ALUMINIO

Introducción

Número atómico: 13
Grupo: 13 or III A
Peso atomico: 26.981538
Período: 3
Número CAS: 7429-90-5

Clasificación

chalcogen
halógeno
Gas noble
Lantanoides
Actinoides
Elemento de tierras raras
Platino Metal Group
transuranium
No hay isótopos estables
Sólido
Líquido
Gas
Sólido (Predicho)

Descripción • Usos / Función

The ancient Greeks and Romans used alum in medicine as an astringent, and as a mordant in dyeing. In 1761 de Morveau proposed the name alumine for the base in alum, and Lavoisier, in 1787, thought this to be the oxide of a still undiscovered metal. Wohler is generally credited with having isolated the metal in 1827, although an impure form was prepared by Oersted two years earlier. In 1807, Davy proposed the name alumium for the metal, undiscovered at that time, and later agreed to change it to aluminum. Shortly thereafter, the name aluminium was adopted to conform with the “ium” ending of most elements, and this spelling is now in use elsewhere in the world. Aluminium was also the accepted spelling in the U.S. until 1925, at which time the American Chemical Society officially decided to use the name aluminum thereafter in their publications. The method of obtaining aluminum metal by the electrolysis of alumina dissolved in cryolite was discovered in 1886 by Hall in the U.S. and at about the same time by Heroult in France. Cryolite, a natural ore found in Greenland, is no longer widely used in commercial production, but has been replaced by an artificial mixture of sodium, aluminum, and calcium fluorides. Bauxite, an impure hydrated oxide ore, is found in large deposits in Jamaica, Australia, Surinam, Guyana, Arkansas, and elsewhere. The Bayer process is most commonly used today to refine bauxite so it can be accommodated in the Hall-Heroult refining process, used to make most aluminum. Aluminum can now be produced from clay, but the process is not economically feasible at present. Aluminum is the most abundant metal to be found in the earth’s crust (8.1%), but is never found free in nature. In addition to the minerals mentioned above, it is found in feldspars, granite, and in many other common minerals. Seventeen isotopes and isomers are known. Natural aluminum is made of one isotope, 27Al. Pure aluminum, a silvery-white metal, possesses many desirable characteristics. It is light, nontoxic, has a pleasing appearance, can easily be formed, machined, or cast, has a high thermal conductivity, and has excellent corrosion resistance. It is nonmagnetic and nonsparking, stands second among metals in the scale of malleability, and sixth in ductility. It is extensively used for kitchen utensils, outside building decoration, and in thousands of industrial applications where a strong, light, easily constructed material is needed. Although its electrical conductivity is only about 60% that of copper, it is used in electrical transmission lines because of its light weight. Pure aluminum is soft and lacks strength, but it can be alloyed with small amounts of copper, magnesium, silicon, manganese, and other elements to impart a variety of useful properties. These alloys are of vital importance in the construction of modern aircraft and rockets. Aluminum, evaporated in a vacuum, forms a highly reflective coating for both visible light and radiant heat. These coatings soon form a thin layer of the protective oxide and do not deteriorate as do silver coatings. They have found application in coatings for telescope mirrors, in making decorative paper, packages, toys, and in many other uses. The compounds of greatest importance are aluminum oxide, the sulfate, and the soluble sulfate with potassium (alum). The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glassmaking and refractories. Synthetic ruby and sapphire have found application in the construction of lasers for producing coherent light. In 1852, the price of aluminum was about $1200/kg, and just before Hall’s discovery in 1886, about $25/kg. The price rapidly dropped to 60¢ and has been as low as 33¢/kg. The price in December 1995 was about $1.70/kg. 1

• "[is] a highly important structural material in a wide variety of applications from aircraft bodies to bicycle components" 2
• "Pure aluminum is soft and weak; moreover, it loses strength rapidly above 300°C. What you recognize as aluminum is actually aluminum alloyed with small amounts of other elements, which strengthen the metal and improves its properties. A large passenger plane may use more than 50 tons of aluminum alloy. A typical alloy may contain about 4% copper with smaller amounts of silicon, magnesium, and manganese. To make a softer, more corrosion-resistant alloy for window frames, furniture, highway signs, and cooking utensils, however only manganese may be included." 3
• "Recycling of aluminum drink cans is now so successful that more than two thirds of this aluminum is used to produce new cans." 4
• "can be readily extruded into wires or rolled, pressed, or cast into shapes. Because of its relatively low density, aluminum is often used as a lightweight structural metal. It is often alloyed with Mg and some Cu and Si to increase its strength. Many buildings are sheathed in aluminum, which resists corrosion by forming an oxide coating...Aluminum is now used in transmission lines and has been used in wiring in homes. The latter use has been implicated as a fire hazard however, due to the heat that can be generated during high current flow at the junction of the aluminum wire and fixtures of other metals...The very negative enthalpy of formation of aluminum oxide makes Al a very strong reducing agent for other metal oxides. The thermite reaction is a spectacular example. It generates enough heat to produce molten iron for making steel." 5
• "Aluminum was so cherished by royalty in the early to mid-1800s that they alone ate with aluminum spoons and forks while their lower-class guests dined with cheaper gold and silver service." 6
• "The metal finds use in vehicles, aircraft, packaging, cookware, construction materials, etc." 7
• "Most of the aluminum objects we see are not aluminum alone, as other metals are added to harden it. For example, the ordinary aluminum cooking utensil contains 98.8% aluminum; 1.2% manganese. Aluminum is excellent for such utensils because it conducts heat well, is light, durable, does not chip or rust, and is harmless to foods. There is no evidence that food cooked or kept in aluminum vessels is rendered injurious to health. Small, useful and ornamental articles are made of it. It is difficult to solder, so the parts are often welded together.

Aluminum in very fine flakes is used in paint to protect metals and to hide imperfections in the surface painted. It is also used in foils and flash powders for photography. Aluminum plating is also employed. Under wartime conditions the use of aluminum in airplanes overshadows all other uses.

An important property of aluminum is that it has little or no effect on the color of materials contained or treated in vessels made of it. This is due to the fact that the compounds of aluminum are colorless. Aluminum vessels are used in the manufacture of varnishes, cosmetics, white paints, and other products, in which clear and light colors are desired. In some countries decrees provide for the use of aluminum for such things as tubes for toothpastes and cosmetics, to economize on lead and tin.

Small aluminum articles are anodized by using them as anodes for a few seconds, so that they receive a very thin coating of oxide. This adheres firmly and can be attractively colored by dyestuffs.

Ordinary aluminum is about 99.5 per cent pure. "Purest" aluminum is 99.99 per cent pure. This metal is about two thirds the conductivity of copper, is softer than ordinary aluminum, and may be sprayed on in coats as thick as one-tenth millimeter. It is resistant to corrosion. In the manufacture of coatings, as for electric cables, this new metal is more satisfactory than lead since it is lighter and more firm. Sprayed on glass, for mirrors, it is a better reflector and lasts longer than silver as a coating for the mirrors of large astronomical telescopes like the mirror of the great Palomar telescope.

Aluminum has been used to a considerable extent in place of copper as an electric conductor in transmission lines. As aluminum wire weighs half as much as a copper wire of the same conducting power, and does not produce so great a stress on the supports. Aluminum is found in hundreds of alloys." 8
• "When a mixture of aluminum powder and iron(III) oxide (called thermite) is ignited, it reacts in a spectacular incandescent shower, producing molten iron. The molten iron from the reaction of thermite has been used for welding.

A newly exposed aluminum surface quickly dulls as the metal reacts with oxygen in air to form the oxide. The oxide coating adheres tightly to the surface and prevents further reaction of the metal. This is an obvious advantage in many applications, since corroding is not a problem, as it is with iron. But it is also a source of an environmental problem: Aluminum cans do not disintegrate by corrosion the way coated steel cans do, so they accumulate along roadways and in land fills. Recycling of aluminum is an attractive solution to this problem and also helps save electrical energy that would ordinarily be needed for the preparation of new metal from its ore.

Commercial drain cleaners are principally sodium hydroxide, and some contain small pieces of aluminum, which fizz when the cleaner comes in contact with water. The fizzing results from the formation of hydrogen bubbles as the aluminum metal reacts with the hydroxide ion in aqueous solution." 9
• "For improving the strength of aluminum materials, there is no better single element to add than scandium. Scandium-aluminum alloys are strong mainly because grain size is reduced. Small grains embedded in a metal lattice inhibit the transfer of a disturbance (such as caused by a forceful blow) through the material. Dislocation of the lattice is impeded at grain boundaries, and vibration is dispersed better when very small grains are distributed throughout the material.

Sc-Al alloys also exhibit excellent thermal stability. This feature makes a high-strength aluminum alloy easier to weld. It also reduces recrystallization. Crystallization weakens any object by restoring a rigid lattice that can have a higher shear tendency, leading to loss of strength. This tends to occur in items like bicycle frames and baseball bats that are cold-worked in their manufacture. Using Sc-Al alloys can alleviate this problem.

Recent studies have shown that the addition of small amounts of zirconium to scandium-aluminum alloys can have a dramatic effect on strength and thermal stability." 10
• "Aluminum is an excellent conductor of electricity and heat. In addition, its surface is highly reflective. Of the light (85-90 percent) incident on an aluminum surface, most is reflected, rather than being absorbed. Because pure aluminum by itself is too soft to use as a structural material (in aircraft, for example, where its light weight is of utmost importance), other elements are alloyed with aluminum to make it strong, machinable, and formable into many useful shapes." 11
• "Aluminum metal is also much more expensive to obtain from its ores than iron metal is. This fact is what makes recycling aluminum products so extremely important. Not only does recycling mean that less aluminum ends up in landfills, it simply makes good economic sense to recycle aluminum. It takes only 5 percent as much energy to recycle an aluminum product as it takes to extract aluminum ore from the ground, reduce the ore to the metal, and then fashion the metal into a useful product. Using aluminum to make soft-drink cans may be extremely convenient, but the convenience is justified only if the cans are recycled." 12
• "It is difficult to imagine modern society without aluminum products. Most of the following uses of aluminum are familiar to daily life and activities.

Aluminum products are common around the house. Aluminum metal is used in the manufacture of a wide variety of cans, cooking utensils, and food packages. Aluminum foil is a common kitchen item. Home construction materials - doors, siding, windows, screens, and rain gutters - are made of aluminum.

Because of its light weight, aluminum finds many applications in transpurtation and in aerospace. Aluminum is used extensively in the manufacture of aircraft frames, engines, landing gear, and cabins. Motor vehicle materials - radiators, engine blocks, transmissions, and body panels - can all be made of aluminum. Rapid transit vehicles - light rail trains, for example - often are constructed of aluminum. Locomotives, freight cars, and cargo containers may be made of aluminum. Boat hulls may be constructed of aluminum. Also, to save weight, satellites are made of aluminum. Aluminum's light weight is also useful in sporting equipment. Skis, baseball bats, and tennis rackets are primarily made of aluminum.

Manufacturers often take advantage of aluminum's corrosion resistance. Highway signs are almost exclusively made of aluminum. Electrical wire and cable may be made of aluminum. Aluminum often is used for coating mirrors because of its high optical reflectivity.

Aluminum powder is used as a pigment in paints and for its vigorous reactivity in rocket fuels, explosives, and fireworks. In particulate form, aluminum oxide is used as an abrasive in emery board and sandpaper. Aluminum chloride and other aluminum compounds are common in antiperspirants." 13
• "Hydrangea colors ultimately depend on the availability of aluminum ions (Al3+) within the soil. The role of aluminum has been known since the 1940s, but it did not reach the mainstream horticultural literature until about the past two decades, and the exact mechanism was only recently defined. Aluminum ions are mobile in acidic soil because of the ready availibility of other ions they can react with, which can be taken up in the hydrangea to the bloom where they interact with the normally red pigment. But in neutral to basic soil, the ions combine with hydroxide ions (OH-) to form immobile aluminum hydroxide, Al(OH)3. Consequently, for the bluing of hydrangea blooms, one needs both aluminum ions and acidic soil. The best soil aadditive for bluing is one that combines both, such as commercially available aluminum sulfate, Al2(SO4)3. Conversely, if one wishes to change blue blooming hydrangea to red-blooming, adding lime (calcium hydroxide, Ca(OH)2) results in basic soil and the desired color transition." 14

Propiedades físicas

Punto de fusion:15*  660.32 °C = 933.47 K = 1220.576 °F
Punto de ebullición:15* 2519 °C = 2792.15 K = 4566.2 °F
Punto de sublimación:15 
Triple punto:15 
Punto crítico:15 
Densidad:16  2.7 g/cm3

* - at 1 atm

Configuración electronica

Configuración electronica: [Ne] 3s2 3p1
Bloquear: p
Ocupado más alto nivel de energía: 3
Electrones de valencia: 3

Números cuánticos:

n = 3
ℓ = 1
m = -1
ms = +½

Vinculación

electronegatividad (escala de Pauling):17 1.61
Electropositivity (escala de Pauling): 2.39
Afinidad electronica:18 0.43283 eV
estados de oxidación: +3
Función del trabajo:19 4.19 eV = 6.71238E-19 J

potencial de ionización   eV 20  kJ/mol  
1 5.98577    577.5
2 18.82856    1816.7
3 28.44765    2744.8
4 119.992    11577.5
potencial de ionización   eV 20  kJ/mol  
5 153.825    14841.9
6 190.49    18379.5
7 241.76    23326.3
8 284.66    27465.5
potencial de ionización   eV 20  kJ/mol  
9 330.13    31852.7
10 398.75    38473.5
11 442    42646.5
12 2085.98    201266.4
13 2304.141    222315.8

termoquímica

Calor especifico: 0.897 J/g°C 21 = 24.202 J/mol°C = 0.214 cal/g°C = 5.785 cal/mol°C
Conductividad térmica: 237 (W/m)/K, 27°C 22
Calor de fusión: 10.79 kJ/mol 23 = 399.9 J/g
Calor de vaporización: 293.4 kJ/mol 24 = 10874.1 J/g
Estado de la materia Entalpía de formación (ΔHf°)25 entropía (S°)25 Energía libre de Gibbs (ΔGf°)25
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 6.77 28.32568 0 0
(ℓ) 2.07 8.66088 8.42 35.22928 1.58 6.61072
(g) 78.00 326.352 39.30 164.4312 68.30 285.7672

isótopos

nucleido Masa 26 Media vida 26 spin nuclear 26 Energía de unión
21Al 21.02804(32)# <35 ns 1/2+# 133.24 MeV
22Al 22.01952(10)# 59(3) ms (3)+ 149.70 MeV
23Al 23.007267(20) 470(30) ms 5/2+# 168.95 MeV
24Al 23.9999389(30) 2.053(4) s 4+ 184.47 MeV
25Al 24.9904281(5) 7.183(12) s 5/2+ 200.93 MeV
26Al 25.98689169(6) 7.17(24)E+5 a 5+ 212.72 MeV
27Al 26.98153863(12) ESTABLE 5/2+ 225.45 MeV
28Al 27.98191031(14) 2.2414(12) min 3+ 233.52 MeV
29Al 28.9804450(13) 6.56(6) min 5/2+ 242.53 MeV
30Al 29.982960(15) 3.60(6) s 3+ 248.74 MeV
31Al 30.983947(22) 644(25) ms (3/2,5/2)+ 255.88 MeV
32Al 31.98812(9) 31.7(8) ms 1+ 259.29 MeV
33Al 32.99084(8) 41.7(2) ms (5/2+)# 265.50 MeV
34Al 33.99685(12) 56.3(5) ms 4-# 267.98 MeV
35Al 34.99986(19) 38.6(4) ms 5/2+# 273.26 MeV
36Al 36.00621(23) 90(40) ms 274.81 MeV
37Al 37.01068(36) 10.7(13) ms 3/2+ 279.15 MeV
38Al 38.01723(78) 7.6(6) ms 280.70 MeV
39Al 39.02297(158) 7.6(16) ms 3/2+# 284.12 MeV
40Al 40.03145(75)# 10# ms [>260 ns] 283.81 MeV
41Al 41.03833(86)# 2# ms [>260 ns] 3/2+# 285.36 MeV
42Al 42.04689(97)# 1# ms 285.98 MeV
Los valores marcados con # no son puramente derivan de los datos experimentales, pero al menos en parte, de las tendencias sistemáticas. Hace girar con débiles argumentos de asignación se incluyen entre paréntesis. 26

reacciones

Abundancia

Tierra - Los compuestos de origen: oxides 43
Tierra - Agua de mar: 0.002 mg/L 44
Tierra -  Corteza:  82300 mg/kg = 8.23% 44
Tierra -  Manto:  1.8% 45
Tierra -  Total:  1.41% 46
Planeta mercurio) -  Total:  1.08% 46
Venus -  Total:  1.48% 46
condritas - Total: 6×104 (relative to 106 atoms of Si) 47
Cuerpo humano - Total: 0.00009% 48

Compuestos

Precios





Información de seguridad


Ficha de datos de seguridad de materiales - ACI Alloys, Inc.

Para más información

Enlaces externos:

revistas:
(1) Castelvecchi, Davide. Let There be Aluminum-42. Science News, October 27, 2007, pp 260.

Fuentes

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