Phosphorus pentabromide Lewis Structure

Phosphorus pentabromide Lewis Structure: Br₅P Lewis Structure, trigonal bipyramidal Geometry, sp3d Hybridization & Polarity

Phosphorus pentabromide Key Facts

The Phosphorus pentabromide Lewis structure is P–Br single bond, P–Br single bond, P–Br single bond, P–Br single bond and P–Br single bond; the central P has 5 electron domains (0 lone pairs), giving a trigonal bipyramidal electron-domain arrangement and a trigonal bipyramidal molecular geometry with a 90° / 120° bond angle. P is best described as sp3d-hybridized, and Phosphorus pentabromide is nonpolar because the bond dipoles cancel by molecular symmetry.

Figure 1: Lewis Structure of Phosphorus pentabromide (Br₅P)

Chemical Formula	Br₅P
CAS Number	7789-69-7
Total Valence Electrons	40
Lewis Structure	P–Br single bond, P–Br single bond, P–Br single bond, P–Br single bond and P–Br single bond
Electron-Domain Geometry	trigonal bipyramidal
Molecular Geometry	trigonal bipyramidal
Hybridization Model	sp3d (central P)
Bond Angle	90° / 120°
Polarity	Nonpolar molecule

PubChem (CID 62678) and NIST list Phosphorus pentabromide as Br ₅P with CAS 7789-69-7; molecular weight ≈ 430.49 g/mol. View CAS 7789-69-7 dictionary details on Guidechem →

Applications of Phosphorus pentabromide (CAS 7789-69-7)

Phosphorus pentabromide 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 "Phosphorus pentabromide" 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 7789-69-7 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Phosphorus pentabromide Lewis structure we first count the total valence electrons. Br₅P contains 5×7 (Br) + 5 (P); the net charge of 0 gives a total of 40 valence electrons to place.

The central atom is P. 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 = 5×7 (Br) + 5 (P) = 40 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place P 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: P–Br single bond, P–Br single bond, P–Br single bond, P–Br single bond and P–Br single bond; no lone pairs on P.

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

P–Br P–Br P–Br P–Br P–Br

P: 0 lone pairs, 5 bonding domains

5 bonding domains + 0 lone pairs = 5 electron domains

Expanded Octet: d-Orbital Participation Central P belongs to period 3 or below, so it can accommodate more than eight electrons: low-lying d orbitals become available and the trigonal bipyramidal 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 P arrange to minimize mutual repulsion, giving an trigonal bipyramidal 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 trigonal bipyramidal; the P 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 0 lone pair(s) on P, 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, P uses sp3d hybrid orbitals to form the 5 equivalent electron-domain directions (5 bonding + 0 lone pair).

Formal-charge check

Formal charge on central P = V − N − ½B = 5 − 0 − ½×10 = 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 Phosphorus pentabromide use molecular orbitals and do not require populated d orbitals as the primary bonding picture.

Is Phosphorus pentabromide Polar or Nonpolar?

Phosphorus pentabromide is nonpolar. Although individual P–terminal bonds are polar when the atoms differ in electronegativity, the trigonal bipyramidal 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. Phosphorus pentabromide shows the opposite: identical bond dipoles arranged with trigonal bipyramidal 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
Phosphorus pentabromide	Br₅P	P	5	trigonal bipyramidal	Nonpolar
Phosphine	H₃P	P	4	trigonal pyramidal	Polar
Phosphorus trichloride	Cl₃P	P	4	trigonal pyramidal	Polar
Phosphorus pentachloride	Cl₅P	P	5	trigonal bipyramidal	Nonpolar
Phosphorus trifluoride	F₃P	P	4	trigonal pyramidal	Polar
Phosphorus pentafluoride	F₅P	P	5	trigonal bipyramidal	Nonpolar

Practice question Starting from the 40 valence electrons of Br₅P, draw the Lewis structure and confirm the central P atom is sp3d-hybridized with trigonal bipyramidal 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 Phosphorus pentabromide (CAS 7789-69-7)? Browse Supplier on Guidechem →

FAQs

Is Br₅P polar or nonpolar?

Phosphorus pentabromide is nonpolar. Its trigonal bipyramidal symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Phosphorus pentabromide?

P–Br single bond, P–Br single bond, P–Br single bond, P–Br single bond and P–Br single bond; no lone pairs on P. It uses all 40 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Phosphorus pentabromide?

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

What is the hybridization of P in Phosphorus pentabromide?

The conventional model is sp3d. Phosphorus pentabromide has 5 electron domains around the central P.

What is the CAS number of Phosphorus pentabromide?

The CAS number is 7789-69-7. PubChem (CID 62678) and NIST identify this with Br₅P; use it to locate suppliers and database records.

References

PubChem CID 62678, Phosphorus pentabromide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Phosphorus pentabromide. 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 Phosphorus pentabromide (CAS 7789-69-7).

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 7789-69-7 identifies the substance, not a universal purity specification.

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Phosphorus pentabromide Lewis Structure