CH3CN 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.

CH3CN lewis structure has 2 Carbon atoms (C) at the center which are surrounded by three Hydrogen atoms (H) and one Nitrogen atom (N). There is a triple bond between the Carbon atom (C) and Nitrogen atom (N). There is 1 lone pair on the Nitrogen atom (N).

If you haven’t understood anything from the above image of CH3CN lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of CH3CN molecule.

So let’s move to the steps of drawing the lewis structure of CH3CN.

Steps of drawing CH3CN lewis structure

Step 1: Find the total valence electrons in CH3CN

In order to find the total valence electrons in a CH3CN molecule, first of all you should know the valence electrons present in carbon atom, hydrogen atom as well as nitrogen 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, hydrogen as well as nitrogen using a periodic table.

Total valence electrons in CH3CN 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.

→ Valence electrons given by nitrogen atom:

Nitrogen is a group 15 element on the periodic table. ^[3] Hence the valence electrons present in nitrogen is 5.

You can see the 5 valence electrons present in the nitrogen atom as shown in the above image.

Hence, 

Total valence electrons in CH3CN molecule = valence electrons given by 2 carbon atoms + valence electrons given by 3 hydrogen atoms + valence electrons given by 1 nitrogen atom = 4(2) + 1(3) + 5 = 16.

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 a CH3CN and it contains carbon atoms (C), hydrogen atoms (H) and nitrogen atoms (N).

So as per the rule we have to keep hydrogen outside.

Now, you can see the electronegativity values of carbon atom (C) and nitrogen atom (N) in the above periodic table.

If we compare the electronegativity values of carbon (C) and nitrogen (N) then the carbon atom is less electronegative.

So here the carbon atoms (C) are the center atom and the nitrogen atom (N) is the outside atom.

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

Now in the CH3CN molecule, you have to put the electron pairs between the carbon (C) atom, nitrogen (N) atom and hydrogen (H) atoms.

This indicates that these atoms are chemically bonded with each other in a CH3CN 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 CH3CN molecule, you can see that the outer atoms are hydrogen atoms and nitrogen atom.

These hydrogen atoms and nitrogen atom are forming a duplet and octet respectively and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the CH3CN molecule.

The CH3CN molecule has a total 16 valence electrons and all these valence electrons are used in the above sketch.

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. If it does not have octet, then shift the lone pair to form a double bond or triple bond.

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

In order to check the stability of the central carbon (C) atom, we have to check whether it is forming an octet or not.

Unfortunately, the carbon atom is not forming an octet here. Carbon has only 4 electrons and it is unstable.

Now to make this carbon atom stable, you have to shift the electron pair from the outer nitrogen atom so that the carbon atom can have 8 electrons (i.e octet).

But after shifting one electron pair, the carbon atom is still not forming an octet as it has only 6 electrons. 

So again we have to shift one more electron pair from the nitrogen atom only.

After shifting this electron pair, the central carbon atom will get 2 more electrons and thus its total electrons will become 8.

You can see from the above picture that the carbon atom is forming an octet.

And hence the carbon atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of CH3CN 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 CH3CN.

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 hydrogen (H) atom, carbon (C) atom as well as nitrogen (N) atoms present in the CH3CN 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 CH3CN molecule in the image given below.

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

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

For Nitrogen (N) atom:
Valence electrons = 5 (because nitrogen is in group 15)
Bonding electrons = 6
Nonbonding electrons = 2

Formal charge	=	Valence electrons	–	(Bonding electrons)/2	–	Nonbonding electrons
H	=	1	–	2/2	–	0	=	0
C	=	4	–	8/2	–	0	=	0
N	=	5	–	6/2	–	2	=	0

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

This indicates that the above lewis structure of CH3CN is stable and there is no further change in the above structure of CH3CN.

In the above lewis dot structure of CH3CN, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of CH3CN.

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:

SF3- Lewis Structure	CH3Br Lewis Structure
CH3OCH3 Lewis Structure	HCOOH (Formic acid) Lewis Structure
IF3 Lewis Structure	XeO4 Lewis Structure