Aluminum Lewis Structure

Aluminum Lewis Structure: Al Lewis Structure, see text Geometry, sp Hybridization & Polarity

Aluminum Key Facts

The Aluminum Lewis structure is central Al bonded; the central Al has 2 electron domains (1 lone pair), giving a linear electron-domain arrangement and a see text molecular geometry with a — bond angle. Al is best described as sp-hybridized, and Aluminum is polar because the see text shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Aluminum (Al)

Chemical Formula	Al
CAS Number	7429-90-5
Total Valence Electrons	3
Lewis Structure	central Al bonded
Electron-Domain Geometry	linear
Molecular Geometry	see text
Hybridization Model	sp (central Al)
Bond Angle	—
Polarity	Polar molecule

PubChem (CID 5359268) and NIST list Aluminum as Al with CAS 7429-90-5; molecular weight ≈ 26.981538 g/mol. View CAS 7429-90-5 dictionary details on Guidechem →

Applications of Aluminum (CAS 7429-90-5)

Aluminum 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 "Aluminum" 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 7429-90-5 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 Lewis structure we first count the total valence electrons. Al contains 3 (Al); the net charge of 0 gives a total of 3 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 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: central Al bonded; one lone pair on Al and one unpaired electron on Al.

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

Al: 1 lone pair, 0 bonding domains

0 bonding domains + 1 lone pairs = 2 electron domains

Octet Rule: Why Al Has Eight Electrons Al forms 0 bond(s) and retains 2 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 2 electron domains around Al arrange to minimize mutual repulsion, giving an linear 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 see text; the Al 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 1 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 sp hybrid orbitals to form the 2 equivalent electron-domain directions (0 bonding + 1 lone pair).

Formal-charge check

Formal charge on central Al = V − N − ½B = 3 − 2 − 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: sp is a compact model for the 2 electron-domain directions around Al; full quantum-chemical treatments use molecular orbitals.

Is Aluminum Polar or Nonpolar?

Aluminum 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 Aluminum 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
Aluminum	Al	Al	2	see text	Polar
Aluminum chloride	AlCl₃	Al	3	trigonal planar	Nonpolar

Practice question Starting from the 3 valence electrons of Al, draw the Lewis structure and confirm the central Al atom is sp-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 Aluminum (CAS 7429-90-5)? Browse Supplier on Guidechem →

FAQs

Is Al polar or nonpolar?

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

What is the Lewis structure of Aluminum?

central Al bonded; one lone pair on Al and one unpaired electron on Al. It uses all 3 valence electrons and the preferred structure carries a formal charge of 1 on the central atom.

What is the bond angle in Aluminum?

The Al angle is about —. Lone-pair repulsion compresses the angle from the ideal linear value.

What is the hybridization of Al in Aluminum?

The conventional model is sp. Aluminum has 2 electron domains around the central Al.

What is the CAS number of Aluminum?

The CAS number is 7429-90-5. PubChem (CID 5359268) and NIST identify this with Al; use it to locate suppliers and database records.

References

PubChem CID 5359268, Aluminum. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Aluminum. 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 (CAS 7429-90-5).

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 7429-90-5 identifies the substance, not a universal purity specification.

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Aluminum Lewis Structure