CH3NH2 Lewis structure

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CH3NH2 Lewis Structure
CH3NH2 Lewis structure

CH3NH2 (methylamine) has one carbon atom, five hydrogen atoms, and one nitrogen atom.

In the CH3NH2 Lewis structure, there is a single bond between the carbon and nitrogen atom. The carbon atom is attached with three hydrogen atoms, and the nitrogen atom is attached with two hydrogen atoms. And on the nitrogen atom, there is one lone pair.


Use these steps to correctly draw the CH3NH2 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
Periodic table

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 CH3NH2 has one carbon atom, five hydrogen atoms, and one nitrogen atom, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of five hydrogen atoms = 1 × 5 = 5
Valence electrons of one nitrogen atom = 5 × 1 = 5

And the total valence electrons = 4 + 5 + 5 = 14

  • Second, find the total electron pairs

We have a total of 14 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 = 14 ÷ 2 = 7

  • 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.

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

  • And finally, draw the rough sketch
CH3NH2 Lewis Structure (Step 1)
Rough sketch of CH3NH2 Lewis structure

#2 Mark lone pairs on the atoms

Here, we have a total of 7 electron pairs. And six 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 and nitrogen. But no need to mark on hydrogen, because each hydrogen has already two electrons.

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

Mark the lone pairs on the sketch as follows:

CH3NH2 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of CH3NH2

#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 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 (carbon) forms an octet. The outside atom (nitrogen) also forms 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 CH3NH2.

Next: SiO2 Lewis structure

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