IBr3 Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for IBr3 molecule?

IBr3 molecular notation is AX3N2.

Tribromo iodine or iodine tribromide(IBr3) has the composition of one iodine and three bromine atoms. What is the molecular geometry of iodine tribromide?. Drawing and predicting the IBr3 molecular geometry is very easy by following the given method. Here in this post, we described step by step to construct IBr3 molecular geometry. Iodine and bromine come from the 17th family group in the periodic table. Iodine or bromine has seven valence electrons.

Table of Contents

Key Points To Consider When drawing The IBr3 Molecular Geometry

A three-step approach for drawing the IBr3 molecular can be used. The first step is to sketch the molecular geometry of the IBr3 molecule, to calculate the lone pairs of the electron in the central iodine atom; the second step is to calculate the IBr3 hybridization, and the third step is to give perfect notation for the IBr3 molecular geometry.

The IBr3 molecular geometry is a diagram that illustrates the number of valence electrons and bond electron pairs in the IBr3 molecule in a specific geometric manner. The geometry of the IBr3 molecule 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 IBr3 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 three I-Br bonds (dipole moment properties of the IBr3 molecular geometry). The iodine-bromine and three iodine-bromine bonds in the iodine tribromide(IBr3), for example, are polarised toward the more electronegative value bromine atoms, and because all three (I-Br) bonds have the same size and polarity, their sum is nonzero due to the IBr3 molecule’s bond dipole moment due to pulling the electron cloud to the downside in the trigonal bipyramidal geometry, and the IBr3 molecule is classified as a polar molecule.

The molecule of iodine tribromide(with trigonal bipyramidal shape IBr3 molecular geometry) is tilted at slightly smaller than 90 degrees bond angle of Br-I-Br. It has a difference in electronegativity values between iodine and bromine atoms, with bromine’s pull the electron cloud being greater than iodine’s. But bond polarity of I-Br is not canceled to each other in the trigonal bipyramidal geometry. As a result, it has a permanent dipole moment in its molecular structure. The IBr3 molecule has a dipole moment due to an unequal charge distribution of negative and positive charges.

Overview: IBr3 electron and molecular geometry

According to the VSEPR theory, the IBr3 molecule possesses trigonal bipyramidal molecular geometry. Because the center atom, iodine, has three I-Br bonds with the three bromine atoms surrounding it. The Cl-I-Br bond angle is slightly smaller than 90 degrees in the trigonal bipyramidal IBr3 molecular geometry. The IBr3 molecule has a trigonal geometry shape because it contains three bromine atoms.

There are three I-Br bonds at the IBr3 molecular geometry. After linking the three bromine atoms and two lone pairs of electrons in the trigonal bipyramidal form, it maintains the distorted T-shaped structure. In the IBr3 molecular geometry, the I-Br bonds have stayed in the three terminals and two lone pairs of electrons on the iodine atom of the trigonal bipyramidal molecule.

The center iodine atom of IBr3 has two lone pairs of electrons, resulting in trigonal bipyramidal IBr3 electron geometry. However, the molecular geometry of IBr3 looks distorted T-shaped and two lone pairs of electrons on the iodine of the IBr3 geometry. It’s the IBr3 molecule’s symmetrical geometry. As a result, the IBr3 molecule is polar.

How to find IBr3 hybridization and molecular geometry

Calculating lone pairs of electrons on iodine in the IBr3 geometry:

1.Determine the number of lone pairs of electrons in the core iodine atom of the IBr3 Lewis structure. Because the lone pairs of electrons on the iodine atom are mostly responsible for the IBr3 molecule geometry distortion, we need to calculate out how many there are on the central iodine atom of the IBr3 Lewis structure.

Use the formula below to find the lone pair on the iodine atom of the IBr3 molecule.
L.P(I) = V.E(I) – N.A(I-Br)/2

Lone pair on the central iodine atom = L.P(I)
The core central iodine atom’s valence electron = V.E(I)
Number of I-Br bonds = N.A (I-Br)
calculation for iodine atom lone pair in IBr3 molecule.

For instance of IBr3, the central atom, iodine, has seven electrons in its outermost valence shell, three I-Br bond connections. This gives a total of three connections.

As a result of this, L.P(I) = (7 –3)/2=2

The lone pairs of electrons in the iodine atom of the IBr3 molecule are two.

Calculating lone pairs of electrons on bromine in the IBr3 geometry:

Use the formula below to find the lone pair on the bromine atom of the IBr3 molecule.
L.P(F) = V.E(F) – N.A(I-Br)

Lone pair on the terminal bromine atom = L.P(F)
Terminal bromine atom’s valence electron = V.E(F)
Number of I-Br bonds = N.A ( I-Br)
calculation for bromine atom lone pair in IBr3 molecule.

For instance of IBr3, three terminal atoms, bromine, have seven electrons in its outermost valence shell, one I-Br bond connection. This gives a total of three I-Br bond connections. But we are considering only one connection for the calculation.

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

The lone pairs of electrons in the bromine atom of the IBr3 molecule are six. Three bromine atoms are connected with the central iodine atom.

In the IBr3 electron geometry structure, the lone pair on the central iodine atom is two. lone pairs of electrons in the bromine atom have six. Three bromine atoms have 18 lone pairs of electrons.

It means there are two lone pairs of electrons in the core iodine atom. Two lone pair of electrons on the central iodine atom is responsible for the trigonal bipyramidal nature of IBr3 molecular geometry. But in the structure bromine atoms are polarised sidewise in their geometry.

The two lone pairs of electrons are placed at another side of the IBr3 geometry. Because the iodine atom is a lower electronegative value as compared with other atoms in the IBr3 molecule. Three bromine atoms are polarized towards the sidewise in the IBr3 structure.

But in reality, the IBr3 has two lone pairs of electrons in its structure. This makes the IBr3 more irregular structure of the molecule. Because there is electric repulsion between bond pairs and lone pairs. But some sort of interaction is there between bromine lone pairs and bond pairs. But it is negligible.

Calculate the number of molecular hybridizations of the IBr3 molecule

What is IBr3 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

IBr3 molecule is made of one iodine, three bromine atoms. The bromine and iodine atoms have s and p orbitals. Bromine comes as the third element from the halogen family in the periodic table. The iodine atom also belongs to the same family group. But it falls as the fourth element in the periodic table.

When these atoms combine to form the IBr3 molecule, its atomic orbitals mix and form unique molecular orbitals due to hybridization.

How do you find the IBr3 molecule’s hybridization? We must now determine the molecular hybridization number of IBr3.

The formula of IBr3 molecular hybridization is as follows:
No. Hyb of IBr3= N.A(I-Br bonds) + L.P(I)
No. Hy of IBr3= the number of hybridizations of IBr3
Number of I-Br bonds = N.A (I-Br bonds)
Lone pair on the central iodine atom = L.P(I)
Calculation for hybridization number for IBr3 molecule

In the IBr3 molecule, iodine is a core central atom with three bromine atoms connected to it. It has two lone pairs of electrons on iodine. The number of IBr3 hybridizations (No. Hyb of IBr3) can then be estimated using the formula below.

No. Hyb of IBr3= 3+2 =5

The IBr3 molecule hybridization is five. The iodine and bromine atoms have s and p orbitals. The sp3d hybridization of the IBr3 molecule is formed when one S orbital, three p orbitals, and one d orbital join together to form the IBr3 molecular orbital.

Molecular Geometry Notation for IBr3 Molecule :

Determine the form of IBr3 molecular geometry using VSEPR theory. The AXN technique is commonly used when the VSEPR theory is used to calculate the shape of the IBr3 molecule.

The AXN notation of IBr3 molecule is as follows:
The central iodine atom in the IBr3 molecule is denoted by the letter A.
The bound pairs (three I-Br bonds) of electrons to the core iodine atom are represented by X.
The lone pairs of electrons on the central iodine atom are denoted by the letter N.
Notation for IBr3 molecular geometry

We know that iodine is the core atom, with three electron pairs bound (three I-Br) and two lone pairs of electrons. The general molecular geometry formula for IBr3 is AX3N2.

According to the VSEPR theory, if the IBr3 molecule has an AX3N2 generic formula, the molecular geometry and electron geometry will both trigonal bipyramidal forms.

Name of Molecule	Iodine tribromide
Chemical molecular formula	IBr3
Molecular geometry of IBr3	Trigonal bipyramidal
Electron geometry of IBr3	Trigonal bipyramidal
Hybridization of IBr3	sp3d
Bond angle (Br-I-Br)	slightly smaller than 90 degree
Total Valence electron for IBr3	28
The formal charge of IBr3 on iodine	0

Summary:

In this post, we discussed the method to construct IBr3 molecular geometry, the method to find the lone pairs of electrons in the central iodine atom, IBr3 hybridization, and IBr3 molecular notation. Need to remember that, if you follow the above-said method, you can construct the IBr3 molecular structure very easily.