MO Diagram, Molecular Geometry, Hybridization, and Lewis Structure of HNO3

A particularly significant chemical is nitric acid (HNO3), an extremely corrosive acid. It’s normally a colourless liquid, but when it decomposes into water and nitrogen oxides, older samples turn pale yellow.

The vapours from this hazardous liquid are yellow or red-brown in colour and can cause major eye and nose damage. Your skin will also be severely burned by the concentrated acid.

Ammonia can be oxidised to make this chemical.

Nitric acid is also known as aqua fortis and the spirit of niter. The chemical is utilised in a variety of industries, including paint, fertilisers, explosives, and a variety of other items.

It’s utilised in the production of ammonium nitrate fertiliser. HNO3 is a fascinating molecule to investigate.

The Lewis structure, molecular geometry, and hybridization of this acid will be discussed in the following sections.

Nitric Acid’s Lewis Structure (HNO3)

The chemical formula of nitric acid is HNO3, which indicates it has one hydrogen atom that forms bonds with the nitrate ion.

Let’s look at the electrical configurations of the atoms and how many electrons they have in the outermost shell to figure out the compound’s molecular structure.

The electrical configuration of the hydrogen atom is 1S2.

1S2 2S2 2P5 is the electrical configuration of the nitrogen atom.

The electrical configuration of oxygen is 1S2 2S2 2P6.

When you look at the electrical configuration of the elements, you’ll notice that hydrogen has only one electron, nitrogen has five, and oxygen has six in the outermost shell.

It will aid our understanding of how these elements create bonds by sharing electrons.

Let’s have a look at the procedures to deciphering HNO3’s Lewis structure.

Step 1: Determine the number of electrons in the outer shell of the atoms.

Nitrogen has five valence electrons while hydrogen has only one. There are 18 valence electrons in each of the three oxygen atoms.

The total number of electrons in the outermost shell is thus 1+5+18 = 24.

Step 2: Determine the number of electrons required for Octet.

The hydrogen atom requires two electrons, the nitrogen atom requires eight electrons, and oxygen requires 24 electrons.

So, for an octet, the total number of electrons required is 2+8+3*8 = 34.

Step three is to figure out how many bonding electrons there are.

By subtracting the amount of electrons in an outermost shell from the number of electrons required for an octet, we may find it.

It’s 34-24 = 10 in this case.

Step 4: We must now determine the number of bonds in the molecule.

As a result, 10/2 = 5

Step 5: We need to figure out how many lone pairs there are (electrons not forming a bond).

We can acquire it by subtracting the valence electrons from the electrons involved in bond formation. Here, 24-10 = 14, which equals 7 lone pairs.

To draw the Lewis structure of HNO3, we must first identify the centre atom, which in this chemical is nitrogen, which has the lowest electronegativity.

The following step is to arrange the remaining atoms, followed by drawing the bond pairs and lone pairs.

Because every atom in HNO3 follows the octet’s rule, the core N atom is placed first in the Lewis structure. Then, on three sides, we place two O atoms and one OH ion.

To follow Octet’s rule, one oxygen atom and the OH ion are joined by single bonds, while the remaining oxygen atom is attached to nitrogen by a double bond.

The nitrogen atom achieves a stable configuration of eight electrons in this fashion. With two oxygen atoms, it creates a double and a single bond, and with an OH ion, it forms a single bond.

Only oxygen is surrounded by lone pairs here. Two lone pairs are formed by the oxygen atom creating a double bond, whereas one bond pair and three lone pairs are formed by the other oxygen atom.

The oxygen atom in the OH ion possesses two lone pairs, one single bond with hydrogen, and one single bond with nitrogen.

Nitric Acid’s Molecular Geometry (HNO3)

When we look at the form of the HNO3 molecule, we can see that it is trigonal planar.

The Lewis structure and the VSEPR (valence shell electron pair repulsion) theory dictate the molecular geometry of each molecule.

The Lewis molecular structure of HNO3 shows that H has one valence electron, N has five, and the O atom has six.

The nitrogen atom forms a single connection with one oxygen atom during the bonding process. With another oxygen atom and the OH ion, it creates two single bonds.

The oxygen atoms form lone pairs, with the first having two and the second having three. The OH ion’s oxygen atom has two lone pairs.

According to the VSEPR theory, when electrons or bonds repel each other, they tend to stay at the maximum distance. It maintains the form of the molecules.

Apart from that, the structure of a molecule is determined by covalent bonds and lone pairs.

The electron pairs in a bond repel each other, with the most repulsive force between two lone pairs. The difference between a lone pair and a bond pair is smaller, and the difference between bond pairs is the smallest.

The VSEPR theory can help us comprehend the molecular geometry of HNO3. Nitrogen is the core atom.

Because the electron pairs repel each other with maximal force, the atoms around them maintain the greatest distance possible, minimising the repulsion force.

The steric number is another factor that aids in determining the molecule structure (SN). The number can be calculated by multiplying the lone pairs with the atoms that are involved in bonds.

There is no lone pair on nitrogen in HNO3. It forms bonds with three oxygen atoms. As a result, the nitrogen atom in HNO3 has an SN of three.

The oxygen atom linked to hydrogen, on the other hand, has an SN of 4 due to two bond pairs and two lone pairs.

The compounds with the central atom having (Stearic Number) SN 3 and the lone pair having a shape of trigonal planar can be found in the VSEPR geometry table.

The polarity of the HNO3 molecule is owing to its lone pair and asymmetrical structure.

The HNO3 Molecule Has Been Hybridized

Before we can grasp HNO3 hybridization, we must first understand what hybridization is.

Hybridization is the process of mixing two orbitals with the same energy level to create a new type of orbitals.

To grasp the shape of a molecule, you must first understand how atoms are grouped in a molecule.

We can learn about a chemical substance’s physical and chemical properties, as well as its shape, if we can visualise its structure.

The molecule HNO3 is generated through the hybridization of two orbitals in the Lewis structure. The steric number of nitrogen is 3, while the steric number of the oxygen atom in the OH ion is 4.

HNO3 features SP2 hybridization on the N atom and SP3 hybridization on the O atom.

So, nitric acid possesses 13 (3 + 4 + 2*3) hybrid orbitals before bonding, but only six hybrid orbitals after bonding.

HNO3 molecular orbital diagram

The 2sp2 orbital of nitrogen and a hybrid orbital atom from O atoms produce the sigma bonds between N and O atoms.

Three sigma bonding and antibonding orbitals are produced as a result.

The 1s orbital of hydrogen and 2sp3 orbitals of oxygen are used in the single sigma bond between hydrogen and oxygen. It produces a sigma bonding and antibonding orbital as a consequence.

Three pi orbitals are formed by nitrogen and two oxygen atoms. The 2sp2 orbitals on oxygen that are left behind do not participate in bonding.


The Lewis structure, molecular geometry, and hybridization of HNO3 are all essential in chemistry; they help us learn a lot about this vital molecule.

We’ve focused on learning the structure of this molecule in this essay. Knowing these facts will aid us in better comprehending the form and properties of this molecule. We hope you found it helpful.

Read more: Molecular Geometry, Hybridization, and Polarity of CH3OCH3 Lewis Structure

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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