What is the Charge on CN (Cyanide ion)? And Why?

The Charge of CN (Cyanide ion) is 1-.

But the question is how can you find the charge on CN (cyanide ion)?

Well there are 2 methods by which you can find the charge of CN.

Lets dive right into these methods one by one.

You can also refer to the below video from which you will learn to find charge of any ion.

Method 1: By looking at what it is bonded to

The charge of CN (Cyanide ion) can be found out by looking at what it is bonded to.

So let’s take some examples of compounds that contain CN; like HCN, KCN, etc.

Example 1: HCN
In HCN, the CN is bonded to Hydrogen (H).
You know that the ionic charge of H is 1+.
So you can easily say that the charge of CN should be 1-, then only it will get canceled out.
Hence the charge of CN in HCN is 1-.

Example 2: KCN
In KCN, the CN is bonded to Potassium (K).
And again, you know that the ionic charge of K is 1+.
So here also you can easily say that the charge of CN should be 1-, then only it will get canceled out.
Hence the charge of CN in KCN is 1-.

As seen from the above examples,
The charge of CN is 1-.

In this way, you can easily find the charge of CN by looking at what it is bonded to.

Method 2: By calculating the formal charge using lewis structure

In order to calculate the formal charge on CN (Cyanide ion), you should know the Lewis dot structure of CN (Cyanide ion).

Here is the lewis structure of CN.

Now using the above lewis structure of CN, you have to find the formal charge on each atom that is present in the CN molecule.

For calculating the formal charge, you need to remember this formula;

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

You can see the bonding and nonbonding electrons of CN from the image given below.

So now let’s calculate the formal charge on each individual atom present in CN.

Formal charge on Carbon atom:
Valence electrons = 4 (as it is in group 14 on periodic table) ^[1]
Nonbonding electrons = 2
Bonding electrons = 6

So according to the formula of formal charge, you will get;

Formal charge on Carbon = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 4 – 2 – (6/2) = 1-

So the formal charge on carbon atom is 1-.

Formal charge on Nitrogen atom:
Valence electron = 5 (as it is in group 15 on periodic table) ^[2]
Nonbonding electrons = 2
Bonding electrons = 6

So according to the formula of formal charge, you will get;

Formal charge on Nitrogen = Valence electrons – Nonbonding electrons – (Bonding electrons)/2 = 5 – 2 – (6/2) = 0

So the formal charge on nitrogen atom is 0.

Now let’s put all these charges on the lewis dot structure of CN.

So there is overall 1- charge left on the entire molecule.

This indicates that the CN (Cyanide ion) has 1- charge.

I hope you have understood the above calculations of CN (Cyanide ion). But for your tests, you don’t need to remember the entire calculations. You should just try to remember that CN has 1- charge.

Check out some other related topics for your practice.

Related topics:
Charge of Selenium (Se)
Charge of Vanadium (V)
Charge of Mercury (Hg)
Charge of Helium (He)
Charge of Gold (Au)