The Aluminum ion Lewis structure is central Al bonded; the central Al has 0 electron domains (0 lone pairs), giving a tetrahedral electron-domain arrangement and a see text molecular geometry with a — bond angle. Al is best described as sp3-hybridized, and Aluminum ion is polar because the see text shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.
Figure 1: Lewis Structure of Aluminum ion (Al+3)
| Chemical Formula | Al+3 |
| CAS Number | 22537-23-1 |
| Net Charge | +3 |
| Total Valence Electrons | 0 |
| Lewis Structure | central Al bonded |
| Electron-Domain Geometry | tetrahedral |
| Molecular Geometry | see text |
| Hybridization Model | sp3 (central Al) |
| Bond Angle | — |
| Polarity | Polar molecule |
In aqueous and process chemistry, Al+3 exists as the cation Aluminum 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.
To draw the Aluminum ion Lewis structure we first count the total valence electrons. Al+3 contains 3 (Al) + 3 (net cation); the net charge of +3 gives a total of 0 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).
Total valence electrons = 3 (Al) + 3 (net cation) = 0 electrons.
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; no lone pairs on Al.
Counting bonding and nonbonding electrons around Al therefore satisfies the octet/expanded-octet requirement for the drawn structure.
VSEPR theory states that the 0 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 see text; the Al bond angle is set to — rather than the ideal value for the electron-domain geometry.
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.
In the conventional localized-bond model, Al uses sp3 hybrid orbitals to form the 0 equivalent electron-domain directions (0 bonding + 0 lone pair).
Formal charge on central Al = V − N − ½B = 3 − 0 − ½×0 = 3. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.
Aluminum ion 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.
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 ion 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.
| Species | Formula | Central Atom | Electron Domains | Molecular Geometry | Polarity |
|---|---|---|---|---|---|
| Aluminum ion | Al+3 | Al | 0 | see text | Polar |
| Aluminum chloride | AlCl3 | Al | 3 | trigonal planar | Nonpolar |
Aluminum ion is polar. Its see text geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.
central Al bonded; no lone pairs on Al. It uses all 0 valence electrons and the preferred structure carries a formal charge of 3 on the central atom.
The Al angle is about —. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.
The conventional model is sp3. Aluminum ion has 0 electron domains around the central Al.
The CAS number is 22537-23-1. PubChem (CID 104727) and NIST identify this with Al+3; use it to locate suppliers and database records.
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 22537-23-1 identifies the substance, not a universal purity specification.
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