Lewis structure of HNO2

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The Lewis structure of HNO₂ contains two single bonds and one double bond, with nitrogen in the center, and hydrogen and two oxygens on either side. There are two lone pairs on each oxygen atom, one lone pair on the nitrogen atom, and the hydrogen atom does not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of HNO₂.

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

Now HNO₂ has one hydrogen atom, one nitrogen atom, and two oxygen atoms.

So the total number of valence electrons = valence electrons of hydrogen atom + valence electrons of nitrogen atom + (valence electrons of oxygen atom × 2)

Therefore, the total number of valence electrons = 1 + 5 + 12 = 18

• 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 nitrogen and oxygen.

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

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

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

So now, put nitrogen in the center and hydrogen and oxygen on either side. And draw the rough skeleton structure for the Lewis structure of HNO₂ something like this:

Also read: How to draw Lewis structure of I₂ (4 steps)

#2 Show chemical bond

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

#3 Mark lone pairs

As calculated earlier, we have a total of 18 valence electrons. And in the above structure, we have already used six valence electrons. Hence, twelve valence electrons are remaining.

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

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

So right oxygen will get three lone pairs, and left oxygen will get two lone pairs. And the central atom (nitrogen) will get one lone pair.

Now draw the Lewis structure of HNO₂ something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (nitrogen) 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 C₃H₈ (3 steps)

#4 Complete octet on central atom

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

Now nitrogen already has six valence electrons. Hence, nitrogen needs two more valence electrons to complete its octet.

So convert one lone pair from the right oxygen atom to make a new bond with the nitrogen atom. And then, the Lewis structure of HNO₂ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (nitrogen), 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 IF₄^– (4 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 nitrogen atom

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

Formal charge = 5 – 2 – ½ (6) = 0

• For left oxygen and right oxygen atom

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

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of HNO₂ 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 HNO₂.

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

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Related

• Lewis structure of I₂
• Lewis structure of C₃H₈
• Lewis structure of IF₄^–
• Lewis structure of ICl₃
• Lewis structure of ClF₅

External links

• HNO2 Lewis Structure in 6 Steps (With Images) – Pediabay
• HNO2 (Nitrous acid) Lewis Structure – Chemistry School
• Drawing the Lewis Structure for HNO2 – The Geoexchange
• HNO2 Lewis Structure, Molecular Geometry, Hybridization, and Polarity – Techiescientist
• HNO2 Lewis Structure, Molecular Geometry, Hybridization, Bond Angle, and Shape – Geometry of Molecules
• HNO2 Lewis structure, molecular geometry, hybridization, polar or nonpolar – Topblogtenz
• How to Draw the Lewis Structure for Nitrous Acid – Pearson
• How would you draw a Lewis structure for HNO2? – Quora
• How many valence electrons are in the Lewis structure of HNO₂? – Homework.Study.com
• HNO2 Lewis structure, molecular geometry, hybridization, polar or nonpolar – Pinterest
• Why does HNO2 not have resonance? – Chemistry Stack Exchange
• Choose the best Lewis structure of HNO2 – Chegg
• Draw the Lewis structure of nitrous acid (HNO2) – Bartleby
• Draw the Lewis dot structure of Nitrous Acid (HNO2) – Numerade
• What is the lewis structure of HNO2? – OneClass
• Draw the Lewis dot structure for nitrous acid (HNO₂) – Quizlet