# C3H9N Lewis structure

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C3H9N (propylamine) has three carbon atoms, nine hydrogen atoms, and one nitrogen atom.

In C3H9N Lewis structure, there are two single bonds between the three carbon atoms. The left carbon is attached with three hydrogen atoms, the center carbon is attached with two hydrogen atoms, and the right carbon is attached with one nitrogen atom and two hydrogen atoms. And the nitrogen atom (with which the other two hydrogen atoms are attached) has one lone pair.

Contents

## Steps

Use these steps to correctly draw the C3H9N 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, hydrogen lies in group 1, and nitrogen lies in group 15.

Hence, carbon has four valence electrons, hydrogen has one valence electron, and nitrogen has five valence electrons.

Since C3H9N has three carbon atoms, nine hydrogen atoms, and one nitrogen atom, so…

Valence electrons of three carbon atoms = 4 × 3 = 12
Valence electrons of nine hydrogen atoms = 1 × 9 = 9
Valence electrons of one nitrogen atom = 5 × 1 = 5

And the total valence electrons = 12 + 9 + 5 = 26

• Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

• 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 we have to choose the central atom from carbon and nitrogen. Place the least electronegative atom at the center.

Since carbon is less electronegative than nitrogen, assume that the central atom is carbon.

Here, there are three carbon atoms, so we can assume any one as the central atom.

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

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

• And finally, draw the rough sketch

### #2 Mark lone pairs on the atoms

Here, we have a total of 13 electron pairs. And twelve bonds are already marked. So we have to only mark the remaining one electron pair as a lone pair on the sketch.

Also remember that both (carbon and nitrogen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell. And hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens, nitrogen, left carbon, and right carbon. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for nitrogen, there is one lone pair, and for left carbon and right carbon, there is zero lone pair because all electron pairs are over.

Mark the lone pairs on the sketch as follows:

### #3 Calculate and mark formal charges on the atoms, if required

Use the following formula to calculate the formal charges on atoms:

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

For each carbon atom, formal charge = 4 – 0 – ½ (8) = 0

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

For nitrogen atom, formal charge = 5 – 2 – ½ (6) = 0

Here, the atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (center carbon) forms an octet. The outside atoms (nitrogen, left carbon, and right carbon) 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 C3H9N.