HI Molecular Geometry - Science Education and Tutorials

Q: What is the molecular notation for HI molecule?

HI molecular notation is AX1N3.

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

Table of Contents

Key Points To Consider When drawing The HI Molecular Geometry

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

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

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

Overview: HI electron and molecular geometry

According to the VSEPR theory, the HI molecule ion possesses linear or tetrahedral molecular geometry. Because the center atom, iodine, has one H-I single bond with the one hydrogen atom surrounding it. The H-I bond angle is 180 degrees in the tetrahedral HI molecular geometry. The HI 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-I single bond at the HI molecular geometry. After linking the one hydrogen atom and three lone pairs of electrons on the iodine atom in the tetrahedral form, it maintains the tetrahedral-shaped structure. In the HI molecular geometry, the H-I single bond has stayed in the one terminal and three lone pairs of electrons on the iodine atom of the tetrahedral molecule.

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

How to find HI hybridization and molecular geometry

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

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

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

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

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

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

The lone pair of electrons in the iodine atom of the HI molecule is three.

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

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

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

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

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

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

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

But in the central, iodine 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 HI molecule

What is HI 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

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

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

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

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

No. Hyb of HI= 3+1=4

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

Molecular Geometry Notation for HI Molecule :

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

The AXN notation of HI molecule is as follows:
The central iodine atom in the HI molecule is denoted by the letter A.
The bound pairs (one H-I bond) 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 HI molecular geometry

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

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

Summary:

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