Lewis structure of OCN-

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The Lewis structure of OCN^– contains one single bond and one triple bond, with carbon in the center, and oxygen and nitrogen on either side. The oxygen atom has three lone pairs, the nitrogen atom has one lone pair, and the carbon atom does not have any lone pair.

Plus, there is a negative (-1) charge on the nitrogen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of OCN^–:

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… oxygen is a group 16 element, carbon is a group 14 element, and nitrogen is a group 15 element. Hence, oxygen has six valence electrons, carbon has four valence electrons, and nitrogen has five valence electrons.

Now OCN^– has one oxygen atom, one carbon atom, and one nitrogen atom.

So the total number of valence electrons = valence electrons of oxygen atom + valence electrons of carbon atom + valence electrons of nitrogen atom

And OCN^– has a negative (-1) charge, so we have to add one more electron.

Therefore, the total number of valence electrons = 6 + 4 + 5 + 1 = 16

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for oxygen, carbon, and nitrogen as follows:

Electronegativity value of oxygen = 3.44
Electronegativity value of carbon = 2.55
Electronegativity value of nitrogen = 3.04

Obviously, carbon is less electronegative than oxygen and nitrogen. Hence, assume that carbon is the central atom.

So now, put carbon in the center and oxygen and nitrogen on either side. And draw the rough skeleton structure for the Lewis structure of OCN^– something like this:

Also read: How to draw Lewis structure of CH₃F (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by oxygen and nitrogen, use four electrons to show two chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 16 valence electrons. And in the above structure, we have already used four valence electrons. Hence, twelve valence electrons are remaining.

Two valence electrons represent one lone pair. So twelve valence electrons = six lone pairs.

Note that all (oxygen, carbon, and nitrogen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are oxygen and nitrogen, so oxygen and nitrogen will get three lone pairs. And the central atom (carbon) will not get any lone pair, because all six lone pairs are used.

So the Lewis structure of OCN^– looks something like this:

In the above structure, you can see that the octet is completed on the outside atom. But, the central atom (carbon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of BrO₃^– (5 steps)

#4 Complete octet on central atom

Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now carbon already has four valence electrons. Hence, carbon needs four more valence electrons to complete its octet.

So convert two lone pairs from the nitrogen atom to make a new bond with the carbon atom. And then, the Lewis structure of OCN^– looks something like this:

Here, the lone pair of nitrogen is converted (instead of oxygen). This is because nitrogen is less electronegative than oxygen, and so it can give more electrons to share them.

In the above structure, you can see that the octet is completed on the central atom (carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of NH₄⁺ (3 steps)

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

• For carbon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For nitrogen atom

Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 5 – 2 – ½ (6) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of OCN^– looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of OCN^–.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

Now OCN^– is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of OCN^– looks something like this:

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Related

• Lewis structure of CH₃F
• Lewis structure of BrO₃^–
• Lewis structure of NH₄⁺
• Lewis structure of HNO
• Lewis structure of BeH₂

External video

• OCN- Lewis Structure: How to Draw the Lewis Structure for OCN- – YouTube • Wayne Breslyn

External links

• Drawing the Lewis Structure for OCN- (Cyanate ion) – The Geoexchange
• OCN- lewis structure, molecular geometry, hybridization, Polar or nonpolar – Topblogtenz
• What is the lewis structure for OCN – Socratic
• OCN- Lewis Structure in 6 Steps (With Images) – Pediabay
• Draw the appropriate Lewis structure corresponding to OCN – Homework.Study.com
• OCN- Lewis Structure: How to Draw the Lewis Structure for OCN- – Pinterest
• The cyanate ion, OCN , has three resonance structures – Chegg
• NCO Lewis Structure, Geometry, Hybridization, and Polarity – Techiescientist
• There are three possible Lewis structures for cyanate ion: OCN- – Numerade
• Write the Lewis structure for OCN? – Answers
• Draw the Lewis structure for the (OCN) ion – Bartleby
• Choose all resonance structures of ocn− with right formal charges in each – Brainly
• OCN- (Cyanate Anion) Oxidation Number – ChemicalAid
• NCO- Lewis Structure, Hybridization, Molecular Geometry and Shape – Geometry of Molecules
• Why is N central atom in CNO-? – Laurence Lavelle
• The Lewis structure for NCO – Chemistry Stack Exchange