Aluminum (Al) or alumium, chemical element, silvery-white metal of Group 13 of periodic table uses widely due to its exclusive properties and cheap in price

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Aluminum
Aluminum in Periodic Table
Aluminum (Al) or alumium, chemical element, silvery-white, lustrous, low melting,
soft metal of Group 13 (IIIA) or boron family of the periodic table uses widely in our
everyday life. Aluminum is the most abundant metallic element in the earth’s crust (8
percent by weight) and the third most abundant chemical element after oxygen and
silicon. Aluminum differs from the first member of Group 13 (boron) due to its
chemical properties, high reactivity, and cationic chemistry in an aqueous solution. It
combines most of the nonmetallic elements like nitrogen, sulfur, halogens, and
intermetallic aluminum compounds with a large number of metals.
The face-centered cubic crystal lattice (fcc), aluminum has the chemical symbol Al,
atomic number 13, atomic weight 26.928, melting point 660 °C, boiling point 2467
°C, density 2.70 gm/cm , and electron configuration 1s 2s 2p 3s . The name
aluminum coming from the Latin word alumen, which describe the aluminum
potassium sulfate, KAl(SO ) , 12H O. The common oxidation number or states of
metal +1. +2 and +3. Due to decreases of lattice energy with increasing size of cation
3 2 2 6 3
4 2 2

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size, it should be likely to form an Al ion. Due to large ionization energy not
compensated by weak lattice energy, aluminum commonly attains +3 state by
covalent bonding.
Abundance and Occurrence
The most abundant element, aluminum found in various silicates minerals like mica,
feldspar, kaolinite, and clay. The only fluoride mineral is cryolite (Na AlF ), found in
Greenland. The most important minerals found in nature as oxide and anhydrous
hydrated oxides. The oxide like Corundum (Al O ) used in Gems (ruby, sapphire) due
to its hardness. The chief commercial source of metallic aluminum is hydroxo oxide
like Al O , xH O, or bauxite. A workable bauxite sample contains 40 to 60 percent
metal aluminum oxide (Al O ), 12 to 30 percent water, 1 to 15 percent iron oxide
(Fe O ), and 3 to 4 percent titanium oxide (TiO ). Rich deposits of bauxite are found
in Australia, Brazil, Guinea, Jamaica, France, United States, Russia, India, and
several African counties.
+3
3 6
2 3
2 3 2
2 3
2 3 2

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History and Production
Alum was the compound of aluminum widely used in Rome for the production of
different types of medicine and dyes in textile. British chemist Sir Humphry Davy
failed to isolate the metal but suggested the name of the element aluminum or
alumium. In 1825 Denmark physicist Hans Christian Orsted first isolate the metal by
reducing aluminum chloride (AlCl ) with potassium amalgam. Commercial
production of the element started in 1954 by electrolysis of NaAlCl .
Aluminum can be extracted electrolytically from bauxite by electrochemical cells.
Purified bauxite (melting point 2050 °C) is dissolved in cryolite and electrolyzed at
950 °C in carbon lined steel cells. A mixture of cryolite, CaF , AlF , Al O , Li CO in
electrolyte used because it has a lower melting point, permits larger current flow,
reduces fluorine emission. The electrode reaction for the production of aluminum,
cathode: 2Al + 6e → 2Al and anode: 3O → 3O + 6e. The molten aluminum sinks
to the bottom of the cell and drained out. The surface of the electrolyte covered with a
layer of coke, which oxidized evolving oxygen for the protection of valuable
electrodes.
Properties and Chemistry
Aluminum is not attacked by water owing to the presence of a protective coating. If
the film is removed by amalgamation, water form [Al(OH) + H ]. All the elements of
3
4
2 3 2 3 2 3
+3 -2
3 2

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Group 13 have different chemical properties and reactivity. For example, Al, Ga, In
dissolve in aqueous HCl giving M ions but Tl does not due to the instability of TlCl.
Al scarcely attacked by dilute sulfuric acid but concentrated acid is reduced to sulfur
dioxide. Dilute and concentrated nitric acid render aluminum passive by forming a
protective oxide layer. Al dissolves in hot aqueous alkali (lithium, sodium, and
potassium) to form [Al(OH) ] and hydrogen.
Compounds
The electronic structure of aluminum suggested that it forms mostly trivalent
chemical compounds. The aluminum compounds in the +3 state are dominantly by
covalent chemical bonding but in suitable conditions, it formed +2 and +1
compounds like AlCl, Al2O, AlO. In learning chemistry, the tripositive ion (Al ) ions
may be stabilized in aqueous solutions through strong hydration energy, usually, six
water molecules held strongly by the Al ion. The hydride of Al is a colorless
involatile solid, thermally unstable above 150-200 °C. It is a strong reducing agent
and adducts with strong Lewis bases. The Tetrahydro complex of Al like LiAlH is a
very important chemical compound widely uses in organic chemistry or reduction of
hydrocarbon.
All the four trihalides of aluminum have the general formula AlX , where X =
fluorine, chlorine, bromine, and iodine. All the compounds may be prepared by direct
combination of the metal with halides. The properties of the trihalides very widely.
For example, fluoride is an ionic crystalline solid. Alumina is an important chemical
compound of aluminum with two structural forms like α-Al O and ϒ-Al O . The α-
Al O occurs in nature as corundum which is resistant to water and acids and uses in
Gems. The γ-alumina is distorted, less dense, soft with high surface tension in the
liquid form. These qualities of γ-alumina an excellent reagent for dehydration,
decolorization, and absorption chronograph. β-alumina is now being developed as a
ceramic ion conductor useful for high energy batteries. Large quantities of alumina
used for the commercial production of aluminum.
+3
4
–
+3
+3
4
3
2 3 2 3
2 3

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Uses of Aluminum
In recent years aluminum acquired a high position among the metals due to its
several exclusive properties, it is cheap in price, easily malleable, non-toxic, and fairly
corrosion resistant in dry conditions, good thermal and electrical conductors. The
corrosion-resistant properties due to the protective oxide layer in metal. Pure
aluminum is quite soft and weak but the commercial form contains small amounts of
silicon and carbon is hard and strong. The mechanical strength of aluminum
significantly increases by alloying with metals like iron, copper, manganese, silicon,
magnesium, or zinc. The aluminum alloys are uses in construction work,
transportation, containers and packaging, electrical power lines, machinery, and the
paint industry.
The metal and its alloys are now extensively used in aircraft, in rocket fuels, trucks,
trailers, and car frames, in making windows, doors, building panels, in making
machinery, utensils, and other household products including furniture also made of
aluminum alloy.