Lewis Structure of CN- (With 6 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of CN- ion?

Awesome!

Here, I have explained 6 simple steps to draw the lewis dot structure of CN- ion (along with images).

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of CN- ion (or Cyanide ion) contains one triple bond between the Carbon (C) atom and Nitrogen (N) atom. The Carbon atom and Nitrogen atom, both have one lone pair. And the carbon atom has -1 formal charge.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of CN-).

6 Steps to Draw the Lewis Structure of CN-

Step #1: Calculate the total number of valence electrons

Here, the given molecule is CN- (cyanide ion). In order to draw the lewis structure of CN- ion, first of all you have to find the total number of valence electrons present in the CN- ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in CN-

• For Carbon:

Carbon is a group 14 element on the periodic table. ^[1]

Hence, the valence electrons present in carbon is 4 (see below image).

• For Nitrogen:

Nitrogen is a group 15 element on the periodic table. ^[2]

Hence, the valence electrons present in nitrogen is 5 (see below image).

Hence in a CN- ion, 

Valence electrons given by Carbon (C) atom = 4
Valence electrons given by Nitrogen (N) atom = 5
Electron due to -1 charge, 1 more electron is added
So, total number of Valence electrons in CN- molecule = 4 + 5 + 1 = 10

Step #2: Select the center atom

While selecting the atom, you have to put the least electronegative atom at the center. 

But here in the CN- ion, there are only two atoms. So you can consider any of the atoms as a center atom.

So, let’s assume that the carbon atom is a central atom. (You should assume the less electronegative atom as a central atom.)

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of CN molecule, put the two electrons (i.e electron pair) between the carbon atom and nitrogen atom to represent a chemical bond between them.

This pair of electrons present between the Carbon (C) atom and Nitrogen (N) atom forms a chemical bond, which bonds both the carbon atom and nitrogen atom with each other in a CN- ion.

Step #4: Complete the octet (or duplet) on outside atom. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of CN- ion, we have just assumed the carbon atom as a central atom and so the nitrogen atom is an outer atom.

So now, we have to complete the octet on this nitrogen atom.

Now, you can see in the above image that the nitrogen atom forms an octet.

Also, only 8 valence electrons of CN- ion are used in the above structure.

But there are total 10 valence electrons in CN- ion (as calculated in step #1).

So the number of electrons left to be kept on the central atom = 10 – 8 = 2.

So let’s keep these two electrons (i.e electron pair) on the central atom (i.e carbon atom).

Now, let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

In this step, we have to check whether the central atom (i.e carbon atom) has an octet or not.

In simple words, we have to check whether this Carbon (C) atom is having 8 electrons or not.

As you can see from the above image, this carbon atom has only 4 electrons. So it does not fulfill the octet rule.

Now, in order to fulfill the octet of this carbon atom, we have to move the electron pair from the outer atom (i.e nitrogen atom) to form a double bond.

Still, the octet of carbon atom is not fulfilled as it has only 6 electrons.

So again moving the electron pair from the nitrogen atom, we will get the following structure.

Now you can see from the above image that the carbon atom as well as nitrogen atom has 8 electrons. So both the atoms fulfill the octet rule and hence the above lewis structure of CN- ion is stable.

Step #6: Check the formal charge

Now, you have come to the final step and here you have to check the formal charge on CN molecule. 

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

• For Carbon:
  Valence electrons = 4 (as it is in group 14)
  Nonbonding electrons = 2
  Bonding electrons = 6
• For Nitrogen:
  Valence electron = 5 (as it is in group 15)
  Nonbonding electrons = 2
  Bonding electrons = 6

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

Let’s keep these charges on the atoms in the above lewis structure of CN- ion.

As you can see in the above sketch, there is one -ve charge on the carbon atom, which indicates the -1 formal charge on the CN molecule.

Hence, the above lewis structure of CN- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of CN- ion represents the single bond ( | ). So the above lewis dot structure of CN- ion can also be represented as shown below.

Related lewis structures for your practice:
Lewis structure of PF3
Lewis structure of PCl5
Lewis structure of H2O2
Lewis structure of F2
Lewis structure of CH2Cl2

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