Molecular Geometry, Hybridization, and Polarity of NOCl Lewis Structure

Do you know what the term ‘aqua regia’ means? I’m sure you have if you’re a chemistry student. The mixture of nitric acid and hydrochloric acid has a 1:3 molar ratio.

In today’s article, we’ll discuss one of the components of aqua regia: Nitrosyl Chloride (NOCl).

NOCl is a reddish red gas with a density of 2.872 mg/ml and a molar mass of 65.46 g/mol. It possesses significant oxidising characteristics as well as being an electrophile. It has a high water reactivity.

It can be made in the lab by dehydrating HNO2 or nitrous acid in a reversible manner. The following is the reaction:

HNO2   +    HCl    —–>    H2O   +   NOCl

Caprolactam ((CH2)5C(O)NH) is produced industrially using nitrosyl chloride. It is a very poisonous gas that also hastens the combustion of flammable items.

Chemical Adhesion

It’s crucial to understand the science behind a molecule’s or chemical composition’s development when studying it.

Atoms from various elements combine to form molecular structures, which then combine to form chemical compounds. As a result, this study of atomic attraction that leads to novel products is a fascinating and important chapter in chemistry.

A chemical bond is the attractive force that holds atoms together.

As a result, the nature of NOCl’s chemical bonding will be discussed in this article. To accomplish so, we’ll first go over the Lewis Structure notion.

Structure of Lewis

Do you understand what valence shell electrons are? They are the electrons found in the outermost shell of an element’s atom.

We can generate a simplified representation of chemical bonding if we depict these electrons as dot notations encircling the respective atoms inside a molecule and mark out the type of bond created between them. This is referred to as the Lewis Structure.

The 2D diagrammatical representation of the distribution of electrons around atomic atoms in a molecule is known as the Lewis Structure. The electron-dot structure is another name for it.

NOCl’s Lewis Structure

Take a molecule of NOCl as the first step. One atom of nitrogen, one atom of chlorine, and one atom of oxygen make up a nitrosyl chloride molecule.

Step 2: We’ll now determine the total number of valence electrons in a single NOCl molecule. Take a look at the periodic table to do so.

Nitrogen is a member of group 15 and has an atomic number of 7. It has 5 electrons in its valence shell.

Oxygen is a member of group 16 and has an atomic number of 8. It has 6 electrons in its valence shell.

Chlorine is a member of Group 17 and has an atomic number of 17. It has a valence electron count of seven.

In the NOCl molecule, the total number of valence electrons is 5 + 6 + 7 = 18.

Step 3: We’ll now determine the molecule’s core atom. With a few exceptions, the element with the lowest electronegativity value obtains the centre position as a general rule.

Nitrogen is the core atom in this structure.

Step 4: We’ll design a diagram in which the valence electrons are represented by dot notations, and we’ll figure out how bonds arise.

Step 5: The octet rule is used here.

The octet rule asserts that the major group elements of the periodic table have a tendency to achieve the noble gas elements’ octet valence shell configuration. As can be seen in the diagram above, Oxygen and Chlorine have attained octet configuration, whereas Nitrogen is two electrons short.

To establish a double bond, move two electrons from oxygen to nitrogen.

Note that a single bond is formed when two electrons are shared, a double bond is formed when four electrons are shared, and so on.

In the diagram above, all three atoms have now reached octet configurations.

Step 6: We have no way of knowing if the diagram we drew is the correct Lewis Structure diagram. To do so, we must examine the formal charge values.

N has a formal charge of 5 – 0.5*6 – 2 = 5 – 3 – 2 = 0 in NOCl.

O’s formal charge is 6 – 0.5*4 – 4 = 6 – 2 – 4 = zero.

Cl has a formal charge of 7 – 0.5*2 – 6 = 7 – 1 – 6 = zero.

We may reasonably infer that we have our requisite Lewis Structure diagram for Nitrosyl Chloride because all of the atomic elements are present in their lowest feasible formal charge values.

Between N and O, there is a double bond, while between N and Cl, there is a single bond.

Molecular Geometry of NOCl

The 2-dimensional graphical representation of NOCl was discovered in the preceding section. The Lewis Structure notion, on the other hand, has its own set of limitations:

It is unable to anticipate the molecular geometry of any given molecule structure in three dimensions.

It doesn’t go into great depth regarding chemical bonds or offer us a clear picture of how atoms are arranged in space.

We’ll use the Valence Shell Electron Pair Repulsion (VSEPR) theory to help us here.

We already understand how valence electrons form bound and lone pairs surrounding atoms within a molecule. Around the atomic nuclei, negatively charged electrons create a thick cloud.

Electrons have a tendency to repel each other, according to the VSEPR model, because they are similar charges. To counteract this repulsive tendency, the atoms move further apart and attempt to maintain the molecule structure.

The molecular geometry of NOCl will be explained using the VSEPR model.

Nitrogen is the core atom in NOCl.

We can utilise AXnEx notations to find out the 3D molecular structures according to VSEPR theory.

Here, A represents the core atom, X represents the surrounding atoms, and E represents the lone pair of electrons encircling the central atom.

We have one O and one Cl around Nitrogen, ‘n’ = 2, and two lone electrons, i.e. one lone pair, around the core atom, ‘x’ = 1.

AX2E1 is the required VSEPR notation for nitrosyl chloride.

The VSEPR chart is depicted in the image below:

NOCl has a bent molecular structure, as shown in the diagram.

The O=N and Cl-N bonds stretch to form a linear structure when we look at the molecule. The lone pair on top of central Nitrogen, on the other hand, pushes the other atoms down, resulting in a lower bond angle and bent molecular geometry.

Around 113 degrees is the bond angle.

Hybridization of NOCl

You will almost certainly come across the phrase “hybridization” if you are investigating a molecule’s chemical bonds.

One of the most notable notions to describe the nature of bonding is orbital hybridization. Hybridized orbitals are formed when the atomic orbitals of the same atomic element merge and fuse.

For example, in an ethylene molecule, one s and two p orbitals of a carbon atom combine to generate three sp2 hybrid orbitals that participate in creating single bonds with hydrogen and the other carbon atom.

In order to understand the sort of hybridization in NOCl, we must first define a key term: Steric Number.

The sum of the number of sigma bonds around the atom and the number of lone pairs of electrons on the atom is known as the steric number.

A sigma bond is found in a single bond, while a sigma bond and a pi bond are found in a double bond.

Number of atoms bound to the core atom inside a molecule + Number of lone pairs of electrons attached to the central atom = Steric number

Nitrogen steric number in NOCl = 2 + 1 = 3.

This indicates that sp2 has been hybridised.

As a result, we can say that nitrosyl chloride’s core atom is sp2 hybridised.

Polarity of NOCl

Chemistry’s topic of polarity is fascinating. Another relevant term is electronegativity, which is closely related to this attribute.

The tendency of an atom to gain negatively charged electrons is known as electronegativity.

Polarity is defined as the separation of electric charges resulting in a net dipole moment and is connected to the distribution of charges inside a compound.

When the electronegativity difference between the atoms at both ends is significant, the bond is polar (usually more than 0.4-0.5). When there is asymmetry in a molecule, that is, when the molecule does not have a linear or symmetrical geometry, the dipoles do not balance out, and we end up with a polar molecule.

Let’s see whether NOCl is polar or non-polar now:

N has an electronegativity of 3.04, O has a value of 3.44, and Cl has a value of 3.16.

Because the O and Cl ends are extremely electrophilic, electrons are drawn to them. The lone pair also bends the geometry of NOCl. A polar molecule is defined by its asymmetry and unequal charge distribution.

You should also check out the article I wrote about NOCl polarity.


The Lewis Structure, VSEPR theory to forecast molecular geometry, orbital hybridization, and polarity of the NOCl molecule were all explored in depth in this article.

Good luck with your studies!

Read more: Geometry, Hybridization, and Polarity of CH3OH 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.


Please enter your comment!
Please enter your name here

Read More