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Iodine trichloride Lewis Structure

Iodine trichloride Lewis structure (Cl3I). I–Cl single bond, I–Cl single bond and I–Cl single bond. It shows a t-shaped shape, sp3d hybridization on I, ≈87.5° bond angles. Includes a comparison table and FAQs. Quinn3 MIN READSeptember 30, 2026

Iodine trichloride Lewis Structure: Cl3I Lewis Structure, T-shaped Geometry, sp3d Hybridization & Polarity

Iodine trichloride Lewis structure Cover

Iodine trichloride Key Facts

The Iodine trichloride Lewis structure is I–Cl single bond, I–Cl single bond and I–Cl single bond; the central I has 5 electron domains (2 lone pairs), giving a trigonal bipyramidal electron-domain arrangement and a T-shaped molecular geometry with a ≈87.5° bond angle. I is best described as sp3d-hybridized, and Iodine trichloride is polar because the T-shaped shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Iodine trichloride Lewis Structure Figure 1: Lewis Structure of Iodine trichloride (Cl3I)
Chemical Formula Cl3I
CAS Number 865-44-1
Total Valence Electrons 28
Lewis Structure I–Cl single bond, I–Cl single bond and I–Cl single bond
Electron-Domain Geometry trigonal bipyramidal
Molecular Geometry T-shaped
Hybridization Model sp3d (central I)
Bond Angle ≈87.5°
Polarity Polar molecule
PubChem (CID 70076) and NIST list Iodine trichloride as Cl 3I with CAS 865-44-1; molecular weight ≈ 233.26 g/mol. View CAS 865-44-1 dictionary details on Guidechem →

Applications of Iodine trichloride (CAS 865-44-1)

This organic compound is used as a solvent, intermediate or specialty reagent in fine-chemical, pharmaceutical and materials synthesis; specify grade and impurity profile when sourcing.

Solvent / Reagent Medium for reactions, extraction or formulation.
Intermediate Building block for downstream derivatives.
Specialty Use Targeted role in pharma/fragrance/materials.
Procurement Note "Iodine trichloride" is supplied in multiple commercial grades and package sizes. Specify purity, grade, moisture/impurity limits, package (cylinder, drum or bulk) and intended process, and use CAS 865-44-1 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Iodine trichloride Lewis structure we first count the total valence electrons. Cl3I contains 3×7 (Cl) + 7 (I); the net charge of 0 gives a total of 28 valence electrons to place.

The central atom is I. It is the least electronegative atom capable of forming multiple bonds and is surrounded by the more electronegative terminal atom(s); hydrogen, when present, always occupies a terminal position. Electronegativity considerations place the electron density toward the terminal atom(s).

Valence-electron count

Total valence electrons = 3×7 (Cl) + 7 (I) = 28 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place I at the center and connect each surrounding atom with a single bond, complete octets on the terminal atoms, and place any remaining electrons on the central atom. The resulting electron distribution is: I–Cl single bond, I–Cl single bond and I–Cl single bond; 2 lone pairs on I.

Counting bonding and nonbonding electrons around I therefore satisfies the octet/expanded-octet requirement for the drawn structure.

I–Cl I–Cl I–Cl
I: 2 lone pairs, 3 bonding domains
3 bonding domains + 2 lone pairs = 5 electron domains
Expanded Octet: d-Orbital Participation Central I belongs to period 3 or below, so it can accommodate more than eight electrons: low-lying d orbitals become available and the T-shaped arrangement with 5 domains reflects this expanded valence shell. The octet rule alone does not apply to such hypervalent species.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 5 electron domains around I arrange to minimize mutual repulsion, giving an trigonal bipyramidal electron-domain geometry.

Because 2 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is T-shaped; the I bond angle is set to ≈87.5° rather than the ideal value for the electron-domain geometry.

Repulsion hierarchy

A useful VSEPR approximation is: lone pair–lone pair repulsion > lone pair–bonding pair repulsion > bonding pair–bonding pair repulsion. With 2 lone pair(s) on I, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.

Hybridization & Formal Charge

In the conventional localized-bond model, I uses sp3d hybrid orbitals to form the 5 equivalent electron-domain directions (3 bonding + 2 lone pair).

Formal-charge check

Formal charge on central I = V − N − ½B = 7 − 4 − ½×6 = 0. The preferred Lewis structure carries zero formal charge on the central atom (and on the terminals), so it is the dominant contributor.

Modeling Note Modeling Note: sp3d / sp3d hybridization is a convenient localized-bond teaching model. Modern quantum-chemical descriptions of hypervalent Iodine trichloride use molecular orbitals and do not require populated d orbitals as the primary bonding picture.

Is Iodine trichloride Polar or Nonpolar?

Iodine trichloride is polar. The T-shaped shape prevents cancellation of the bond dipoles. The bond dipoles do not cancel, leaving a net molecular dipole, which strongly influences solvation behavior and intermolecular interactions.

Expert Quote — Structural Chemistry Perspective

The decisive structural fact is not simply that the individual bonds are polar; it is whether molecular symmetry allows their vector sum to vanish. In Iodine trichloride the T-shaped arrangement prevents cancellation, so a permanent dipole remains.

Interpretation consistent with standard VSEPR / molecular-geometry references.

This polarity profile underpins its behavior as a solvent, reactant or process intermediate; when sourcing, specify grade and container compatibility.

Structural Comparison Table

Species Formula Central Atom Electron Domains Molecular Geometry Polarity
Iodine trichloride Cl3I I 5 T-shaped Polar
Iodine trifluoride IF3 I 5 T-shaped Polar
Iodine pentafluoride IF5 I 6 square pyramidal Polar
Iodine heptafluoride IF7 I 7 pentagonal bipyramidal Nonpolar
Iodine I2 I 4 linear (diatomic) Nonpolar
Hydrogen iodide HI I 4 linear (diatomic) Polar
Practice question Starting from the 28 valence electrons of Cl3I, draw the Lewis structure and confirm the central I atom is sp3d-hybridized with T-shaped geometry. What happens to the bond angle if one terminal atom is replaced by a more electronegative substituent?
Looking for industrial bulk or specified-grade supplies of Iodine trichloride (CAS 865-44-1)? Browse Supplier on Guidechem →

FAQs

Is Cl3I polar or nonpolar?

Iodine trichloride is polar. Its T-shaped geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Iodine trichloride?

I–Cl single bond, I–Cl single bond and I–Cl single bond; 2 lone pairs on I. It uses all 28 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Iodine trichloride?

The I angle is about ≈87.5°. Lone-pair repulsion compresses the angle from the ideal trigonal bipyramidal value.

What is the hybridization of I in Iodine trichloride?

The conventional model is sp3d. Iodine trichloride has 5 electron domains around the central I.

What is the CAS number of Iodine trichloride?

The CAS number is 865-44-1. PubChem (CID 70076) and NIST identify this with Cl3I; use it to locate suppliers and database records.

References

  1. PubChem CID 70076, Iodine trichloride. Molecular formula, CAS number, molecular weight and chemical identity.
  2. NIST Chemistry WebBook, SRD 69, Iodine trichloride. Formula, CAS Registry Number and thermochemical / spectroscopic data.
  3. IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
  4. Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
  5. Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Iodine trichloride (CAS 865-44-1).

Technical scope: Lewis structures, VSEPR and hybridization are model-based descriptions for chemical communication and structure prediction; actual molecular electronic structure is more accurately represented by molecular-orbital and quantum-chemical methods. Commercial grades vary substantially by supplier and intended use; CAS 865-44-1 identifies the substance, not a universal purity specification.

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