selenium tetrabromide Lewis Structure

selenium tetrabromide Lewis Structure: Br₄Se Lewis Structure, seesaw Geometry, sp3d Hybridization & Polarity

selenium tetrabromide Key Facts

The selenium tetrabromide Lewis structure is Se–Br single bond, Se–Br single bond, Se–Br single bond and Se–Br single bond; the central Se has 5 electron domains (1 lone pair), giving a trigonal bipyramidal electron-domain arrangement and a seesaw molecular geometry with a ≈90° / 120° bond angle. Se is best described as sp3d-hybridized, and selenium tetrabromide is polar because the seesaw shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of selenium tetrabromide (Br₄Se)

Chemical Formula	Br₄Se
CAS Number	13465-40-0
Total Valence Electrons	34
Lewis Structure	Se–Br single bond, Se–Br single bond, Se–Br single bond and Se–Br single bond
Electron-Domain Geometry	trigonal bipyramidal
Molecular Geometry	seesaw
Hybridization Model	sp3d (central Se)
Bond Angle	≈90° / 120°
Polarity	Polar molecule

PubChem (CID 82246) and NIST list selenium tetrabromide as Br ₄Se with CAS 13465-40-0; molecular weight ≈ 398.59 g/mol. View CAS 13465-40-0 dictionary details on Guidechem →

Applications of selenium tetrabromide (CAS 13465-40-0)

selenium tetrabromide 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 "selenium tetrabromide" 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 13465-40-0 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the selenium tetrabromide Lewis structure we first count the total valence electrons. Br₄Se contains 4×7 (Br) + 6 (Se); the net charge of 0 gives a total of 34 valence electrons to place.

The central atom is Se. 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 (Br) + 6 (Se) = 34 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place Se 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: Se–Br single bond, Se–Br single bond, Se–Br single bond and Se–Br single bond; one lone pair on Se.

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

Se–Br Se–Br Se–Br Se–Br

Se: 1 lone pair, 4 bonding domains

4 bonding domains + 1 lone pairs = 5 electron domains

Expanded Octet: d-Orbital Participation Central Se belongs to period 3 or below, so it can accommodate more than eight electrons: low-lying d orbitals become available and the seesaw 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 Se arrange to minimize mutual repulsion, giving an trigonal bipyramidal electron-domain geometry.

Because 1 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is seesaw; the Se bond angle is set to ≈90° / 120° 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 1 lone pair(s) on Se, 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, Se uses sp3d hybrid orbitals to form the 5 equivalent electron-domain directions (4 bonding + 1 lone pair).

Formal-charge check

Formal charge on central Se = V − N − ½B = 6 − 2 − 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: sp3d / sp3d hybridization is a convenient localized-bond teaching model. Modern quantum-chemical descriptions of hypervalent selenium tetrabromide use molecular orbitals and do not require populated d orbitals as the primary bonding picture.

Is selenium tetrabromide Polar or Nonpolar?

selenium tetrabromide is polar. The seesaw 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 selenium tetrabromide the seesaw 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
selenium tetrabromide	Br₄Se	Se	5	seesaw	Polar
Selenium dioxide	O₂Se	Se	3	bent	Polar
Hydrogen selenide	H₂Se	Se	4	bent	Polar

Practice question Starting from the 34 valence electrons of Br₄Se, draw the Lewis structure and confirm the central Se atom is sp3d-hybridized with seesaw 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 selenium tetrabromide (CAS 13465-40-0)? Browse Supplier on Guidechem →

FAQs

Is Br₄Se polar or nonpolar?

selenium tetrabromide is polar. Its seesaw geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of selenium tetrabromide?

Se–Br single bond, Se–Br single bond, Se–Br single bond and Se–Br single bond; one lone pair on Se. It uses all 34 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in selenium tetrabromide?

The Se angle is about ≈90° / 120°. Lone-pair repulsion compresses the angle from the ideal trigonal bipyramidal value.

What is the hybridization of Se in selenium tetrabromide?

The conventional model is sp3d. selenium tetrabromide has 5 electron domains around the central Se.

What is the CAS number of selenium tetrabromide?

The CAS number is 13465-40-0. PubChem (CID 82246) and NIST identify this with Br₄Se; use it to locate suppliers and database records.

References

PubChem CID 82246, selenium tetrabromide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, selenium tetrabromide. 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 selenium tetrabromide (CAS 13465-40-0).

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 13465-40-0 identifies the substance, not a universal purity specification.

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selenium tetrabromide Lewis Structure

selenium tetrabromide Lewis Structure