Chemical properties of ALUMINIUM?

Hey..Cassie....

I am taking my AS-Levels this year, so, I hope my answer help you a bit....


Firstly, you got to know about the :

Basic Information

Name: Aluminum
Symbol: Al
Atomic Number: 13
Atomic Mass: 26.981539 amu
Melting Point: 660.37 °C (933.52 K, 1220.666 °F)
Boiling Point: 2467.0 °C (2740.15 K, 4472.6 °F)
Number of Protons/Electrons: 13
Number of Neutrons: 14
Classification: Other Metals
Crystal Structure: Cubic
Density @ 293 K: 2.702 g/cm3
Color: Silver
British Spelling: Aluminium
IUPAC Spelling: Aluminium

Properties of Aluminium
Aluminium has the chemical symbol Al, atomic number 13, and atomic weight 26.98. The isotope with mass number 27 is the only stable isotope. It is a soft, light, gray metal that resists corrosion when pure in spite of its chemical activity because of a thin surface layer of oxide. It is nonmagnetic and nonsparking. Its density is 2.6989 g/cm3, melting point 669.7°C and boiling point 1800°C. Its electrical resistivity is 2.824 μΩ-cm at 20°C, with temperature coefficient 0.0039°C-1, the same as copper's. Its thermal conductivity is 2.37 W/cm-K at 300K, and the linear coefficient of expansion is 23.86 x 10-6°C-1. The specific heat is 0.2259 cal/g-K, and the heat of fusion is 93 cal/g. The first ionization potential is 5.96V, second 18.74V and third 28.31V. Its electrode potential is 1.67V positive with respect to hydrogen. When near its melting point, it becomes "hot short" and crumbles easily. As a pure metal, it is quite soft, and must be strengthened by alloying with Cu, Mg, Si or Mn before it can be used structurally. Aluminium bronze is 90 Cu, 10 Al, a strong, golden-yellow alloy with excellent physical properties. The Young's modulus of pure aluminium is 10 x 106 psi, the shear modulus 3.8 x 106 psi, Poisson's ratio 0.33, and the ultimate tensile strength 10,000 psi, with 60% elongation. Pure aluminium is very ductile and malleable, and unsuitable as a structural material. Its hardness is 15 Brinell (500 kg, 10 mm). The useful wrought alloys contain 1-7% magnesium and 1% manganese. Its crystal form is face-centered cubic, with lattice constant a = 0.404 nm, and nearest-neighbor spacing of 0.286 nm.

The familiar strong aluminium alloy Duralumin should really be Düralumin, since it was originally the product of the Dürener Metallwerke in Germany. Düren is about halfway between Köln and Aachen in northwestern Germany. Dr Alfred Wilm was testing aluminium alloys there about 1909, and was surprised that an alloy 96 Al, 3.5 Cu, 0.5 Mg, which was not too impressive on a first test, strengthened greatly with a few day's rest after casting. What was happening was that all the Cu was in solution at 500°C, but at room temperature the solid could hold only 0.5% in solid solution. The hard intermetallic CuAl2 was forming slowly, making hard bits that would hinder the propagation of slip dislocations. This "age hardening" was the start of the general process of precipitation hardening that has been very important in strong alloys. The alloy was used in Zeppelins, and now is a major component of most aircraft, in the form of Alclad, in which the Duralumin is given a sheathing of pure aluminium to make it corrosion-resistant.

Liquid aluminium easily absorbs gases from the air, and these gases are expelled on solidification, causing flaws in castings. Casting alloys include silicon, and perhaps a little copper or nickel to help to avoid this. A eutectic is formed with aluminium at 11% silicon. Also, large crystals may be a problem if the aluminium is poured while too hot. The shrinkage on solidification is 0.2031 inches per foot for pure aluminium, 0.156 inches per foot for casting alloys.

Chemistry of Aluminium
The electron configuration of aluminium is 1s22s22p63s23p. The outer three electrons occupy three s2p hybrid orbitals that point in orthogonal directions. These electrons easily form covalent bonds, as in anhydrous AlCl3. This compound easily sublimates, showing that it is not ionic, and is partially hydrolyzed by water to release HCl gas. It cannot be formed by heating the hydrated form to drive off water. This only produces the oxide and HCl gas. It is now made commercially by heating aluminum oxide with carbon and chlorine. It is used in the refining of motor oil, and as a catalyst. Hydrated aluminium chloride is used as a personal deodorant. The acid environment it creates is unpleasant for microbes and mild enough to be non-irritating.

The spectroscopic ground state is 3s23p2 3P. The resonance line is at 396.15 nm, so the aluminium atom is not excited in the flame, and gives it no color. When the atom is excited, most of the lines are in the red or infrared. Aluminium is in column IIIA of the periodic table, which includes boron, aluminium, gallium, indium and thallium. Aluminium is the only common element in the group, and is considerably different from the others in physical and chemical properties. Boron is an acidic nonmetal, while gallium, indium and thallium are typical basic metals.

Aluminium should displace hydrogen from water because of its positive oxidation potential, but does not normally do so because of the protection by a surface layer of oxide. This oxide has the same density as the metallic aluminium, so it does not crack or wrinkle when it is formed, a lucky thing. A little HCl or NaOH that dissolves the oxide will permit the evolution of hydrogen. Aluminium pots and pans should not be used with acidic or strongly alkaline foods, that will dissolve the protective layer and allow the metal to be attacked. Aluminium is attacked by hydrochloric acid, but not by oxidizing acids like nitric. Aluminium tank cars are even used to transport nitric acid. If aluminium is amalgamated with mercury, the protective oxide layer is removed, the metal becomes very reactive, and will displace hydrogen from water. It can be used for handling cold nitric acid, but dissolves readily in alkalis to form aluminates, an example of the amphoteric behavior of aluminium. Formation of the oxide also prevents aluminium from being soldered with ordinary Sn-Pb solder, since the solder will not wet it. Sn-Zn solders can be used with aluminium. A suitable alloy is 85 Sn, 15 Zn, 5 Al. 60 Zn, 40 Cd has better corrosion resistance, but is harder to melt. The solder itself serves as a flux. With a suitable flux to protect the metal, aluminium can be welded.

Aluminium was first isolated by Hans Christian Oersted (1777-1851) in 1824 by reducing it from its oxide with potassium amalgam. The reaction is AlCl3 + 3K → 3KCl + Al. Two years later, Wöhler made the metal the same way. For some reason, Wöhler is usually considered the discoverer and got most of the fame. This Oersted is the same who discovered the magnetic effect of the electric current in 1820. In the Dictionary of Scientific Biography, the article on Oersted does not mention his work with aluminium. Refractory oxides such as alumina, silica or magnesia, were considered elements earlier, when all attempts to decompose them had failed. Only electrolysis made the decomposition possible, either directly or through the production of reactive metals like sodium and potassium.

The thermite reaction, discovered by Goldschmidt, is also a displacement reaction, but here aluminium reduces iron. The reaction is Fe2O3 + 2Al → 2Fe + Al2O3, which liberates a good deal of heat. The liquid metal produced is at about 2300°C, which is very hot. Powdered aluminium and rust in the approximate ratio of 1:3 are packed in a refractory crucible with a magnesium ribbon, or a powder of magnesium and barium peroxide, to ignite it. Either the red or black iron oxide can be used, giving "red Thermit" or "black Thermit." A trade name for the powder is Thermit. The vigorous reaction makes liquid iron or steel, which flows out of a hole in the bottom of the crucible into the mold and can be used for welding. The stock to be welded is usually preheated with a gas flame playing through the mold. The metal produced is about half the weight of the original mixture. This reaction is also called aluminothermic, and can be used for reduction of other metals, such as nickel, manganese or chromium.

Alumina, Al2O3, is the refractory oxide of aluminium, which does not melt below 2000°C. Corundum is the natural form of alumina, a very hard (9 on the Mohs scale, just below diamond) and heavy (4.02 g/cm3) that is a valuable gem when transparent. A chromium impurity makes ruby, while iron, cobalt or titanium makes sapphire. Fused alumina is called alundum, and is an artificial substitute for corundum, especially as an abrasive. Artificial rubies and sapphires of high quality are rather easily made. Artificial ruby is used in the ruby laser. The colors are not due to aluminium, but to the isolated impurity atoms. Emery is a natural corundum substance with magnetite or hematite as an impurity, which turns it black. Emery is an excellent abrasive, but should not be used where its electrical conductivity or magnetic impurities are deleterious. At 1700°C, alumina crystals become plastic and can be bent into any desired shape, for things like thread guides and phonograph needles.

Aluminium can be protected by a thick layer of oxide made by electrolysis, a process called "anodizing." The surface is first thoroughly cleaned and degreased in trichloroethylene, or by electrolysis, where the aluminium is the cathode and the grease driven off by the evolved hydrogen. Then the metal is made the anode in a bath of dilute sulphuric acid, and electrolyzed at 100 A/m2 and cell voltage 15V for about thirty minutes. The evolved oxygen combines with the aluminium to form a layer .007 to .015 mm thick (the normal oxide thickness formed in air is 13 nm). The layer is porous, and can be dyed by dipping in dye solutions. Finally, it is "sealed" by boiling in water, perhaps after dipping in a 1% nickel acetate solution or a surface application of linseed oil or similar. This renders the surface impermeable and resistant to staining.

Closely related to alumina is the hydroxide, Al(OH)3, usually formed as a gelatinous precipitate when aluminum compounds are hydrolyzed in water. If water is driven out of this precipitate by heating, a light, foamy solid results called activated alumina that will absorb moisture and other things, and can be reactivated by heating. This hydroxide reacts with both acids and bases according to the formula H+ + AlO2- + H2O = Al(OH)3 = Al+++ + 3OH-. Adding an acid removes OH-, driving the reaction to the right, while adding a base removes H+, driving the reaction to the left. Since it can go either way, aluminum hydroxide is called amphoteric, and is an excellent example of the type.

If we consider other hydroxides of elements in the same row of the periodic table, we see that NaOH is a base, and can react only with acids, while P(OH)5 = H+ + H2(PO)4- + H2O is an acid, and reacts only with bases. Only the first stage of ionization is shown. Aluminium is halfway between these two. This behavior depends on the ionic charge and the ionic radius, as is explained in any text on inorganic chemistry.

Aluminium sulphate, Al2(SO4)3·18H2O is a very useful aluminum compound, made from the oxide and sulphuric acid. When moistened, it becomes acidic because of hydrolysis, as just described. It is also called pickle alum from its use in giving sourness to pickles. The acidity can be used to produce carbon dioxide if combined with sodium bicarbonate, as in baking soda bread. Hydrolysis gives the gelatinous hydroxide, which is useful as a dye mordant, as a flocculent filter, and as size for paper. Dyes adhere very poorly to cotton, for example, so to dye cotton it is soaked in aluminium sulphate solution. The hydroxide impregnates the fibres and clings tightly to them. A dye then is adsorbed by the hydroxide, forming a lake. The word "lake" is from "lac," an insect resin originally used in lacquer which also had the property of absorbing dyes and becoming brightly colored.

Aluminium sulphate is found in nature as the rare mineral Kalinite, which is soluble in water, so it is found only near volcanoes and such places where it is make by the action of sulphuric acid on clays, such as on Lipari, near Vesuvius, and a few places in Germany and South America. Alum, KAl(SO4)2·12H2O (or twice this) is not as scarce, but is still rare, found in Europe and Utah. This mineral is partly hydrated, crystallizes in the hexagonal system, and is insoluble. It dissolves in H2SO4, however. Before 1600, when strong acids were not available, alum could be made by roasting this mineral and then extracting with water.

In general, an alum is of the form M+M'+++(SO4)2·12H2O. The monovalent cation can be K, Na, Cs, Rb, NH4 or Tl, while the trivalent cation can be Al, Fe or Cr. All form characteristic octahedral crystals (the symmetry may actually be monoclinic, as in KAl alum, but is not far from cubic). Alums are astringent, or styptic, and check bleeding, aiding those with exceptionally sharp or exceptionally dull razors. Aluminium acetate is a very soluble compound of aluminium, and behaves like the sulphate in the presence of water, precipiatating the hydroxide. Alums are much more soluble in hot water than in cold, so that crystals are easily grown from a solution that has become supersaturated by cooling. In cool water, KAl alum is less soluble than KFe, so it is very easy to eliminate small amounts of Fe ion by fractional crystallization. This ability to get very pure alum is very useful in dyeing, where a little Fe ion spoils the colour.

Alums are used with sodium bicarbonate in fire exinguishers as well as in baking powder, and for the same reason, the production of CO2. Cloth soaked in alum is fire-resistant, but I have not yet been able to discover why this should be so. Alum has also been mentioned as a fire retardant for wood, but again I do not know why (yet). These uses were probably unknown in ancient times, when alum was rare and expensive, used only as a styptic and in medicines, and perhaps rarely as a mordant. The famous mention of alum in Herodotus is probably not alum, as I maintain in another page on this site. Egypt had no alum deposits, and had no way to make the substance. Also, a shipload of this rather rare substance would be astonishing. The rebuilders of the Delphic temple would be at a loss over what to do with it.

Aluminium is not a very colorful element. It gives no coloration to the flame, and its compounds are relentlessly white. For a long time, the usual test for it consisted of forming Thénard's Blue, cobalt aluminate. Other ions interfere with this test (also giving blue) so the modern alternative of using Aluminon, a red dye, is now preferred. Aluminon is ammonium aurin tricarboxylate, whose structure is shown in the diagram. The chromophore is the region of alternating single and double bonds in the center. This dye will not adsorb on hydroxides of chromium, zinc, lead, tin or antimony to form a lake, having a decided preference for aluminium hydroxide. Aluminium dissolves slowly in dilute hydrochloric acid to make a clear solution. When ammonium hydroxide is added, a characteristic translucent gel precipitates, with a bluish tinge. Since aluminium is amphoteric, this gel will dissove in an excess of alkali. Other amphoteric cations can make a similar precipitate, so a test is necessary to confirm that aluminium is present. If a little aluminon is added, it makes a bright red lake with the gelatinous hydroxide, confirming the presence of aluminium.

Lapis lazuli, the mineral lazurite, is Na4-5Al3(SiO4)3S. This beautiful dark blue stone was greatly prized in antiquity, and is one aluminium compound that is not white. The best comes from northeastern Afghanistan. Finely ground, it made the pigment ultramarine. Ultramarine is now artificially made by fusing clay, carbon and sodium sulphate. Also not white is turquoise, Al2(OH)3PO4·H2O. These two stones are beautiful enough to compensate for all the white powders. Garnet and jade (jadeite, not nephrite) also contain some aluminium.

Aluminium salts are not poisonous, even when soluble.

Pure aluminium is a silvery-white metal with many desirable characteristics. It is light, nontoxic (as the metal), nonmagnetic and nonsparking.



It is decorative. It is easily formed, machined, and cast. Alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties.

Strength depends on purity. 99.996 per cent pure aluminium has a tensile strength of about 49 megapascals (MPa), rising to 700 MPa following alloying and suitable heat treatment.

Although not found free in nature, Aluminium is an abundant element in the earth's crust.

A key property is low density. Aluminium is only one-third the weight of steel.

Aluminium and most of its alloys are highly resistant to most forms of corrosion. The metal's natural coating of aluminium oxide provides a highly effective barrier to the ravages of air, temperature, moisture and chemical attack.

Aluminium is a superb conductor of electricity. This property allied with other intrinsic qualities has ensured the replacement of copper by aluminium in many situations.

Aluminium is non-magnetic and non-combustible, properties invaluable in advanced industries such as electronics or in offshore structures.

Aluminium is non-toxic and impervious, qualities that have established its use in the food and packaging industries since the earliest times.

Other valuable properties include high reflectivity, heat barrier properties and heat conduction. The metal is malleable and easily worked by the common manufacturing and shaping processes.

Physical Properties Density / Specific Gravity (g.cm-3 at 20 °C) 2.70
Melting Point (°C) 660
Specific heat at 100 °C, cal.g-1K-1 (Jkg-1K-1) 0.2241 (938)
Latent heat of fusion, cal.g-1 (kJ.kg-1) 94.7 (397.0)
Electrical conductivity at 20°C
(% of international annealed copper standard) 64.94
Thermal conductivity (cal.sec-1cm-1K-1) 0.5
Thermal emmisivity at 100°F (%) 3.0
Reflectivity for light, tungsten filament (%) 90.0

These properties can be very significantly altered with the addition of small amounts of alloying materials. Aluminium reacts with oxygen to form a microscopic (0.000000635cm) protective film of oxide, which prevents corrosion.

Aluminium in massive form is non-flammable. Finely divided particles will burn. Carbon monoxide or dioxide, aluminum oxide and water will be emitted. This is a useful property for making rocket fuel.

These are some facts you must know,too....

Facts

Date of Discovery: 1825
Discoverer: Hans Christian Oersted
Name Origin: From the Latin word alumen
Uses: airplanes, soda cans
Obtained From: bauxite

Okay...

I hope this helps you.....

1

Al(OH)2 Called Boehmite. Mole. Wt. 59.99, density-3.01 melts at 300 C.;insoluble in hot or cold water;white;microscopic orthorhombic shape, or am I confusing this w/ AlO(OH) naturally occurring diaspora ?

Bet you did not know that Al powder is explosive when mixed with air and ignited.
Really interesting compounds are aluminum alkyls such as triethyl Al. They ignite on exposure to air and explode violently when in contact with water.

Al is amphoteric. Look up the word.

Al:

It is a metal thus is malleable, good conductor of heat and electricity etc...

It is a potent Lewis Acid (accepts an electron pair in a co-ordinate bond) and is often found as [Al(H2O)6]3+

It can also form the dimer Al2Cl6

For a metal it has a low density.

Its hydroxide is amphoteric:
[Al(H2O)3(OH)3] + H+ ------> [Al(H2O)4(OH)2]+
[Al(OH)3] + OH- -----> [Al(OH4)]-

1. they accept electrons more easily so they are reactive
2. It reacts moderately with water
3. IT is however not really reactive, not as reactive as sodium, coz it has an oxide layer which protects it from further attack or reaction.

that's all i can find

aluminium is a metal... it has a valency of 3.. it has got all the props that a metal has for eg : lusturous, good conductor of heat and electricity..etc etc.... it is highly electropositive metal. it has emptyd orbitals and thus can borrow electrons and attain a stable confugeration... as its compounds are elctron deficient..! its compounds such as AlCl3 etc act as a lewis acid..the hybridisation state of Al is sp3d2...
aluminium forms a thin protective oxide layer which prevents its further corrossion.. and this is also the reason y they do not react with weak acids.. Al is amphoteric(it reacts with acids as well as base) Al reacts with halogen to form trihalides... Al's covalency can be expected beyond 4 due to the presence of empty d orbitals...

Here is a little about aluminium for you.

Aluminium is made of...aluminium (Al) and basically, it is other elements added to it that makes it a 'grade' of aluminium. There are over 100 different grades of aluminium.

You can get pure aluminium, down to grades with small compositions of aluminium. To be called 'aluminium' in it's truest form, aluminium has to be the highest chemical element in that grade.

To be very specific and to be able to tell you the full properties of Aluminium, you would need to give a GRADE. This will be something like Grade 5082, or Grade 1050A. THEN you can find out the full chemical properties of the other elements in the grade.

Pure aluminium is a silvery-white metal with many desirable characteristics. It is light, nontoxic (as the metal), nonmagnetic and nonsparking and is therefore used a lot in aircraft.

It is decorative. It is easily formed, machined, and cast. Alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties.

Strength depends on purity. 99.996 per cent pure aluminium has a tensile strength of about 49 megapascals (MPa), rising to 700 MPa following alloying and suitable heat treatment.

Although not found free in nature, Aluminium is an abundant element in the earth's crust.

A key property is low density. Aluminium is only one-third the weight of steel.

Aluminium and most of its alloys are highly resistant to most forms of corrosion. The metal's natural coating of aluminium oxide provides a highly effective barrier to the ravages of air, temperature, moisture and chemical attack.

Aluminium is a superb conductor of electricity. This property allied with other intrinsic qualities has ensured the replacement of copper by aluminium in many situations.

Aluminium is non-magnetic and non-combustible, properties invaluable in advanced industries such as electronics or in offshore structures.

Aluminium is non-toxic and impervious, qualities that have established its use in the food and packaging industries since the earliest times.

Other valuable properties include high reflectivity, heat barrier properties and heat conduction. The metal is malleable and easily worked by the common manufacturing and shaping processes.

These properties can be very significantly altered with the addition of small amounts of alloying materials. Aluminium reacts with oxygen to form a microscopic (0.000000635cm) protective film of oxide, which prevents corrosion.

Aluminium in massive form is non-flammable. Finely divided particles will burn. Carbon monoxide or dioxide, aluminum oxide and water will be emitted. This is a useful property for making rocket fuel.

There is an aluminium organisation that evolved to extol the virtues of aluminium and lots of information is available on sites such as www.lme.com or www.matweb.com.

info on
http://www.lenntech.com/Periodic-chart-elements/Al-en.htm

melting point -660.4 °C
boiling point-2467 °C
density-2.7 g.cm -3 at 20 °C
standard potential- - 1.67 V
1. Valence : Since Al has 3 electrons in its M-shell, it gives them off easily. Al therefore has valence = 3+ .
2. Action of air : Al is a reactive metal and it reacts with air. When Al is exposed to air, it reacts with oxygen to form a thin layer of Al2O3. This acts as a protective layer and stops further corrosion of Al. Al2O3 is unreactive and rest of the Al remains unattacked by air. The reaction is exothermic.
3. Action of water : Al reacts with water to form a hydroxide. The surface layer of pure Al forms the aluminium hydroxide, which acts like a protective layer for the rest of the Al. Hydrogen gas is emitted in this reaction.
4 Reaction with acids : Al reacts with HCl to form Al-chloride and releases hydrogen.
5Action of alkalis : Al reacts with NaOH and KOH to form sodium and potassium aluminate, releasing hydrogen.
6. Reaction with chlorine : Aluminium chloride is formed when Al is heated in chlorine atmosphere. The reaction is shown below.
7. Reducing action : Al strongly attracts oxygen. Hence it is a good reducing agent. The example given below shows how Al reduces Fe (III) oxide. This is an exothermic reaction and the temperature of the reaction goes up to as much as 3500°C.
8. Test for aluminium : If Al is present in ionic form or salt form in a solution, it can be tested by pouring ammonium hydroxide. A white precipitate of aluminium hydroxide separates out and ammonium chloride solution remains behind. This is a practical test for the presence of Al.

thats one heck of an answer what more can you say