Tetrachloroaluminate(III) ion Lewis Structure

Tetrachloroaluminate(III) ion Lewis Structure: AlCl₄ Lewis Structure, tetrahedral Geometry, sp3 Hybridization & Polarity

Tetrachloroaluminate(III) ion Key Facts

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

Figure 1: Lewis Structure of Tetrachloroaluminate(III) ion (AlCl₄)

Chemical Formula	AlCl₄
CAS Number	17992-87-1
Net Charge	-1
Total Valence Electrons	32
Lewis Structure	Al–Cl single bond, Al–Cl single bond, Al–Cl single bond and Al–Cl single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	tetrahedral
Hybridization Model	sp3 (central Al)
Bond Angle	109.5°
Polarity	Nonpolar molecule

PubChem and NIST list Tetrachloroaluminate(III) ion as AlCl ₄ with CAS 17992-87-1; molecular weight ≈ None g/mol. View CAS 17992-87-1 dictionary details on Guidechem →

Applications of Tetrachloroaluminate(III) ion (CAS 17992-87-1)

In aqueous and process chemistry, AlCl₄ exists as the anion Tetrachloroaluminate(III) ion ion. It is encountered as a counterion and a controlled source of Al in salts, buffers, electrochemistry and analytical protocols, and as a reactant in syntheses that require a defined equivalent of Al-containing material.

Ion Source / Counterion Supplied as salts and solutions; specify hydration, counter-cation and concentration.

Analytical & Electrochemical Used in titrations, plating baths and ionic-strength control where the ion is the active species.

Synthesis Reagent A controlled source of Al in precipitation, complexation and redox procedures.

Procurement Note "Tetrachloroaluminate(III) ion" 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 17992-87-1 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Tetrachloroaluminate(III) ion Lewis structure we first count the total valence electrons. AlCl₄ contains 3 (Al) + 4×7 (Cl) − 1 (net anion); the net charge of -1 gives a total of 32 valence electrons to place.

The central atom is Al. 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 (Al) + 4×7 (Cl) − 1 (net anion) = 32 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place Al 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: Al–Cl single bond, Al–Cl single bond, Al–Cl single bond and Al–Cl single bond; no lone pairs on Al.

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

Al–Cl Al–Cl Al–Cl Al–Cl

Al: 0 lone pairs, 4 bonding domains

4 bonding domains + 0 lone pairs = 4 electron domains

Octet Rule: Why Al Has Eight Electrons Al 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 Al 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 Al 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 Al, 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, Al uses sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (4 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Al = V − N − ½B = 3 − 0 − ½×8 = -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 Al; full quantum-chemical treatments use molecular orbitals.

Is Tetrachloroaluminate(III) ion Polar or Nonpolar?

Tetrachloroaluminate(III) ion is nonpolar. Although individual Al–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. Tetrachloroaluminate(III) ion 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
Tetrachloroaluminate(III) ion	AlCl₄	Al	4	tetrahedral	Nonpolar
Aluminum chloride	AlCl₃	Al	3	trigonal planar	Nonpolar

Practice question Starting from the 32 valence electrons of AlCl₄, draw the Lewis structure and confirm the central Al 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 Tetrachloroaluminate(III) ion (CAS 17992-87-1)? Browse Supplier on Guidechem →

FAQs

Is AlCl₄ polar or nonpolar?

Tetrachloroaluminate(III) ion is nonpolar. Its tetrahedral symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Tetrachloroaluminate(III) ion?

Al–Cl single bond, Al–Cl single bond, Al–Cl single bond and Al–Cl single bond; no lone pairs on Al. It uses all 32 valence electrons and the preferred structure carries a formal charge of -1 on the central atom.

What is the bond angle in Tetrachloroaluminate(III) ion?

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

What is the hybridization of Al in Tetrachloroaluminate(III) ion?

The conventional model is sp3. Tetrachloroaluminate(III) ion has 4 electron domains around the central Al.

What is the CAS number of Tetrachloroaluminate(III) ion?

The CAS number is 17992-87-1. PubChem and NIST identify this with AlCl₄; use it to locate suppliers and database records.

References

PubChem, Tetrachloroaluminate(III) ion. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Tetrachloroaluminate(III) ion. 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 Tetrachloroaluminate(III) ion (CAS 17992-87-1).

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 17992-87-1 identifies the substance, not a universal purity specification.

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Tetrachloroaluminate(III) ion Lewis Structure

Tetrachloroaluminate(III) ion Lewis Structure