Aluminum chloride Lewis Structure

Aluminum chloride Lewis Structure: AlCl₃ Lewis Structure, trigonal planar Geometry, sp2 Hybridization & Polarity

Aluminum chloride Key Facts

The Aluminum chloride Lewis structure is Al–Cl single bond, Al–Cl single bond and Al–Cl single bond; the central Al has 3 electron domains (0 lone pairs), giving a trigonal planar electron-domain arrangement and a trigonal planar molecular geometry with a 120° bond angle. Al is best described as sp2-hybridized, and Aluminum chloride is nonpolar because the bond dipoles cancel by molecular symmetry.

Figure 1: Lewis Structure of Aluminum chloride (AlCl₃)

Chemical Formula	AlCl₃
CAS Number	7446-70-0
Total Valence Electrons	24
Lewis Structure	Al–Cl single bond, Al–Cl single bond and Al–Cl single bond
Electron-Domain Geometry	trigonal planar
Molecular Geometry	trigonal planar
Hybridization Model	sp2 (central Al)
Bond Angle	120°
Polarity	Nonpolar molecule

PubChem (CID 24012) and NIST list Aluminum chloride as AlCl ₃ with CAS 7446-70-0; molecular weight ≈ 133.34 g/mol. View CAS 7446-70-0 dictionary details on Guidechem →

Applications of Aluminum chloride (CAS 7446-70-0)

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 "Aluminum chloride" 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 7446-70-0 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Aluminum chloride Lewis structure we first count the total valence electrons. AlCl₃ contains 3 (Al) + 3×7 (Cl); the net charge of 0 gives a total of 24 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) + 3×7 (Cl) = 24 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 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: 0 lone pairs, 3 bonding domains

3 bonding domains + 0 lone pairs = 3 electron domains

Octet Rule: Why Al Has Eight Electrons Al forms 3 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 3 electron domains around Al arrange to minimize mutual repulsion, giving an trigonal planar 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 planar; the Al bond angle is set to 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 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 sp2 hybrid orbitals to form the 3 equivalent electron-domain directions (3 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Al = V − N − ½B = 3 − 0 − ½×6 = 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: sp2 is a compact model for the 3 electron-domain directions around Al; full quantum-chemical treatments use molecular orbitals.

Is Aluminum chloride Polar or Nonpolar?

Aluminum chloride is nonpolar. Although individual Al–terminal bonds are polar when the atoms differ in electronegativity, the trigonal planar 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. Aluminum chloride shows the opposite: identical bond dipoles arranged with trigonal planar 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
Aluminum chloride	AlCl₃	Al	3	trigonal planar	Nonpolar
Carbon dioxide	CO₂	C	2	linear	Nonpolar
Carbon monoxide	CO	C	2	linear (diatomic)	Polar
Carbon disulfide	CS₂	C	2	linear	Nonpolar

Practice question Starting from the 24 valence electrons of AlCl₃, draw the Lewis structure and confirm the central Al atom is sp2-hybridized with trigonal planar 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 Aluminum chloride (CAS 7446-70-0)? Browse Supplier on Guidechem →

FAQs

Is AlCl₃ polar or nonpolar?

Aluminum chloride is nonpolar. Its trigonal planar symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Aluminum chloride?

Al–Cl single bond, Al–Cl single bond and Al–Cl single bond; no lone pairs on Al. It uses all 24 valence electrons and the preferred structure carries zero formal charge on the central atom.

What is the bond angle in Aluminum chloride?

The Al angle is about 120°. Lone-pair repulsion compresses the angle from the ideal trigonal planar value.

What is the hybridization of Al in Aluminum chloride?

The conventional model is sp2. Aluminum chloride has 3 electron domains around the central Al.

What is the CAS number of Aluminum chloride?

The CAS number is 7446-70-0. PubChem (CID 24012) and NIST identify this with AlCl₃; use it to locate suppliers and database records.

References

PubChem CID 24012, Aluminum chloride. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Aluminum chloride. 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 Aluminum chloride (CAS 7446-70-0).

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 7446-70-0 identifies the substance, not a universal purity specification.

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Aluminum chloride Lewis Structure