Lewis structure of HOCN

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The Lewis structure of HOCN contains two single bonds and one triple bond, with carbon in the center, and hydrogen, oxygen, and nitrogen on either side. The oxygen atom has two lone pairs, the nitrogen atom has one lone pair, and hydrogen atom and carbon atom do not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of HOCN.

#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… hydrogen is a group 1 element, oxygen is a group 16 element, carbon is a group 14 element, and nitrogen is a group 15 element. Hence, hydrogen has one valence electron, oxygen has six valence electrons, carbon has four valence electrons, and nitrogen has five valence electrons.

Now HOCN has one hydrogen atom, one oxygen atom, one carbon atom, and one nitrogen atom.

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

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

• Now decide the central atom

We can not assume hydrogen as 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.

Therefore, choose the central atom from oxygen, carbon, and nitrogen.

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 hydrogen, oxygen, and nitrogen on either side. And draw the rough skeleton structure for the Lewis structure of HOCN something like this:

Also read: How to draw Lewis structure of SF₅^– (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by hydrogen, oxygen, and nitrogen, use six electrons to show three 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 six valence electrons. Hence, ten valence electrons are remaining.

Two valence electrons represent one lone pair. So ten valence electrons = five lone pairs.

Note that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And 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 hydrogen, oxygen, and nitrogen. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So nitrogen will get three lone pairs, and oxygen will get two lone pairs. And the central atom (carbon) will not get any lone pair, because all five lone pairs are used.

Now draw the Lewis structure of HOCN something like this:

In the above structure, you can see that the octet is completed on outside atoms. 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 SeF₂ (4 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 HOCN 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 NO₄^3- (5 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 hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

• For oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

• 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 HOCN looks something like this:

In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of HOCN.

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

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Related

• Lewis structure of SF₅^–
• Lewis structure of SeF₂
• Lewis structure of NO₄^3-
• SF₃⁺ Lewis structure
• Lewis structure of C₂Cl₂

External video

• HOCN Lewis Structure: How to Draw the Lewis Structure for HOCN – Wayne Breslyn

External links

• HOCN Lewis Structure in 6 Steps (With Images) – Pediabay
• Draw the Lewis dot structure for HOCN, CF2Cl2, SeF6, H2CO – Homework.Study.com
• Draw a Lewis structure for cyanic acid, HOCN , adding charges and lone electron pairs to the appropriate atoms – Chegg
• Write Lewis structures and predict whether each of the following is polar or nonpolar. HOCN (exists as HOOCN) – Quizlet
• Draw the most important Lewis structure for the HOCN molecule – Numerade
• What is the lewis structure of HOCN? Is it polar or nonpolar? – OneClass