ICl3 Lewis Structure: Drawings, Hybridization, Shape, Charges, Pairs

In this article, “icl3 lewis structure” different facts on ICl3 like lewis structure, hybridization, shape, formal charge calculation, stability and uses with detailed explanations are discussed briefly.

Iodine trichloride or ICl3 is a bright yellow colored interhalogen compound consisting with one iodine atom and three chlorine atoms. It is a T-shaped molecule with a sp3d hybridization. In the solid state it forms the dimer (I2Cl6) with two bridging chlorine atoms. This dimer has a planar structure.

Let’s have a look on the following topics on ICl3.

How to draw ICl3 lewis structure?

The name of this structural representation is lewis structure after the discovery of it by scientist Gilbert. N. Lewis in the year of 1916. One of the characteristics of this structure is that nonbonding electrons are shown around the respective atoms.

Drawing steps of lewis structure are described below-

  1. Determination of valance shell electron: Iodine (I) and chlorine (Cl) have same number of electrons that is seven in their valance shell.
  2. Determination of Bond and bonding electrons: In ICl3, total three covalent bonds are present. These bonds are between one iodine atom with the three chlorine atoms. Thus, total six electrons (each bond contains tow electrons) are involved as bonding electrons.
  3. Determination of nonbonding electrons:  Iodine has four nonbonding electrons or two pair of lone electrons and each of the chlorine atom has three pair or six nonbonding electrons. Thus, total number of nonbonding electrons in ICl3 are = {4 + (3×6)} = 22. These nonbonding electrons are written around the atoms.

ICl3 Lewis Structure Shape

Shape of any molecular species can be determined by hybridization of the central atom. How shape of any molecule is changed with the change of hybridization is shown below through the below chart.

Hybridization of central atom  Structure
sp Linear
sp2 Trigonal planar
sp3 Tetrahedral
sp3d Trigonal bipyramidal
sp3d2 Octahedral

But this chart can only be followed if any repulsion is absent in the molecule. Otherwise, the shape is deviated from its actual geometrical structure. Three types of repulsion can be present in any molecule. They are-

  • Lone pair-lone pair repulsion
  • Lone pair -bond pair repulsion
  • Bond pair-bond pair repulsion

The increasing order in the magnitude of the above repulsion is-

Bond pair-bond pair repulsion < Lone pair -bond pair repulsion < Bond pair-bond pair repulsion.

In ICl3, the above three types of repulsion of present due to having the lone pair of central atom (Iodin). From its hybridization (sp3d) it is predicted that the structure should be TBP (trigonal bipyramidal). But due to presence of repulsive factor it shows a T-shaped structure.

The two lone pair of iodin is placed in the equatorial position and rest of the position of TBP structure is substituted by three chlorine atoms (one equatorial and two axial position). According to VSEPR theory, lone pair should be placed in equatorial position due to greater stability.

Bond angle must be included to explain about shape of any molecule. This T-shaped structure shows the bond angle between Cl-I-Cl slightly greater than 1800 and smaller than 900 due to predominance of lone pair – lone pair repulsion over bond pair – bond pair repulsion.

ICl3 shape
Shape of ICl3

ICl3 Lewis Structure Formal Charge

Calculation of formal charge is very much significant is chemistry to identify the lewis structure having the lowest energy or greater stabilization factor. Formal charge calculation also helps to determine the charge of the individual atom present in the molecular species.

  • Formal charge = Total number of valance electrons – number of electrons remain as nonbonded – (number of electrons involved in bond formation/2)
  • Formal charge of iodine = 7 – 4 – (6/2) = 0
  • Formal charge of each of the chlorine atom = 7 – 6 – (2/2) = 0

As Cl is bonded with iodine through a single bond, so the bonding electrons for chlorine is 2. Iodine is connected with three chlorine atoms through three sigma bonds. Thus, bonding electrons of Iodine in ICl3 is 6 (3×2).

ICl3 Lewis Structure Bond Angle

Hybridization helps to find out the bond angle in any molecule. ICl3 has a T-shaped structure with two lone pair and three bond pair and sp3d hybridization.

The two lone pair are placed in the two equatorial position of TBP structure and three Cl atoms are in the two axial position and one equatorial position of TBP. Though the two lone pair placed in two axial position give the molecule lowest repulsion between them but the above described structure stabilizes the molecule most.

The angle between the two lone pairs will be 1200 (approximately) and slightly lesser than 900 with the two bond pairs and again 1200 to the rest of the bond pair placed in the equatorial position.

ICl3 Lewis Structure Octet Rule

Octet rule is described in chemistry as to have the electron configuration of any atom in their valance shell like their nearest noble gas. This special configuration gives the atom an extra stability.

In ICl3, octet rule is violated because iodine has more than eight electrons in its valance shell. It has seven valance electrons. After bonding with three Cl atoms, it gains three more electrons from the valance shell of Cl. Thus, the total electron of iodine in ICl3 becomes 10 (7+3). This electron configuration does not resemble with the nearest noble gas (Xe) electron configuration (5s2 5p6).

Chlorine atoms are not violating octet rule because they have seven electrons in their outer most shell and after forming bond with Iodine they gain one more electron in their valance shell. Thus, the total number of valance shell electron becomes eight which matches with the nearest noble gas (Ne) electron configuration (2s2 2p6) in periodic table.

ICl3 Lewis Structure Lone Pairs

There are few electron or electron pairs in the lewis structure (represented as electron dot), who are not involved in bond formation with another molecule. These electrons are called nonbonding electrons and the electron pairs are known as lone pair. Lone pair electrons are also the valance electron of the atoms.

  • Nonbonded electron = Total number of valance electron – number of bonded electrons.
  • Nonbonding electrons on Iodine (I) = 7 – 3 = 4 or 2 lone pair
  • Nonbonding electrons on each of the chlorine atoms (Cl) = 7 – 1 = 6 or three lone pairs.

As both the iodine and chlorine are halogen compound, they have equal number of (seven) electrons in their valance shell (ns2 np5).

Thus, the total nonbonding electrons in ICl3 = {4 + (3×6)} = 22 or 11 pair of lone electrons.

ICl3 Valence Electrons

Valance electrons are basically the outer most shell electrons of any atom. In most of the cases valance electrons participate in chemical reaction due to availability of them rather than the inner shell electrons because the attraction of nucleus on valance shell is the least with comparing to inner shell electrons.

In this interhalogen compound, ICl3, both the participating atoms (iodine and chlorine) have same number of valance electrons. They both have seven electrons in their respective valance shell. The valance shell electron configuration of chlorine and iodine are 3s2 3p5 and 5s2 5p5 respectively.

Thus, total number of valance electrons in ICl3 = {7 + (3×7)} = 28

ICl3 Hybridization

When two or more than two orbitals having comparable size, energy difference mix up with each other, then it is called hybridization. Determination of hybridization of central atom has different significance in chemistry, mainly in structure or shape determination of any molecule.

ICl3 Hybridization
Hybridization of ICl3

From the hybridization the predicted structure is trigonal bipyramidal. But due to the repulsion the actual geometrical structure is deviated and the shape of the molecule becomes T-shaped.

Is ICl3 ionic or covalent?

The main difference between a covalent compound and ionic compound is that in covalent compound valance electrons are shared between the atoms and in ionic compound valance electrons are donated from one atom to another atom. In covalent compound the sharing of electron does not happen equally. More electronegative atom is attracted the electrons more towards itself than less electronegative atom.

ICl3 is definitely a covalent compound. Three covalent bons are present between iodine and three chlorine atoms. Some of the great evidences of the covalency of ICl3 are-

  • Smaller electronegativity difference between iodine and chlorine. The electronegativity of iodine and chlorine are 2.66 and 3.16 in Pauling scale respectively.
  • Both the iodine and chlorine are nonmetal.
  • Valance electrons of iodine and chlorine are not donated from iodine to chlorine rather it is shared between these two atoms.

Is ICl3 stable?

ICl3 is comparatively reactive than the normal halogen compound I2. The reason behind this reactivity is that the I-Cl bond is weaker due to electronegativity difference between iodine and chlorine.

But ICl3 is more stable than the other interhalogen compound because the large size of iodine. The large size reduces its reactivity and makes the molecule stable with comparing to the other interhalogen compound.

ICl3 Uses

Iodine trichloride (ICl3) is an interhalogen compound and it has different uses in industry like-

  • It is used as chlorinating agent in organic synthesis.
  • It is also used as iodinating agent to insert iodine into organic compounds for the production of their halogen derivatives.

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