C8H18 Lewis structure

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C₈H₁₈ (octane) has eight carbon atoms and eighteen hydrogen atoms.

In C₈H₁₈ Lewis structure, there are seven single bonds between the eight carbon atoms. The first carbon and last carbon are attached with one carbon and three hydrogen atoms, and the remaining six carbons are attached with two hydrogen atoms. And none of the atoms has a lone pair.

Steps

Use these steps to correctly draw the C₈H₁₈ Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

• 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 C₈H₁₈ has eight carbon atoms and eighteen hydrogen atoms, so…

Valence electrons of eight carbon atoms = 4 × 8 = 32
Valence electrons of eighteen hydrogen atoms = 1 × 18 = 18

And the total valence electrons = 32 + 18 = 50

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

• Second, find the total electron pairs

We have a total of 50 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 = 50 ÷ 2 = 25

• 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 eight atoms remaining and all eight atoms are carbon, so we can assume any one as the central atom.

Let’s assume that the central atom is first carbon.

Therefore, place carbons in the center and hydrogens on either side.

• And finally, draw the rough sketch

#2 Mark lone pairs on the atoms

Here, we have a total of 25 electron pairs. And twenty-five bonds are already marked. So we do not have to mark any electron pair as a lone pair on the sketch.

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

Therefore, this structure is the stable Lewis structure of C₈H₁₈.

Next: P₂H₄ Lewis structure

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