HBr Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for HBr molecule?

HBr molecular notation is AX1N3.

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

Table of Contents

Key Points To Consider When drawing The HBr Molecular Geometry

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

The HBr molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the HBr molecule in a specific geometric manner. The geometry of the HBr 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 HBr 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-Br single bonds (dipole moment properties of the HBr molecular geometry). One hydrogen-bromine single bonds in the hydrogen bromide(HBr), for example, are polarised toward the more electronegative value bromine atom, and because (H-Br) single bonds have the same size and polarity, their sum is nonzero due to the HBr molecule’s bond dipole moment due to pulling the electron cloud to the two side of linear or tetrahedral geometry, and the HBr molecule is classified as a polar molecule.

The molecule of hydrogen bromide(with tetrahedral shape HBr molecular geometry) is tilted at 180 degrees bond angle of H-Br. It has a difference in electronegativity values between bromine and hydrogen atoms, with bromine’s pull the electron cloud being greater than hydrogen’s. But bond polarity of H-Br 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 HBr molecule has a nonzero dipole moment due to an unequal charge distribution of negative and positive charges in the linear or tetrahedral geometry.

Overview: HBr electron and molecular geometry

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

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

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

How to find HBr hybridization and molecular geometry

Calculating lone pairs of electrons on bromine in the HBr geometry:

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

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

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

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

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

The lone pair of electrons in the bromine atom of the HBr molecule is three.

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

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

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

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

For instance of HBr, their terminal atoms, hydrogen, have one electron in its outermost valence shell, one H-Br single bond connection. This gives a total of one H-Br 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 HBr molecule is zero. One hydrogen atom is connected with the central bromine atom.

In the HBr electron geometry structure, the lone pairs on the central bromine 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 bromine atom. Three lone pair of electrons on the central bromine atom is responsible for the linear or tetrahedral nature of HBr 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 HBr geometry. Because the hydrogen atom is a lower electronegative value as compared with other atoms in the HBr molecule. One hydrogen atom is polarized towards the sidewise in the HBr structure.

But in reality, the HBr has three lone pairs of electrons in its structure. This makes the HBr 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 bromine of another HBr molecule. Here, hydrogen of one molecule acts as an acceptor and bromine of another molecule as a donor. This is called hydrogen bonding between the two HBr molecules. This is one of the main intermolecular forces in HBr.

But in the central, bromine 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 HBr molecule

What is HBr 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

HBr molecule is made of one bromine and hydrogen atom. The hydrogen and bromine 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 bromine 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 HBr molecule, its atomic orbitals are mixed and form unique molecular orbitals due to hybridization.

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

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

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

No. Hyb of HBr= 3+1=4

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

Molecular Geometry Notation for HBr Molecule :

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

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

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

According to the VSEPR theory, if the HBr 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 bromide
Chemical molecular formula	HBr
Molecular geometry of HBr	Tetrahedral or linear
Electron geometry of HBr	Tetrahedral or linear
Hybridization of HBr	sp3
Bond angle (H-Br)	180º degree
Total Valence electron for HBr	8
The formal charge of HBr on bromine	0

Summary:

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