Chemical Hybridization and Polarity of the ICl3 Lewis Structure

An Interhalogen molecule known as ICl3 (Iodine Trichloride) is ICl3. molecules with at least two separate halogen atoms make up the term “interhalogen compounds”.

ABn, where n is 1, 3, 5, or 7; A and B are the less and more electronegative elements, respectively, in these compounds. Because of this, they are more reactive than the individual Halogen atoms from which they are generated,

When exposed to light, ICl3 is a bright yellow solid that turns red due to the production of elemental iodine. Solid-state I2Cl6 occurs in the form of a dimer. It has a melting point of 63 degrees Celsius. Iodine trichloride has a molecular mass of 233.26 g/mol.

Let’s begin our investigation into the chemistry of iodine trichloride by examining its chemical bonds.

In order to understand Lewis theory’s Lewis structure, we will first look at the iodine atom’s hybridization in the iodine trichloride molecule.

After that, we’ll look at its polarity — whether it’s polar or nonpolar.

Structure of ICl3

Drawing a Lewis structure is the finest way to show the two-dimensional structure of any compound. Only electrons in the valence (outermost) shell of an atom are included in this list.

Helium and Hydrogen, according to the lewis theory, prefer to have eight electrons surrounding them in the valence shell.

The sketching of a compound’s Lewis structure follows these steps:

Counting the valence electrons in solution

An illustration of the skeletal system

To complete the Lewis structure by meeting the octet rule for every single element, if at all possible.

I and Cl have a [Kr] 4d105s25p5 and [Ne] 3s23p5 electrical arrangement, respectively. Both atoms contain seven valence electrons, thus they have seven total. [7 X 1) + (7 X 3)] = 28 electrons, which is the total amount of valence electrons

Iodine will be the core atom in the ICl3 skeleton, with all three chlorine atoms surrounding it.

Since the iodine-trichloride Lewis structure is:

Chlorine atoms are surrounded by eight electrons, but iodine, the core element, is surrounded by ten electrons, as can be shown.

For example, the elements in the third or fourth period of the periodic table have 3d electrons for bonding, which is one of the octet rule exceptions.

Because of this, certain elements can have more than eight electrons surrounding them.

A single bond is represented by a single pair of electrons that are both in the same orbital. Because of this, the iodine trichloride Lewis structure is represented by the following formula:

The Lewis structure of iodine trichloride does not allow us to determine its shape or molecular geometry. This is well explained by the idea of valence shell electron pair repulsion (VSEPR).

Iodine trichloride’s shape can be predicted by looking at VSEPR theory.

Chemistry of ICl3 Molecules

The form and molecular geometry of a molecule are determined by the number of bonded (bond pair) and non-bonded (lone pair) valence shell electrons, according to VSEPR theory.

Three bond pairs and two single electron pairs can be seen in the Lewis structure of Iodine.

Iodine trichloride’s molecular geometry will deviate from its actual shape because of this. Using the following table, one can determine the molecule’s molecular geometry and shape:

General formulaNumber of
bond pairs (B)
Number of
lone pairs (E)
Molecular geometryShape
AX330Trigonal planarTrigonal planar
AX2E21Trigonal planarBent
AX550Trigonal bipyramidalTrigonal
AX4E41Trigonal bipyramidalSea Saw
AX3E232Trigonal bipyramidalT-shape
AX4E242OctahedralSquare planar

Iodine has three bond pairs and two lone pairs of electrons on it, making it similar to AX3E3, according to the table.

Iodine trichloride’s trigonal bipyramidal geometry and T-shaped shape can be depicted in this way:

You may wonder why both electron lone pairs are in an equatorial position rather than an axial one.

Because the electron is negatively charged, the pair of electrons will resist each other in accordance with the VSEPR theory. As a result, electron pairs will occupy the available area in order to reduce repulsion and increase distance.

Bond pair–bond pair repellents have a smaller effect on lone pair repulsions than do bond pair–lone pair repellents.

This means that there will be six lone-pair-bond pairings at 90 degrees, but there will be four at the same angle when both lone pairs of electrons are located at an angle of 45 degrees to the plane of the nucleus. Consequently, the second configuration is the most reliable.

Similar to the example before, the axial lone pair of electrons will have three lone pair-bond pair repulsions at 90 degrees while the other will have two lone pair-bond pairs at 90 degrees.

If one lone pair of electrons is in the axial position, there will be five 90-degree lone pair-bond pair repulsions. As with the T-shaped layout, this one is less stable than the others.

A bond angle (Cl-I-Cl) somewhat smaller than 90 degrees but more than 180 degrees is produced by the T-shape and trigonal bipyramidal geometry of iodine trichloride because of stronger repulsions between lone-pair pairs than between bond pairs.

Iodine’s hybridization in ICl3 will help us better grasp the chemical bonds in the molecule, so let’s get started.

Hybridization of ICl3 with other elements

To determine the hybridization of iodine in ICl3, the valence bond theory (VBT) is applied. It is known as hybridization when atomic orbitals of similar energy are combined and fused together to generate hybrid orbitals.

Depending on the number and presence of similar energy atomic orbitals, the hybridization of the central atom can be sp, sp2, sp3, sp3d, dsp2, or sp3d2.

Iodine’s ground state electrical configuration is [Kr] 4d105s25p5. Although there is only one unpaired electron, the creation of three bonds with three chlorine atoms requires the presence of three unpaired electrons.

To generate three bond pairs with three chlorine atoms, an electron from the 5p orbital will be promoted to the 5d orbital. [Kr] 4d105s25p45d1 is the excited-state electronic configuration of the iodide molecule.

In this case, a 5s orbital, three 5p orbitals, and one 5d orbital join and fuse together to generate five sp3d orbitals of the same energy level.

As a result, three of them will form sigma bonds with the chlorine atom’s 3p orbital. The electrons in two sp3d orbitals are coupled and operate as lone pairs in this structure.

As a result, iodine trichloride hybridization is sp3d and has trigonal bipyramidal geometry.

Iodine trichloride’s orbital diagram is shown below:

Detailed information about the Lewis structure can be found on the following YouTube page. Check it out!

Direction of Polarization of ICl3

The electronegativity difference between two atoms must be between 0.4 and 1.7 for a chemical bond to qualify as a polar covalent bond.

Iodine and chlorine have a Pauling scale electronegativity of 2.66 and 3.16, respectively. The Cl-I bond in iodine trichloride is polar because the electronegativity difference between iodine and chlorine is 0.5.

As a more electronegative element, chlorine will have a higher concentration of electrons.

The dipole moment from iodine to chlorine is permanent because of the electron density change towards chlorine.

As a result, dipole moments of two opposite Cl-I bonds will not cancel out since the angle between the lone pair-lone pair repulsions is greater than 180 degrees.

This bond’s total dipole moment is equal to the vector sum of its three individual dipole moments.

Therefore, iodine trichloride is a water-soluble molecule.


Because of the electronegativity difference between the two atoms, the Interhalogen complex ICl3 is more reactive than chlorine or iodine.

While chlorine has an eight-electron structure, iodine has an extended octet because of the d electrons present in ICl3’s Lewis structure.

Trigonal bipyramidal molecular geometry characterises ICl3. ICl3 has two lone pairs of electrons and three bond pairs. Since bond pairs repel each other, it is important to place the two lone pairs in the equatorial positions to ensure stability.

It is sp3d with trigonal bipyramidal shape that hybridises the iodine atom in ICl3.

Polarity was shown by the geometry and electronegativity differences between chlorine and an iodine atom.

As always, if you have any questions or concerns, please feel free to contact me. Thank you for your kind words.

Read more: Molecular Geometry, Hybridization and Polarity of BrF5 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.


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