HNO Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

HNO lewis structure has a Nitrogen atom (N) at the center which is surrounded by one Hydrogen atom (H) and one Nitrogen atom (N). There is a double bond between the Nitrogen (N) & Oxygen (O) atom and a single bond between the Nitrogen (N) & Hydrogen (H) atom.

If you haven’t understood anything from the above image of HNO lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of HNO.

So let’s move to the steps of drawing the lewis structure of HNO.

Steps of drawing HNO lewis structure

Step 1: Find the total valence electrons in HNO molecule

In order to find the total valence electrons in a HNO molecule, first of all you should know the valence electrons present in hydrogen atom, nitrogen atom as well as oxygen atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of hydrogen, nitrogen as well as oxygen using a periodic table.

Total valence electrons in HNO molecule

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[1] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

→ Valence electrons given by nitrogen atom:

Nitrogen is a group 15 element on the periodic table. ^[2] Hence the valence electrons present in nitrogen is 5.

You can see the 5 valence electrons present in the nitrogen atom as shown in the above image.

→ Valence electrons given by oxygen atom:

Oxygen is group 16 element on the periodic table. ^[3] Hence the valence electrons present in oxygen is 6.

You can see the 6 valence electrons present in the oxygen atom as shown in the above image.

Hence, 

Total valence electrons in HNO molecule = valence electrons given by 1 hydrogen atom + valence electrons given by 1 nitrogen atom + valence electrons given by 1 oxygen atom = 1 + 5 + 6 = 12.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given molecule is HNO and it contains hydrogen atom (H), nitrogen atom (N) and oxygen atom (O).

So as per the rule we have to keep hydrogen outside.

Now, you can see the electronegativity values of nitrogen atom (N) and oxygen atom (O) in the above periodic table.

If we compare the electronegativity values of nitrogen atom (N) and oxygen atom (O) then the nitrogen atom is less electronegative.

So here the nitrogen atom is the center atom and the oxygen atom is the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the HNO molecule, you have to put the electron pairs between the hydrogen (H) & nitrogen (N) atom and between the nitrogen (N) & oxygen (O) atom.

This indicates that these atoms are chemically bonded with each other in a HNO molecule.

Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of HNO molecule, you can see that the outer atoms are hydrogen atom and oxygen atom.

These hydrogen and oxygen atoms are forming a duplet and octet respectively and hence they are stable.

Also, in step 1 we have calculated the total number of valence electrons present in the HNO molecule.

The HNO molecule has a total 12 valence electrons and out of these, only 10 valence electrons are used in the above sketch.

So the number of electrons which are left = 12 – 10 = 2.

You have to put these 2 electrons on the central nitrogen atom in the above sketch of HNO molecule.

Now let’s proceed to the next step.

Step 5: Check the octet on the central atom. If it does not have octet, then shift the lone pair to form a double bond or triple bond.

In this step, you have to check whether the central nitrogen atom (N) is stable or not.

In order to check the stability of the central nitrogen (N) atom, we have to check whether it is forming an octet or not.

Unfortunately, the nitrogen atom is not forming an octet here. Nitrogen has only 6 electrons and it is unstable.

Now to make this nitrogen atom stable, you have to shift the electron pair from the outer oxygen atom so that the nitrogen atom can have 8 electrons (i.e octet).

After shifting this electron pair, the central nitrogen atom will get 2 more electrons and thus its total electrons will become 8.

You can see from the above picture that the nitrogen atom is forming an octet as it has 8 electrons.

Now let’s proceed to the final step to check whether the lewis structure of HNO is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of HNO.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on hydrogen (H) atom, nitrogen (N) atom as well as oxygen (O) atom present in the HNO molecule.

For calculating the formal charge, you have to use the following formula;

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

You can see the number of bonding electrons and nonbonding electrons for each atom of HNO molecule in the image given below.

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

For Nitrogen (N) atom:
Valence electrons = 5 (because nitrogen is in group 15)
Bonding electrons = 6
Nonbonding electrons = 2

For Oxygen (O) atom:
Valence electrons = 6 (because oxygen is in group 16)
Bonding electrons = 4
Nonbonding electrons = 4

From the above calculations of formal charge, you can see that the hydrogen (H) atom, nitrogen (N) atom as well as oxygen (O) atom have a “zero” formal charge.

This indicates that the above lewis structure of HNO is stable and there is no further change in the above structure of HNO.

In the above lewis dot structure of HNO, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of HNO.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

About author

Jay Rana

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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