Al3+ Lewis Structure, Geometry: 17 Facts You Should Know

Al3+ is a cation of aluminium which has fewer electrons than normal real aluminium metal.

In article we are learning about Al3+ lewis structure. Aluminium is the metal belongs to the 13th group of the periodic table. It means Al has three electrons in its outer valence shell. Al3+ ion is produced by the reduction of three electrons from Al metal. Let us discuss the detailed Al3+ structure, geometry and its various facts.

How to draw Al3+ lewis structure?

The aluminium metal is belongs to the thirteenth group of periodic table, which confirms the presence of three valence electrons in its outer valence shell. Aluminium metal has atomic number 13. Thus the aluminium metal has 13 electrons. The electronic configuration for Al metal is as follows:

Al (13) – 1s2, 2s2, 2p6, 3s2, 3p1 or [Ne]10 3s2 3p1

The Al3+ ion is produced by the decrease in electrons in aluminium metal, so Al3+ ion consists of only ten electrons in it and its outer shell being similar to neon. Thus, it has total 10 valence electrons in Al3+ ion. So, the electronic configuration of Al3+ ion is as follows:

Al3+ (10) – 1s2, 2s2, 2p6 Or [Ne]10 3s1

Due to the loss or donation of three electrons by Al metal, the tripositive (3+) charge gets creates on Al metal. So the Al metal shows under the square bracket with the 3+ charge on it. Actually Al3+ is just only shows the lewis symbol but Al3+ lewis structure is not possible to draw because Al is just only an atom.

Al3+ valence electrons

The Al3+ ion has total eight valence electrons. Al atom has total 13 valence electrons from which it donates 3 electrons to form Al3+ tripositive ion. As, the Al atom belongs to 13th group of periodic table so it has 3 valence electrons in its valence shell. But in Al3+ ion it has three fewer electrons, so it has total ten electrons in Al3+ ion as shown in following figure:

al3+ lewis structure
Valence electrons in Al3+

Al3+ lewis structure formal charge

To calculate formal charge on any element of lewsi structure we have a formula:

Formal charge = (valence electrons – non-bonding electrons – ½ bonding electrons)

Al3+ ion formal charge calculation is a s follows:

Aluminium atom: Valence electrons on aluminium atom = 08

                            Non-bonding electrons on aluminium atom = 03

                            Bonding electrons with aluminium atom =00

Formal charge on aluminium Al atom is = (08 – 08 – 0/2)          

Thus, aluminium atom has zero formal charge on it.

Actually, it is not possible to calculate formal charge of any single atom anion or cation as there is no bonding and non-bonding electrons are present on it.

Al3+ lewis structure octet rule

As aluminium atom has total 13 electrons present on it and so having 3 valence electrons. So the Al metal which has only 3 electrons in its last shell having incomplete octet. Similarly, Al3+ ion has total 10 electrons present on it, so having 8 valence electrons. As the Al3+ ions have eight valence electrons in its valence shell orbital, so the Al3+ ion has a complete octet.

Al3+ lewis structure lone pairs

The Al3+ ion has total 10 electrons and having 8 electrons in its valence shell. Means it has total eight non- bonding electrons present on it i.e. eight electrons are available on Al3+ ion for sharing or bonding with other elements or atoms.

So, if we pair up two electrons to make them electron pair for bonding and sharing with other elements or atoms. We will get total four pairs of non- bonding electrons present on it. Thus, the Al3+ lewis structure or ion has total four lone pair electrons present on it.

Is Al3+ an ion?

Yes Al3+ is an ion i.e. cation in nature. As the Al atom belongs to 13th group of periodic table and has total thirteen electrons present on it with three valence electrons. So, the three valence electrons are available for sharing or bonding with other atoms or elements. If the Al atom donates its three outer shell valence electrons to other atoms, it will remain with only ten electrons.

As the Al atom losses it three electron, there will be a tri- positive charge creates on it, converting the Al atom into Al3+ ion. As there is the positive charge creates on Al atom due to loss of electrons, so Al3+ ion is a cation.

Al 2
Al3+ as an cation

Al3+ lewis structure resonance

The resonance structure of Al3+ ion is not possible as there is no other atom or element is attached to it. Al3+ ion is a single element ion which has tri- positive charge present on it with complete octet as it has eight valence electrons in its outer valence shell. So, Al3+ ion can not show any resonance structure of it.

Al 4
Comparative structure of Al and Al3+

Al3+ lewis structure shape

Al3+ ion has no shape. As the Al3+ ion is a single atom cation with tri- positive charge on it and it has four lone electron pairs for bonding with other atoms. But as the Al3+ is just an ion it is not attached with other atoms so it doesn’t becomes a molecule.

Even it doesn’t have any bonds or bonding electrons, so it can’t bent or linear or do not orient towards anywhere. As it has not attached with other elements, there is no electron cloud density present on it and no comparisons of electronegativity of two or more than two elements.

Al3+ lewis structure angle

Al3+ is the single element ion and don’t have any other elements attached with it. Even it doesn’t have any kind of deviation towards electron cloud density of other atoms. Also there is no comparison of electronegativities between two or more atoms or elements. So, there is no any angle present in Al3+ lewis structure or Al3+ ion.

Al3+ hybridization

Al3+ ion originally don’t have any hybridization as it is just a single element ion. Hybridization occurs with the mixing and recasting of atomic orbitals of any molecule consists of two or more atoms in it. But in case of Al3+ ion there is no other elements are present rather than aluminium and also there is no bonding form within the ion.

So, alone Al3+ ion can’t show any kind of hybridization. But Al3+ ion can form complex compounds when AlCl3 reacted with aqueous acids forms a complex compound like [Al(H2O)6]3+. In complex compounds like this, Al3+ ion has sp3d2 hybridization.

Al3+ solubility

Al3+ ion is soluble in following list:

  • Bromides (Br)
  • Chlorides (Cl)
  • Chlorates (ClO3)
  • Nitrates (NO3)
  • Sulphates (SO42-)

Al3+ ion is insoluble in following list:

  • Carbonates (CO32-)
  • Hydroxides (OH)
  • Oxides (O2-)
  • Phosphates (PO43-)
  • Dichromates (Cr2O72-)

Is Al3+ polyatomic?

No, Al3+ is not a polyatomic ion as it is consists of only one atom or element. Polyatomic means the compound which contains two or more than two atoms in its compound. But Al3+ ion doesn’t have any other atom in its Al3+ lewis structure. So, it is not a polyatomic ion. As forming compound with other atoms Al3+ ion can form polyatomic molecules.

Is Al3+ acidic or basic?

Al3+ ion is a high charge containing small ion, so it has the density of very high charge and great polarising power. When reacts with water it will take OH- ions from water and creating More H+ ions in the solution.

Al3+ metal ions acidity strength is related to its capability to attract the electron towards itself i.e. behaves as oxidising agent. The metal ion acidity strength is as in the order Al3+ > Mg2+ > Na+.

So, it acts as a lewis acid in water and also can produce aqua complex ions in it. Also Al3+ ion can act as a lewis base as it can accepts pair of electrons from water to form aqua complex.

Is al3+ paramagnetic or diamagnetic?

Compounds or atoms containing unpaired electrons in its valence shell are considered as a paramagnetic compound and the compounds or atoms which have completely paired electrons are considered as diamagnetic compounds. Magnetic field affects paramagnetic compounds but the magnetic field doesn’t affect diamagnetic compounds.

In aluminium metal there is a loss of three electrons from its valence shell, so there are remaining ten electrons forming Al3+ ion. So, the electronic configuration of Al3+ ion is:

Al3+ = 1s2, 2s2, 2p6

Al 6
Electronic configuration of Al3+ ion

From the above electronic configuration of Al3+ ion we can see that there are all completely paired electrons are present in 2p6 orbital of Al3+ ion, so it is diamagnetic in nature.

Is Al3+ isoelectronic with neon?

Isoelectronic means the molecule or atom or ions having equal or same number of electrons are isoelectronic with each other.

The electronic configuration of neon and Al3+ ion are as follows:

Ne = 1s2, 2s2, 2p6 or [He] 2s2, 2p6

Al3+ = 1s2, 2s2, 2p6 or [Ne] 2s2, 2p6

As we can see from the above electronic configuration of Neon and Al3+ ion both have same number of electrons present in their outer valence orbitals i.e. ten electrons are present in both neon and Al3+ ion so they are isoelectronic with each other.


Al3+ ions have 3 less electrons than original Al metal and have a tri- positive charge on it having 8 valence electrons in its outer shell. It has complete octet with four lone electron pair. It is a cation and isoelectronic with neon atom. It also shows diamagnetic nature as it has completely paired electrons.

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