecular geometry of C3H8 is tetrahedral with respect to a carbon atom since it is attached with four bonded pairs and contains no lone pair electrons, which means, it forms an AX4 type molecule.

A = central atom

X = Bonded pair attached to the Central atom

According to VSEPR theory or chart, the AX4 type molecule will form a tetrahedral geometry.

Molecular geometry or shape of C3H8 (propane)

Hybridization of C3H8

The hybridization concept was developed by Chemist Linus Pauling in 1931, he explain the concept of mixing atomic orbitals to form new hybrid orbitals.

Let’s find the hybridization of C3H8 through the steric number of its central atom.

“Steric number is the addition of a total number of bonded atoms around a central atom and the lone pair present on it.”

∴ Steric number of C3H8 = (Number of bonded atoms attached to carbon + Lone pair on carbon)

As per the lewis structure of C3H8, all three carbon central atoms is attached with 4 bonded pair and contain no lone pair of electrons. 

∴ Steric number of C3H8 = (4 + 0) = 4

Steric numberHybridization
1S
2Sp
3Sp²
4Sp³
5Sp³d
6Sp³d²

So, the hybridization of Propane (C3H8) is Sp3 for all three carbon atoms.

propane hybridization

Propane polarity: is C3H8 polar or nonpolar?

Is Propane (C3H8) polar or non-polar? Propane (C3H8) is a nonpolar molecule because the difference in electronegativity between carbon(2.55) and hydrogen(2.2) is less than 0.5, which is way lower to form a polar bond according to the Pauling scale. So, all the types of bonds in C3H8 such as C-H and C-C are nonpolar because of their low electronegativity difference which prevents the formation of dipole moment, resulting in the overall nonpolar Propane (C3H8) molecule.

Although, the carbon atom is slightly more electronegative than the hydrogen atom and this can generate a small dipole moment in it.

But the thing is, the carbon atom in the C3H8 molecule has a symmetrical tetrahedral geometrical shape which ensures that the dipole that will generate along the C-H bond will be easily canceled out, resulting in an overall nonpolar Propane (C3H8) molecule.

FAQ

How many bonding electrons are present in the C3H8 Lewis structure?

Bonding electrons that take part in the formation of bonds and are represented as single, double, or triple bonds between the atoms in the lewis diagram.

So, as per the C3H8 Lewis structure, there is only 10 single bonds are present means 10 bonded pair that contains 20 bonding electrons.

How many lone pair or nonbonding electrons are present in the propane lewis structure?

The nonbonding are lone pairs that do not take part in the formation of bonds and are represented as dots in the lewis diagram.

By looking at the C3H8 Lewis structure, we see there are no dots, all it has is single bonds that represent only bonding electrons.

So, in the Propane Lewis structure, the number of nonbonding or lone pair electrons is zero.

Also Read:

Properties of Propane

  • Its boiling point is −42.04 °C and its melting point is −187.7 °C.
  • It has an odor like faint petroleum.
  • It has a dipole moment of 0.083 D which is very low, hence, it is nonpolar in nature.
  • It can be compressible to a transportable liquid.
  • Propane is a member of liquefied petroleum gases (LP gases).
  • It burns more cleanly than gasoline and coal.
  • Mainly propane is produced by two processes, petroleum refining, and natural gas processing.
  • The vapors of Propane are heavier than air.

When propane undergoes a combustion reaction, it burns to form carbon dioxide and water molecules.

⇒ C3H8 + 5O2 → 3CO2 + 4H2O + Heat

When propane undergoes insufficient oxygen, it can form carbon monoxide and elemental carbon.

⇒ 2C3H8 + 9O2 → 4CO2 + 2CO + 8H2O + Heat

⇒ C3H8 + 2O2 → 3C + 4H2O + Heat

Uses of Propane

  1. It is used as fuel in domestic, transportation, and industries or factories.
  2. It is used in various film cities, theme parks, and movie production for special effects.
  3. One of the primary use of propane as the primary fuel for hot-air balloons.
  4. It is used as shipping fuel, motor fuel, and industrial fuel since the transportation of propane is easy.
  5. Since propane has a low boiling point, it is popular for portable stoves.

Facts about Propane

  • It is one of the environmentally-friendly fuels, hence, it does not cause long-term environmental damage.
  • The weight of water is twice as propane in liquid form.
  • It is one of the cleanest burnings of all fossil fuels.
  • Propane furnaces can be up to 95 percent efficient.
  • Propane is considered nontoxic in nature but long-term exposure can cause irritation.
  • To run the same appliance, propane requires less energy than electricity.

Summary

  • The total valence electron is available for drawing the Propane (C3H8) Lewis structure is 20.
  • The molecular geometry of C3H8 with respect to the carbon atom is tetrahedral.
  • The lewis structure of C3H8 has 10 bonding pairs and zero lone pairs.
  • All three carbon atoms in Propane (C3H8) forms Sp3 hybridization.
  • Propane (C3H8) is a nonpolar molecule because of the very low difference in electronegativity between the atoms which prevents the formation of dipole moment, resulting, in the overall nonpolar molecule.
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