Silicon tetraiodide Lewis Structure

Silicon tetraiodide Lewis Structure: I₄Si Lewis Structure, tetrahedral Geometry, sp3 Hybridization & Polarity

Silicon tetraiodide Key Facts

The Silicon tetraiodide Lewis structure is Si–I single bond, Si–I single bond, Si–I single bond and Si–I single bond; the central Si has 4 electron domains (0 lone pairs), giving a tetrahedral electron-domain arrangement and a tetrahedral molecular geometry with a 109.5° bond angle. Si is best described as sp3-hybridized, and Silicon tetraiodide is nonpolar because the bond dipoles cancel by molecular symmetry.

Figure 1: Lewis Structure of Silicon tetraiodide (I₄Si)

Chemical Formula	I₄Si
CAS Number	13465-84-4
Total Valence Electrons	32
Lewis Structure	Si–I single bond, Si–I single bond, Si–I single bond and Si–I single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	tetrahedral
Hybridization Model	sp3 (central Si)
Bond Angle	109.5°
Polarity	Nonpolar molecule

PubChem (CID 83498) and NIST list Silicon tetraiodide as I ₄Si with CAS 13465-84-4; molecular weight ≈ 535.703 g/mol. View CAS 13465-84-4 dictionary details on Guidechem →

Applications of Silicon tetraiodide (CAS 13465-84-4)

Silicon tetraiodide is encountered as a reagent, intermediate or specialty chemical in inorganic, organometallic and materials synthesis. Confirm grade, purity and supplier documentation (SDS) before specifying for a process.

Reagent / Intermediate Used in synthesis and formulation where the substance's reactivity is required.

Specialty Chemical Specified by grade for the intended process or research use.

Sourcing Verify purity, package and regional availability via the CAS identifier.

Procurement Note "Silicon tetraiodide" 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 13465-84-4 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Silicon tetraiodide Lewis structure we first count the total valence electrons. I₄Si contains 4×7 (I) + 4 (Si); the net charge of 0 gives a total of 32 valence electrons to place.

The central atom is Si. 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 = 4×7 (I) + 4 (Si) = 32 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place Si 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: Si–I single bond, Si–I single bond, Si–I single bond and Si–I single bond; no lone pairs on Si.

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

Si–I Si–I Si–I Si–I

Si: 0 lone pairs, 4 bonding domains

4 bonding domains + 0 lone pairs = 4 electron domains

Octet Rule: Why Si Has Eight Electrons Si forms 4 bond(s) and retains 0 nonbonding electron(s), reaching an octet. No expanded octet is required for this second-row (or octet-satisfying) central atom.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 4 electron domains around Si arrange to minimize mutual repulsion, giving an tetrahedral electron-domain geometry.

Because 0 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is tetrahedral; the Si bond angle is set to 109.5° 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 0 lone pair(s) on Si, 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, Si uses sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (4 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Si = V − N − ½B = 4 − 0 − ½×8 = 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: sp3 is a compact model for the 4 electron-domain directions around Si; full quantum-chemical treatments use molecular orbitals.

Is Silicon tetraiodide Polar or Nonpolar?

Silicon tetraiodide is nonpolar. Although individual Si–terminal bonds are polar when the atoms differ in electronegativity, the tetrahedral geometry makes their vector sum zero, so there is no net molecular dipole.

Expert Quote — Structural Chemistry Perspective

A common misconception is that polar bonds guarantee a polar molecule. Silicon tetraiodide shows the opposite: identical bond dipoles arranged with tetrahedral symmetry cancel exactly, yielding a nonpolar species.

Interpretation consistent with standard VSEPR / molecular-geometry references.

Its nonpolar character governs solvation and intermolecular behavior; specify grade and handling when sourcing.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
Silicon tetraiodide	I₄Si	Si	4	tetrahedral	Nonpolar
Silicon tetrafluoride	F₄Si	Si	4	tetrahedral	Nonpolar
Silane	H₄Si	Si	4	tetrahedral	Nonpolar

Practice question Starting from the 32 valence electrons of I₄Si, draw the Lewis structure and confirm the central Si atom is sp3-hybridized with tetrahedral 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 Silicon tetraiodide (CAS 13465-84-4)? Browse Supplier on Guidechem →

FAQs

Is I₄Si polar or nonpolar?

Silicon tetraiodide is nonpolar. Its tetrahedral symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Silicon tetraiodide?

Si–I single bond, Si–I single bond, Si–I single bond and Si–I single bond; no lone pairs on Si. It uses all 32 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Silicon tetraiodide?

The Si angle is about 109.5°. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of Si in Silicon tetraiodide?

The conventional model is sp3. Silicon tetraiodide has 4 electron domains around the central Si.

What is the CAS number of Silicon tetraiodide?

The CAS number is 13465-84-4. PubChem (CID 83498) and NIST identify this with I₄Si; use it to locate suppliers and database records.

References

PubChem CID 83498, Silicon tetraiodide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Silicon tetraiodide. Formula, CAS Registry Number and thermochemical / spectroscopic data.
IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Silicon tetraiodide (CAS 13465-84-4).

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 13465-84-4 identifies the substance, not a universal purity specification.

Make Guideview Preferred Source on Google

Silicon tetraiodide Lewis Structure