Bromotrichlorosilane Lewis Structure

Bromotrichlorosilane Lewis Structure: BrCl₃Si Lewis Structure, tetrahedral Geometry, sp3 Hybridization & Polarity

Bromotrichlorosilane Key Facts

The Bromotrichlorosilane Lewis structure is Si–Cl single bond, Si–Cl single bond, Si–Cl single bond and Si–Br 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 Bromotrichlorosilane is polar because the tetrahedral shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Bromotrichlorosilane (BrCl₃Si)

Chemical Formula	BrCl₃Si
CAS Number	2937-90-4
Total Valence Electrons	32
Lewis Structure	Si–Cl single bond, Si–Cl single bond, Si–Cl single bond and Si–Br single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	tetrahedral
Hybridization Model	sp3 (central Si)
Bond Angle	109.5°
Polarity	Polar molecule

PubChem (CID 83496) and NIST list Bromotrichlorosilane as BrCl ₃Si with CAS 2937-90-4; molecular weight ≈ 214.34 g/mol. View CAS 2937-90-4 dictionary details on Guidechem →

Applications of Bromotrichlorosilane (CAS 2937-90-4)

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 "Bromotrichlorosilane" 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 2937-90-4 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Bromotrichlorosilane Lewis structure we first count the total valence electrons. BrCl₃Si contains 7 (Br) + 3×7 (Cl) + 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 = 7 (Br) + 3×7 (Cl) + 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–Cl single bond, Si–Cl single bond, Si–Cl single bond and Si–Br 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–Cl Si–Cl Si–Cl Si–Br

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 Bromotrichlorosilane Polar or Nonpolar?

Bromotrichlorosilane is polar. The tetrahedral 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 Bromotrichlorosilane the tetrahedral 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
Bromotrichlorosilane	BrCl₃Si	Si	4	tetrahedral	Polar
Silicon tetrafluoride	F₄Si	Si	4	tetrahedral	Nonpolar
Silane	H₄Si	Si	4	tetrahedral	Nonpolar

Practice question Starting from the 32 valence electrons of BrCl₃Si, 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 Bromotrichlorosilane (CAS 2937-90-4)? Browse Supplier on Guidechem →

FAQs

Is BrCl₃Si polar or nonpolar?

Bromotrichlorosilane is polar. Its tetrahedral geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Bromotrichlorosilane?

Si–Cl single bond, Si–Cl single bond, Si–Cl single bond and Si–Br 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 Bromotrichlorosilane?

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 Bromotrichlorosilane?

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

What is the CAS number of Bromotrichlorosilane?

The CAS number is 2937-90-4. PubChem (CID 83496) and NIST identify this with BrCl₃Si; use it to locate suppliers and database records.

References

PubChem CID 83496, Bromotrichlorosilane. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Bromotrichlorosilane. 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 Bromotrichlorosilane (CAS 2937-90-4).

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 2937-90-4 identifies the substance, not a universal purity specification.

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Bromotrichlorosilane Lewis Structure

Bromotrichlorosilane Lewis Structure