Aluminium Formula: Aluminium is a very important and strategic metal. Do you know? It is the most abundant metal in the earth’s crust. About \(8 \%\) of our Earth’s crust is composed of aluminium. It is a silvery-white metallic element with the symbol \(\text {Al}\). In this article, we are going to discuss more about aluminium \((\text {Al})\).

What is Aluminium (Al)?

Aluminium is a chemical element with atomic number \(13\). Its chemical symbol is \(\text {Al}\). It is present in group \(13\) and period \(3\) of the periodic table. The electronic configuration of aluminium is \({\text{1}}{{\text{s}}^{\text{2}}}{\text{,}}\,{\text{2}}{{\text{s}}^{\text{2}}}{\text{,2}}{{\text{p}}^{\text{6}}}{\text{,3}}{{\text{s}}^{\text{2}}}{\text{,3}}{{\text{p}}^{\text{1}}}\). It generally exhibits \(+3\) oxidation state. The atomic mass of aluminium is \(26.98\,\text {u}\). Aluminium valency is +3.

Occurrence of Aluminium

Aluminium is the third most abundant element after oxygen and silicon by weight in the earth crust. Aluminium is majorly found in nature as bauxite, \(\mathrm{Al}_{2} \mathrm{O}_{3} \cdot 2 \mathrm{H}_{2} \mathrm{O}\). Aluminium also occurs in large amounts in aluminosilicate rocks such as feldspar or orthoclase \(\left(\mathrm{KAlSi}_{3} \mathrm{O}_{8}\right)\), mica \(\left(\mathrm{K}_{2} \mathrm{O} .2 \mathrm{H}_{2} \mathrm{O} .3 \mathrm{Al}_{2} \mathrm{O}_{3} \cdot 6 \mathrm{SiO}_{2}\right)\), beryl \(\left(\mathrm{Be}_{3} \mathrm{Al}_{2} \mathrm{Si}_{6} \mathrm{O}_{18}\right)\), garnet \(\left[\mathrm{Ca}_{3} \mathrm{Al}_{2}\left(\mathrm{SiO}_{4}\right)_{3}\right]\) and minerals such as cryolite \(\left(\mathrm{Na}_{3} \mathrm{AlF}_{6}\right)\) and corundum \(\left(\mathrm{Al}_{2} \mathrm{O}_{3}\right)\). In India, aluminium is majorly found as mica in Madhya Pradesh, Karnataka, Orissa and Jammu Kashmir.

Physical Properties of Aluminium

Let us discuss some physical properties of aluminium.

Aluminium metal is silvery-white in appearance. It is a soft and light metal. It is non-toxic and corrosion resistant too. It has high thermal and electrical conductance. It has an extremely low density. Aluminium is insoluble in cold water and organic solvents. It is readily soluble in dilute hydrochloric acid and in alkalis. The melting and boiling point of aluminium are \(933\,\text {K}\) and \(2740\,\text {K}\) respectively.

Chemical Properties of Aluminium

Let us discuss some chemical properties of aluminium.

Reaction of Aluminium with Acids

Aluminium reacts with different acids as,

1. Reaction with Hydrochloric Acid

Aluminium reacts with dilute hydrochloric acid to form aluminium chloride and hydrogen gas. That is,

\(2 \mathrm{Al}+6 \mathrm{HCl} \rightarrow 2 \mathrm{AlCl}_{3}+3 \mathrm{H}_{2}\)

2. Reaction with Sulphuric Acid

Aluminium reacts with dilute sulphuric acid to form aluminium sulphate along with the liberation of hydrogen gas (the gas evolved will be at a slow rate). That is,

\(2 \mathrm{Al}+\underset{\text { Dilute }}{3 \mathrm{H}_{2} \mathrm{SO}_{4}} \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{H}_{2}\)

In hot concentrated sulphuric acid, aluminium dissolves in it forming aluminium sulphate, water along with the evolution of sulphur dioxide. That is,

\(2 \mathrm{Al}+\underset{\text { Concentrated }}{6 \mathrm{H}_{2} \mathrm{SO}_{4}} \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+3 \mathrm{SO}_{2}+6 \mathrm{H}_{2} \mathrm{O}\)

3. Reaction with Nitric Acid

Aluminium reacts with dilute nitric acid to form aluminium nitrate and ammonium nitrate. That is,

\(8 \mathrm{Al}+30 \mathrm{HNO}_{3} \rightarrow 8 \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}+9 \mathrm{H}_{2} \mathrm{O}+3 \mathrm{NH}_{4} \mathrm{NO}_{3}\)

When aluminium is treated with concentrated nitric acid, a layer of metal oxides is formed on the surface the metal which prevents the further action or the metal becomes passive. Hence, concentrated nitric acid can be transported in aluminium containers.

Reaction of Aluminium with Alkalis

Aluminium, when treated with hot alkalis, it forms metaaluminate and hydrogen. That is,

\(2 \mathrm{Al}+2 \mathrm{NaOH}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow \underset{\text { Sodium metaaluminate }}{2 \mathrm{NaAlO}_{2}}+3 \mathrm{H}_{2}\)

\(2 \mathrm{Al}+\mathrm{OH}^{-}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{AlO}_{2}^{-}+3 \mathrm{H}_{2} \uparrow\)

Reaction of Aluminium with Halogens

Aluminium reacts with halogens to form the respective halides. For example, aluminium reacts with chlorine to form aluminium chloride. That is,

\(2 \mathrm{Al}+3 \mathrm{Cl}_{2} \rightarrow 2 \mathrm{AlCl}_{3}\)

Similarly, aluminium reacts with bromine to form aluminium bromide \((\text {AlBr}_{3})\), aluminium reacts iodine to form aluminium iodide \(\left(\mathrm{AlI}_{3}\right)\) and it reacts with fluorine aluminium fluoride \(\left(\mathrm{AIF}_{3}\right)\).

Reaction of Aluminium with Air

Aluminium reacts with oxygen to form a protective layer of aluminium (III) oxide that prevents further reaction with oxygen. This is the reason why aluminium is called as a corrosion-resistant metal.

Aluminium burns in oxygen with a brilliant white flame. The product in this reaction is also aluminium (III) oxide. That is,

\(4 \mathrm{Al}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{Al}_{2} \mathrm{O}_{3}\)

Uses of Aluminium

Aluminium has got so many uses. They include:

1. Being cheap and corrosion resistant, aluminium is used for making cooking utensils, picture frames, household fittings, etc.
2. Aluminium is a good conductor of electricity. Therefore, it is used for making electric transmission cables and wires.
3. Powdered aluminium is used as a silvery white paint for iron poles because it prevents their corrosion.
4. Aluminium foil is used for packaging food stuffs, soaps, cigarettes, etc.
5. A mixture of aluminium powder and ammonium nitrate is used as an explosive under the name ammonal.
6. Aluminium is used I the extraction of metals.
7. It is used in alloy making.

Different Compounds of Aluminium

Aluminium forms a variety of compounds. Let us discuss some of the

Aluminium Sulphate Formula

Aluminium sulphate is a chemical compound with the formula \(\mathrm{Al}{2}\left(\mathrm{SO}{4}\right)_{3}\). It is an inorganic compound. It is also known as filter alum or dialuminium trisulphate. Let us discuss more about aluminium sulphate.

Aluminium Sulphate Al₂(SO₄)₃

Aluminium sulphate is an ionic compound. It contains two aluminium \(\left(\mathrm{Al}^{3+}\right)\) ions and three sulphate \(\left(\mathrm{SO}_{4}^{2-}\right)\) ions. Aluminium sulphate can be represented as,

Preparation of Aluminium Sulphate

Aluminium sulphate is an inorganic salt formed by the reaction of sulphuric acid with aluminium hydroxide.  That is,

\(2 \mathrm{Al}(\mathrm{OH})_{3}+3 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+6 \mathrm{H}_{2} \mathrm{O}\)

Aluminium sulphate is produced when the metal aluminium reacts with sulphuric acid solution. That is,

\(2 \mathrm{Al}+3 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}+3 \mathrm{H}_{2} \uparrow\)

Properties of Aluminium Sulphate

1. Aluminium sulphate is a white crystalline solid. It is readily soluble in water, but it is insoluble in ethanol. 
2. Aluminium sulphate combines with the univalent metal sulphates to form hydrated double sulphates which are commonly known as alum.
3. The decomposition of aluminium sulphate gives the oxides of sulphur which are toxic in nature.

Uses of Aluminium Sulphate

1. Aluminium sulphate is used in water purification system.
2. It is used as a mordant in printing and dyeing.
3. It is used in gardening for balancing the pH of the soil. 
4. Aluminium sulphate is used in sewage treatment.
5. Aluminium sulphate can be used for making paper.
6. It is used in the field of construction as a water proofing agent.

Aluminium Chloride Formula

Aluminium chloride is an inorganic compound with the chemical formula \(\mathrm{AlCl}_{3}\). It is also called as aluminium trichloride. It is a compound containing aluminium and chlorine. Let us discuss more about aluminium chloride in detail.

Aluminium Chloride (AlCl₃)

Aluminium chloride contains three chlorine atoms and one aluminium atom in it. There exists an ionic bond (with a high degree of covalent character) between the aluminium and chlorine atoms. Aluminium chloride can be represented as,

The structure of aluminium chloride can vary. This is because it forms different structures at varying temperatures. For example, aluminium chloride exists as a dimer, \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\) in liquid or molten state. This is done by the donation of electrons by chlorine atoms to aluminium atoms to complete the octet of aluminium atoms. The structure of its dimer can be given as,

Preparation of Aluminium Chloride

Aluminium chloride can be prepared on a large scale by the reaction of aluminium and chlorine. That is,

\(2 \mathrm{Al}+3 \mathrm{Cl}_{2} \rightarrow 2 \mathrm{AlCl}_{3}\)

The above reaction is highly exothermic in nature.

Aluminium chloride can also be prepared on a large scale by the action of dilute hydrochloric acid on the aluminium metal. That is,

\(2 \mathrm{Al}+6 \mathrm{HCl} \rightarrow 2 \mathrm{AlCl}_{3}+3 \mathrm{H}_{2}\)

The temperature range used for the above two reactions is \(650\) to \(750^{\circ} \mathrm{C}\).

Aluminium chloride is also obtained when copper chloride reacts with aluminium metal. That is,

\(2 \mathrm{Al}+3 \mathrm{CuCl}_{2} \rightarrow 2 \mathrm{AlCl}_{3}+3 \mathrm{Cu}\)

This is an example of a single displacement reaction.

Properties of Aluminium Chloride

1. Aluminium chloride appears as a white solid. It sometimes appears as yellow due to the presence of contaminants like iron (III) chloride.
2. It has very low boiling and melting point.
3. Aluminium acts as a Lewis acid. This is because, it can accept lone pair of electrons.
4. Aluminium chloride is hygroscopic in nature. Therefore, it will react vigorously with water. For instance, anhydrous aluminium chloride is partially hydrolysed with the moisture present in the atmosphere to give \(\text {HCl}\) gas.

Uses of Aluminium Chloride

Aluminium chloride has got many uses. They are:

1. Aluminium chloride is mainly used as a catalyst in Friedel-Craft’s reaction.
2. Aluminium chloride is used as a catalyst in organometallic synthesis too.
3. It is used for the manufacture of lubricants, rubber, wood preservatives, etc.
4. It is used in pharmaceuticals and pesticides
5. In aluminium melting, it is used as a flux.

Aluminium Hydrogen Sulphate Formula

Aluminium hydrogen sulphate is a chemical compound with the formula \(\mathrm{Al}\left(\mathrm{HSO}_{4}\right)_{3}\). In this compound, there are; one atom of aluminium, three atoms of hydrogen, three atoms of sulfur and twelve atoms of oxygen. Let us discuss more about aluminium hydrogen sulphate.

Aluminium Hydrogen Sulphate (Al(HSO₄)₃

Aluminium hydrogen sulphate can be represented as,

Properties of Aluminium Hydrogen Sulphate

1. It appears as a solid.
2. The molar mass of aluminium hydrogen sulphate is approximately equal to \(318.2 \mathrm{~g} / \mathrm{mol}\)

Uses of Aluminium Hydrogen Sulphate

1. It is used as an efficient catalyst for the preparation of thioacetals.
2. It can be used as a solvent.
3. It is used as an efficient reagent in organic chemistry.

Aluminium Phosphate Formula

Aluminium phosphate is a compound with the chemical formula \(\mathrm{AIPO}_{4}\). It is also known as aluminium monophosphate. Aluminium phosphate naturally occurs as berlinite. Let us discuss more about aluminium phosphate.

Aluminium Phosphate (AlPO₄)

Aluminium phosphate is an ionic compound. That is, it contains aluminium \(\left(\mathrm{Al}^{3+}\right)\) cation and phosphate \(\left(\mathrm{PO}_{4}^{3-}\right)\) anion. Aluminium phosphate can be represented as,

Preparation of Aluminium Phosphate

Aluminium phosphate can be prepared from its naturally occurring minerals such as berlinite, variscite and meta-variscite. The other chemical methods used for the preparation of aluminium phosphate are not known or studied in detail.

Properties of Aluminium Phosphate

1. Aluminium phosphate is a white crystalline powder. 
2. Its melting point is equal to \(1800^{\circ} \mathrm{C}\). Beyond this temperature, it decomposes.
3. It is insoluble in water and slightly soluble in nitric acid and hydrochloric acid.
4. It exhibits chirality and piezoelectric properties.

Uses of Aluminium Phosphate

1. Aluminium phosphate is majorly used in electrical industries due to its piezoelectric properties.
2. It is used for the production of adhesives and rubber.
3. It is the most common antacid used.
4. It is used in dental cement, cosmetics, ceramics, paints, pharmaceuticals, papers, etc.

Aluminium Chloride Hexahydrate Formula

Aluminium chloride hexahydrate is a compound with the chemical formula \(\mathrm{AlCl}_{3} \cdot 6 \mathrm{H}_{2} \mathrm{O}\). It is also known as aluminium trichloride hexahydrate. It is the hexahydrated form of aluminium chloride. Let us discuss more aluminium chloride hexahydrate. 

Aluminium Chloride Hexahydrate (AlCl₃· 6H₂O)

Aluminium chloride hexahydrate consists of \(\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right){6}\right]^{3+}\) centers and chloride counterions. The cations and anions in this compound is joined together by hydrogen bonds. Aluminium chloride hexahydrate can be represented as,

Properties of Aluminium Chloride Hexahydrate

1. Aluminium chloride hexahydrate appears as a white powder.
2. It is a stable form, but it will decompose upon exposure to moist air or water.
3. It is incompatible with acids.

Uses of Aluminium Chloride Hexahydrate 

1. Aluminium chloride hexahydrate tropical is used to treat excessive sweating on the skin.
2. It is used as a catalyst in Friedel-Crafts alkylation and other related reactions.

Aluminium Cyanide Formula

Aluminium cyanide is a chemical compound with the formula \(\mathrm{Al}(\mathrm{CN})_{3}\). It is an example of a metallic cyanide. It is also known as aluminium tricyanide. Let us discuss more about aluminium cyanide. 

Aluminium Cyanide Al(CN)₃

Aluminium cyanide contains one aluminium atom, three nitrogen and carbon atoms. It is an ionic compound. Aluminium cyanide can be represented as,

The molar mass of aluminium cyanide is approximately equal to \(105.036 \mathrm{~g} / \mathrm{mol}\).

Aluminium cyanate can be produced as an ammoniate by the reaction of the metal aluminium with mercuric cyanide in liquid ammonia. 

Aluminium cyanide, on exposure to water, aluminium hydroxide is formed.

Summary

Aluminium is a group \(13\) element with the chemical symbol \(\text {Al}\). It belongs to group \(13\) and period \(3\) of the periodic table. In this article, we have learnt about the metal aluminium in detail. The Aluminium symbol, occurrence, preparation, physical and chemical properties and its uses. Aluminium combines with different elements to form a large number of compounds. Some of such compounds are also included in this article.

FAQs on Aluminium Formula

Q.1. What is the chemical formula of aluminium oxide?
Ans: Aluminium oxide is a chemical compound with the formula \(\mathrm{Al}_{2} \mathrm{O}_{3}\). Aluminium reacts with oxygen to form this compound.

Q.2. What is the formula for aluminium nitrite?
Ans: The chemical formula of aluminium nitrite is \(\mathrm{Al}\left(\mathrm{NO}_{2}\right)_{3}\). It is an ionic compound.

Q.3. What is the formula for aluminium sulphate?
Ans: The chemical formula of aluminium sulphate is \(\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\). Aluminium reacts with dilute sulphuric acid to form aluminium sulphate.

Q.4. What is the formula for aluminium nitrate?
Ans: The chemical formula of aluminium nitrate is \(\mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}\). It is formed by the reaction of aluminium with dilute nitric acid.

Q.5. What is the formula of aluminium hydrogen sulphate?
Ans: Aluminium hydrogen sulphate is a chemical compound with the formula \(\mathrm{Al}\left(\mathrm{HSO}_{4}\right)_{3}\).

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