HCl Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for HCl molecule?

HCl molecular notation is AX1N3.

Hydrogen chloride or hydrochloric acid(HCl) has the composition of one chlorine and one hydrogen atom. What is the molecular geometry of hydrogen chloride?. Drawing and predicting the HCl molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct HCl molecular geometry. Chlorine and hydrogen come from the 17th and 1st family groups in the periodic table. Chlorine and hydrogen have seven and one valence electrons respectively.

Table of Contents

Key Points To Consider When drawing The HCl Molecular Geometry

A three-step approach for drawing the HCl molecular can be used. The first step is to sketch the molecular geometry of the HCl molecule, to calculate the lone pairs of the electron in the central chlorine atom; the second step is to calculate the HCl hybridization, and the third step is to give perfect notation for the HCl molecular geometry.

The HCl molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the HCl molecule in a specific geometric manner. The geometry of the HCl molecule ion can then be predicted using the Valence Shell Electron Pair Repulsion Theory (VSEPR Theory) and molecular hybridization theory, which states that molecules will choose the HCl geometrical shape in which the electrons have from one another in the specific molecular structure.

Finally, you must add their bond polarities characteristics to compute the strength of the one H-Cl single bonds (dipole moment properties of the HCl molecular geometry). One hydrogen-chlorine single bonds in the hydrogen chloride(HCl), for example, are polarised toward the more electronegative value chlorine atom, and because (H-Cl) single bonds have the same size and polarity, their sum is nonzero due to the HCl molecule’s bond dipole moment due to pulling the electron cloud to the two side of linear or tetrahedral geometry, and the HCl molecule is classified as a polar molecule.

The molecule of hydrogen chloride(with tetrahedral shape HCl molecular geometry) is tilted at 180 degrees bond angle of H-Cl. It has a difference in electronegativity values between chlorine and hydrogen atoms, with chlorine’s pull the electron cloud being greater than hydrogen’s. But bond polarity of H-Cl is not canceled to each other in the linear or tetrahedral geometry. As a result, it has a nonzero permanent dipole moment in its molecular structure. The HCl molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges in the linear or tetrahedral geometry.

Overview: HCl electron and molecular geometry

According to the VSEPR theory, the HCl molecule ion possesses linear or tetrahedral molecular geometry. Because the center atom, chlorine, has one H-Cl single bond with the one hydrogen atom surrounding it. The H-Cl bond angle is 180 degrees in the tetrahedral HCl molecular geometry. The HCl molecule has a linear or tetrahedral geometry shape because it contains one hydrogen atom in the tetrahedral and three corners with three lone pairs of electrons.

There is one H-Cl single bond at the HCl molecular geometry. After linking the one hydrogen atom and three lone pairs of electrons on the chlorine atom in the tetrahedral form, it maintains the tetrahedral-shaped structure. In the HCl molecular geometry, the H-Cl single bond has stayed in the one terminal and three lone pairs of electrons on the chlorine atom of the tetrahedral molecule.

The center chlorine atom of HCl has three lone pairs of electrons, resulting in tetrahedral HCl electron geometry. However, the molecular geometry of HCl looks tetrahedral or linear-shaped and has three lone pairs of electrons on the chlorine of the HCl geometry. It’s the HCl molecule’s slight asymmetrical geometry. As a result, the HCl molecule is polar.

How to find HCl hybridization and molecular geometry

Calculating lone pairs of electrons on chlorine in the HCl geometry:

1.Determine the number of lone pairs of electrons in the core chlorine atom of the HCl Lewis structure. Because the lone pairs of electrons on the chlorine atom are mostly responsible for the HCl molecule geometry planar, we need to calculate out how many there are on the central chlorine atom of the HCl Lewis structure.

Use the formula below to find the lone pair on the chlorine atom of the HCl molecule.
L.P(Cl) = V.E(Cl) – N.A(H-Cl)

Lone pair on the central chlorine atom in HCl = L.P(Cl)
The core central chlorine atom’s valence electron in HCl = V.E(Cl)
Number of H-Cl bond = N.A (H-Cl)
calculation for chlorine atom lone pair in HCl molecule.

For instance of HCl, the central atom, chlorine, has seven electrons in its outermost valence shell, one H-Cl single bond connection. This gives a total of one connection.

As a result of this, L.P(Cl) = (7 –1)=6

The lone pair of electrons in the chlorine atom of the HCl molecule is three.

Calculating lone pair of electrons on hydrogen in the HCl geometry:

Finding lone pair of electrons for the terminal hydrogen atom is similar to the central chlorine atom. We use the following formula as given below

Use the formula below to find the lone pair on the hydrogen atom of the HCl molecule.
L.P(H) = V.E(H) – N.A(H-Cl)

Lone pair on the terminal hydrogen atom in HCl = L.P(H)
Terminal hydrogen atom’s valence electron in HCl= V.E(H)
Number of H-Cl bonds = N.A ( H-Cl)
calculation for hydrogen atom lone pair in HCl molecule.

For instance of HCl, their terminal atoms, hydrogen, have one electron in its outermost valence shell, one H-Cl single bond connection. This gives a total of one H-Cl single bond connection. But we are considering only one connection for the calculation.

As a result of this, L.P(H) = (1 –1)=0

The lone pair of electrons in the hydrogen atom of the HCl molecule is zero. One hydrogen atom is connected with the central chlorine atom.

In the HCl electron geometry structure, the lone pairs on the central chlorine atom are three, lone pairs of electrons in the hydrogen atom have zero. One hydrogen atom has no lone pairs of electrons.

It means there are three lone pairs of electrons in the core chlorine atom. Three lone pair of electrons on the central chlorine atom is responsible for the linear or tetrahedral nature of HCl molecular geometry. But in the structure hydrogen atom is polarised sidewise in their linear or tetrahedral geometry.

The three lone pairs of electrons are placed at another side of the HCl geometry. Because the hydrogen atom is a lower electronegative value as compared with other atoms in the HCl molecule. One hydrogen atom is polarized towards the sidewise in the HCl structure.

But in reality, the HCl has three lone pairs of electrons in its structure. This makes the HCl more asymmetrical in the structure of the molecule. Because there is electric repulsion between bond pairs and lone pairs.

But some sort of interaction is there between hydrogen empty hole and lone pairs of electrons of chlorine of another HCl molecule. Here, hydrogen of one molecule acts as an acceptor and chlorine of another molecule as a donor. This is called hydrogen bonding between the two HCl molecules. This is one of the main intermolecular forces in HCl.

But in the central, chlorine atom has three lone pairs of electrons and these lone pair electrons are placed in the three corners of the tetrahedral.

Calculate the number of molecular hybridizations of the HCl molecule

What is HCl hybridization? This is a very fundamental question in the field of molecular chemistry. All the molecules are made of atoms. In chemistry, atoms are the fundamental particles. There are four different types of orbitals in chemistry. They are named s, p, d, and f orbitals.

The entire periodic table arrangement is based on these orbital theories. Atoms in the periodic table are classified as follows:

s- block elements
p- block elements
d-block elements
f-block elements
Atoms are classified in the periodic table

HCl molecule is made of one chlorine and the hydrogen atom. The hydrogen and chlorine atoms have s and p orbitals. But hydrogen atom has only s orbital in the ground state. Hydrogen comes as the first element in the periodic table. The chlorine atom also belongs to the halogen family group. But it falls as the third element in the periodic table.

When these atoms combine to form the HCl molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

How do you find the HCl molecule’s hybridization? We must now determine the molecular hybridization number of HCl.

The formula of HCl molecular hybridization is as follows:
No. Hyb of HCl= N.A(H-Cl bond) + L.P(Cl)
No. Hy of HCl = the number of hybridizations of HCl
Number of H-Cl bonds = N.A (H-Clbonds)
Lone pair on the central chlorine atom = L.P(Cl)
Calculation for hybridization number for HCl molecule

In the HCl molecule, chlorine is a core central atom with one hydrogen atom connected to it. It has three lone pairs of electrons on chlorine. The number of HCl hybridizations (No. Hyb of HCl) can then be estimated using the formula below.

No. Hyb of HCl= 3+1=4

The HCl molecule ion hybridization is four. The chlorine and hydrogen atoms have s and p orbitals. The sp3 hybridization of the HCl molecule is formed when one s orbital and three p orbitals join together to form the HCl molecular orbital.

Molecular Geometry Notation for HCl Molecule :

Determine the form of HCl molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the HCl molecule.

The AXN notation of HCl molecule is as follows:
The central chlorine atom in the HCl molecule is denoted by the letter A.
The bound pairs (one H-Cl bond) of electrons to the core chlorine atom are represented by X.
The lone pairs of electrons on the central chlorine atom are denoted by the letter N.
Notation for HCl molecular geometry

We know that HCl is the core atom, with one electron pair bound (one H-Cl) and three lone pairs of electrons. The general molecular geometry formula for HCl is AX1N3.

According to the VSEPR theory, if the HCl molecule ion has an AX1N3 generic formula, the molecular geometry and electron geometry will both be tetrahedral or linear-shaped forms.

Name of Molecule	Hydrogen chloride
Chemical molecular formula	HCl
Molecular geometry of HCl	Tetrahedral or linear
Electron geometry of HCl	Tetrahedral or linear
Hybridization of HCl	sp3
Bond angle (H-Cl)	180º degree
Total Valence electron for HCl	8
The formal charge of HCl on chlorine	0

Summary:

In this post, we discussed the method to construct HCl molecular geometry, the method to find the lone pairs of electrons in the central HCl atom, HCl hybridization, and HCl molecular notation. Need to remember that, if you follow the above-said method, you can construct the HCl molecular structure very easily.