Iron(III) bromide Lewis Structure

Iron(III) bromide Lewis Structure: Br₃Fe Lewis Structure, see text Geometry, sp3 Hybridization & Polarity

Iron(III) bromide Key Facts

The Iron(III) bromide Lewis structure is central Br bonded; the central Br has 4 electron domains (4 lone pairs), giving a tetrahedral electron-domain arrangement and a see text molecular geometry with a — bond angle. Br is best described as sp3-hybridized, and Iron(III) bromide is polar because the see text shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Iron(III) bromide (Br₃Fe)

Chemical Formula	Br₃Fe
CAS Number	10031-26-2
Total Valence Electrons	21
Lewis Structure	central Br bonded
Electron-Domain Geometry	tetrahedral
Molecular Geometry	see text
Hybridization Model	sp3 (central Br)
Bond Angle	—
Polarity	Polar molecule

PubChem (CID 82310) and NIST list Iron(III) bromide as Br ₃Fe with CAS 10031-26-2; molecular weight ≈ 295.56 g/mol. View CAS 10031-26-2 dictionary details on Guidechem →

Applications of Iron(III) bromide (CAS 10031-26-2)

Interhalogen fluorides such as Iron(III) bromide are exceptionally vigorous fluorinating and oxidizing agents. They are employed in uranium processing, in the fluorination of metals, ceramics and polymers, and as rocket oxidizers. Their reactivity with water and organics is extreme, so they are handled only in passivated, dry systems.

Fluorinating Agent Converts metals and refractory materials to volatile fluorides for separation and processing.

Oxidizer High-energy oxidizer role in specialized propulsion and synthesis.

Handling Extreme moisture/organics sensitivity; strictly anhydrous, passivated equipment.

Procurement Note "Iron(III) bromide" 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 10031-26-2 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Iron(III) bromide Lewis structure we first count the total valence electrons. Br₃Fe contains 3×7 (Br); the net charge of 0 gives a total of 21 valence electrons to place.

The central atom is Br. 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 (Br) = 21 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place Br 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: central Br bonded; 4 lone pairs on Br.

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

Br: 4 lone pairs, 0 bonding domains

0 bonding domains + 4 lone pairs = 4 electron domains

Octet Rule: Why Br Has Eight Electrons Br forms 0 bond(s) and retains 8 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 Br arrange to minimize mutual repulsion, giving an tetrahedral electron-domain geometry.

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

Formal-charge check

Formal charge on central Br = V − N − ½B = 7 − 8 − ½×0 = -1. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp3 is a compact model for the 4 electron-domain directions around Br; full quantum-chemical treatments use molecular orbitals.

Is Iron(III) bromide Polar or Nonpolar?

Iron(III) bromide is polar. The see text 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 Iron(III) bromide the see text 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
Iron(III) bromide	Br₃Fe	Br	4	see text	Polar
Bromine trifluoride	BrF₃	Br	5	T-shaped	Polar
Hydrogen bromide	HBr	Br	4	linear (diatomic)	Polar

Practice question Starting from the 21 valence electrons of Br₃Fe, draw the Lewis structure and confirm the central Br atom is sp3-hybridized with see text 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 Iron(III) bromide (CAS 10031-26-2)? Browse Supplier on Guidechem →

FAQs

Is Br₃Fe polar or nonpolar?

Iron(III) bromide is polar. Its see text geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Iron(III) bromide?

central Br bonded; 4 lone pairs on Br. It uses all 21 valence electrons and the preferred structure carries a formal charge of -1 on the central atom.

What is the bond angle in Iron(III) bromide?

The Br angle is about —. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of Br in Iron(III) bromide?

The conventional model is sp3. Iron(III) bromide has 4 electron domains around the central Br.

What is the CAS number of Iron(III) bromide?

The CAS number is 10031-26-2. PubChem (CID 82310) and NIST identify this with Br₃Fe; use it to locate suppliers and database records.

References

PubChem CID 82310, Iron(III) bromide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Iron(III) bromide. 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 Iron(III) bromide (CAS 10031-26-2).

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 10031-26-2 identifies the substance, not a universal purity specification.

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Iron(III) bromide Lewis Structure