Chemical reactions with aluminum. Chemical properties of aluminum. Corrosion of aluminum in water
(according to Pauling)
Aluminum- an element of the main subgroup of the third group of the third period of the periodic system of chemical elements of D.I. Mendeleev, atomic number 13. Denoted by the symbol Al (Aluminium). Belongs to the group of light metals. The most common metal and the third most abundant (after oxygen and silicon) chemical element in the earth's crust.
The simple substance aluminum (CAS number: 7429-90-5) is a lightweight, paramagnetic silver-white metal that can be easily formed, cast, and machined. Aluminum has high thermal and electrical conductivity and resistance to corrosion due to the rapid formation of strong oxide films that protect the surface from further interaction.
According to some biological studies, the intake of aluminum in the human body was considered a factor in the development of Alzheimer's disease, but these studies were later criticized and the conclusion about the connection between one and the other was refuted.
Story
Aluminum was first obtained by Hans Oersted in 1825 by the action of potassium amalgam on aluminum chloride followed by distillation of mercury.
Receipt
The modern production method was developed independently by the American Charles Hall and the Frenchman Paul Héroux. It consists of dissolving aluminum oxide Al 2 O 3 in a melt of cryolite Na 3 AlF 6 followed by electrolysis using graphite electrodes. This production method requires a lot of electricity, and therefore became popular only in the 20th century.
To produce 1 ton of crude aluminum, 1.920 tons of alumina, 0.065 tons of cryolite, 0.035 tons of aluminum fluoride, 0.600 tons of anode mass and 17 thousand kWh of DC electricity are required.
Physical properties
The metal is silver-white in color, light, density - 2.7 g/cm³, melting point for technical aluminum - 658 °C, for high-purity aluminum - 660 °C, specific heat of fusion - 390 kJ/kg, boiling point - 2500 ° C, specific heat of evaporation - 10.53 MJ/kg, temporary resistance of cast aluminum - 10-12 kg/mm², deformable - 18-25 kg/mm², alloys - 38-42 kg/mm².
Brinell hardness is 24-32 kgf/mm², high ductility: technical - 35%, pure - 50%, rolled into thin sheets and even foil.
Aluminum has high electrical and thermal conductivity, 65% of the electrical conductivity of copper, and has high light reflectivity.
Aluminum forms alloys with almost all metals.
Being in nature
Natural aluminum consists almost entirely of a single stable isotope, 27Al, with traces of 26Al, a radioactive isotope with a half-life of 720,000 years produced in the atmosphere by bombardment of nuclei argon cosmic ray protons.
In terms of prevalence in nature, it ranks 1st among metals and 3rd among elements, second only to oxygen and silicon. The percentage of aluminum content in the earth's crust, according to various researchers, ranges from 7.45 to 8.14% of the mass of the earth's crust.
In nature, aluminum is found only in compounds (minerals). Some of them:
- Bauxite - Al 2 O 3. H 2 O (with impurities SiO 2, Fe 2 O 3, CaCO 3)
- Nephelines - KNa 3 4
- Alunites - KAl(SO 4) 2. 2Al(OH) 3
- Alumina (mixtures of kaolins with sand SiO 2, limestone CaCO 3, magnesite MgCO 3)
- Corundum - Al 2 O 3
- Feldspar (orthoclase) - K 2 O×Al 2 O 3 ×6SiO 2
- Kaolinite - Al 2 O 3 × 2SiO 2 × 2H 2 O
- Alunite - (Na,K) 2 SO 4 ×Al 2 (SO 4) 3 ×4Al(OH) 3
- Beryl - 3BeO. Al 2 O 3 . 6SiO2
Natural waters contain aluminum in the form of low-toxic chemical compounds, for example, aluminum fluoride. The type of cation or anion depends, first of all, on the acidity of the aqueous medium. Aluminum concentrations in surface water bodies in Russia range from 0.001 to 10 mg/l.
Chemical properties
Aluminum hydroxide
Under normal conditions, aluminum is covered with a thin and durable oxide film and therefore does not react with classical oxidizing agents: with H 2 O (t°); O 2, HNO 3 (without heating). Thanks to this, aluminum is practically not subject to corrosion and is therefore widely in demand in modern industry. However, when the oxide film is destroyed (for example, upon contact with solutions of ammonium salts NH 4 +, hot alkalis or as a result of amalgamation), aluminum acts as an active reducing metal.
Reacts easily with simple substances:
- with oxygen: 4Al + 3O 2 = 2Al 2 O 3
- with halogens: 2Al + 3Br 2 = 2AlBr 3
- reacts with other non-metals when heated:
- with sulfur, forming aluminum sulfide: 2Al + 3S = Al 2 S 3
- with nitrogen, forming aluminum nitride: 2Al + N 2 = 2AlN
- with carbon, forming aluminum carbide: 4Al + 3C = Al 4 C 3
The method, invented almost simultaneously by Charles Hall in France and Paul Héroux in the USA in 1886 and based on the production of aluminum by electrolysis of alumina dissolved in molten cryolite, laid the foundation for the modern method of aluminum production. Since then, due to improvements in electrical engineering, aluminum production has improved. A notable contribution to the development of alumina production was made by Russian scientists K. I. Bayer, D. A. Penyakov, A. N. Kuznetsov, E. I. Zhukovsky, A. A. Yakovkin and others.
The first aluminum smelter in Russia was built in 1932 in Volkhov. The metallurgical industry of the USSR in 1939 produced 47.7 thousand tons of aluminum, another 2.2 thousand tons were imported.
In Russia, the de facto monopolist in aluminum production is Russian Aluminum OJSC, which accounts for about 13% of the world aluminum market and 16% of alumina.
The world's reserves of bauxite are practically limitless, that is, they are incommensurate with the dynamics of demand. Existing facilities can produce up to 44.3 million tons of primary aluminum per year. It should also be taken into account that in the future some of the applications of aluminum may be reoriented to the use of, for example, composite materials.
Application
A piece of aluminum and an American coin.
Widely used as a construction material. The main advantages of aluminum in this quality are lightness, malleability for stamping, corrosion resistance (in air, aluminum is instantly covered with a durable film of Al 2 O 3, which prevents its further oxidation), high thermal conductivity, and non-toxicity of its compounds. In particular, these properties have made aluminum extremely popular in the production of cookware, aluminum foil in the food industry and for packaging.
The main disadvantage of aluminum as a structural material is its low strength, so it is usually alloyed with a small amount of copper and magnesium - duralumin alloy.
The electrical conductivity of aluminum is only 1.7 times less than that of copper, while aluminum is approximately 2 times cheaper. Therefore, it is widely used in electrical engineering for the manufacture of wires, their shielding, and even in microelectronics for the manufacture of conductors in chips. The lower electrical conductivity of aluminum (37 1/ohm) compared to copper (63 1/ohm) is compensated by increasing the cross-section of aluminum conductors. The disadvantage of aluminum as an electrical material is its strong oxide film, which makes soldering difficult.
- Due to its complex of properties, it is widely used in heating equipment.
- Aluminum and its alloys retain strength at ultra-low temperatures. Due to this, it is widely used in cryogenic technology.
- High reflectivity, combined with low cost and ease of deposition, makes aluminum an ideal material for making mirrors.
- In the production of building materials as a gas-forming agent.
- Aluminizing imparts corrosion and scale resistance to steel and other alloys, such as piston internal combustion engine valves, turbine blades, oil platforms, heat exchange equipment, and also replaces galvanizing.
- Aluminum sulfide is used to produce hydrogen sulfide.
- Research is underway to develop foamed aluminum as an especially strong and lightweight material.
As a reducing agent
- As a component of thermite, mixtures for aluminothermy
- Aluminum is used to recover rare metals from their oxides or halides.
Aluminum alloys
The structural material usually used is not pure aluminum, but various alloys based on it.
— Aluminum-magnesium alloys have high corrosion resistance and are well welded; They are used, for example, to make the hulls of high-speed ships.
— Aluminum-manganese alloys are in many ways similar to aluminum-magnesium alloys.
— Aluminum-copper alloys (in particular, duralumin) can be subjected to heat treatment, which greatly increases their strength. Unfortunately, heat-treated materials cannot be welded, so aircraft parts are still connected with rivets. An alloy with a higher copper content is very similar in color to gold, and is sometimes used to imitate the latter.
— Aluminum-silicon alloys (silumins) are best suited for casting. Cases of various mechanisms are often cast from them.
— Complex alloys based on aluminum: avial.
— Aluminum goes into a superconducting state at a temperature of 1.2 Kelvin.
Aluminum as an additive to other alloys
Aluminum is an important component of many alloys. For example, in aluminum bronzes the main components are copper and aluminum. In magnesium alloys, aluminum is most often used as an additive. For the manufacture of spirals in electric heating devices, fechral (Fe, Cr, Al) is used (along with other alloys).
Jewelry
When aluminum was very expensive, a variety of jewelry was made from it. The fashion for them immediately passed when new technologies for its production appeared, which reduced the cost many times over. Nowadays, aluminum is sometimes used in the production of costume jewelry.
Glass making
Fluoride, phosphate and aluminum oxide are used in glass making.
Food industry
Aluminum is registered as a food additive E173.
Aluminum and its compounds in rocket technology
Aluminum and its compounds are used as a highly efficient propellant in two-propellant rocket propellants and as a combustible component in solid rocket propellants. The following aluminum compounds are of greatest practical interest as rocket fuel:
— Aluminum: fuel in rocket fuels. Used in the form of powder and suspensions in hydrocarbons, etc.
— Aluminum hydride
— Aluminum boranate
— Trimethylaluminum
— Triethylaluminum
— Tripropylaluminum
Theoretical characteristics of fuels formed by aluminum hydride with various oxidizers.
| Oxidizer | Specific thrust (P1, sec) | Combustion temperature °C | Fuel density, g/cm³ | Speed increase, ΔV id, 25, m/s | Weight content fuel,% |
|---|---|---|---|---|---|
| Fluorine | 348,4 | 5009 | 1,504 | 5328 | 25 |
| Tetrafluorohydrazine | 327,4 | 4758 | 1,193 | 4434 | 19 |
| ClF 3 | 287,7 | 4402 | 1,764 | 4762 | 20 |
| ClF5 | 303,7 | 4604 | 1,691 | 4922 | 20 |
| Perchloryl fluoride | 293,7 | 3788 | 1,589 | 4617 | 47 |
| Oxygen fluoride | 326,5 | 4067 | 1,511 | 5004 | 38,5 |
| Oxygen | 310,8 | 4028 | 1,312 | 4428 | 56 |
| Hydrogen peroxide | 318,4 | 3561 | 1,466 | 4806 | 52 |
| N2O4 | 300,5 | 3906 | 1,467 | 4537 | 47 |
| Nitric acid | 301,3 | 3720 | 1,496 | 4595 | 49 |
Aluminum in world culture
The poet Andrei Voznesensky wrote the poem “Autumn” in 1959, in which he used aluminum as an artistic image:
...And behind the window in the young frost
there are fields of aluminum...
Viktor Tsoi wrote the song “Aluminum Cucumbers” with the chorus:
Planting aluminum cucumbers
On a tarpaulin field
I plant aluminum cucumbers
On a tarpaulin field
Toxicity
It has a slight toxic effect, but many water-soluble inorganic aluminum compounds remain in a dissolved state for a long time and can have a harmful effect on humans and warm-blooded animals through drinking water. The most toxic are chlorides, nitrates, acetates, sulfates, etc. For humans, the following doses of aluminum compounds (mg/kg body weight) have a toxic effect when ingested: aluminum acetate - 0.2-0.4; aluminum hydroxide - 3.7-7.3; aluminum alum - 2.9. Primarily affects the nervous system (accumulates in nervous tissue, leading to severe disorders of the central nervous system). However, the neurotoxicity of aluminum has been studied since the mid-1960s, since the accumulation of the metal in the human body is prevented by its elimination mechanism. Under normal conditions, up to 15 mg of the element per day can be excreted in the urine. Accordingly, the greatest negative effect is observed in people with impaired renal excretory function.
Additional Information
— Aluminum hydroxide
— Encyclopedia about aluminum
— Aluminum connections
— International Aluminum Institute
Aluminum, Aluminum, Al (13)
Binders containing aluminum have been known since ancient times. However, alum (Latin Alumen or Alumin, German Alaun), which is mentioned, in particular, by Pliny, was understood in ancient times and in the Middle Ages as various substances. In Ruland's Alchemical Dictionary, the word Alumen, with the addition of various definitions, is given in 34 meanings. In particular, it meant antimony, Alumen alafuri - alkaline salt, Alumen Alcori - nitrum or alkali alum, Alumen creptum - tartar (tartar) of good wine, Alumen fascioli - alkali, Alumen odig - ammonia, Alumen scoriole - gypsum, etc. Lemery, the author of the famous “Dictionary of Simple Pharmaceutical Products” (1716), also provides a large list of varieties of alum.
Until the 18th century aluminum compounds (alum and oxide) could not be distinguished from other compounds similar in appearance. Lemery describes the alum as follows: “In 1754. Marggraf isolated from an alum solution (by the action of alkali) a precipitate of aluminum oxide, which he called “alum earth” (Alaunerde), and established its difference from other earths. Soon alum earth received the name alumina (Alumina or Alumine). In 1782, Lavoisier expressed the idea that aluminum was an oxide of an unknown element. In his Table of Simple Bodies, Lavoisier placed Alumine among the “simple bodies, salt-forming, earthy.” Here are synonyms for the name alumina: argile, alum. earth, foundation of alum. The word argilla, or argilla, as Lemery points out in his dictionary, comes from the Greek. pottery clay. Dalton in his “New System of Chemical Philosophy” gives a special sign for aluminum and gives a complex structural (!) formula for alum.
After the discovery of alkali metals using galvanic electricity, Davy and Berzelius unsuccessfully tried to isolate metallic aluminum from alumina in the same way. Only in 1825 was the problem solved by the Danish physicist Oersted using a chemical method. He passed chlorine through a hot mixture of alumina and coal, and the resulting anhydrous aluminum chloride was heated with potassium amalgam. After evaporation of mercury, writes Oersted, a metal similar in appearance to tin was obtained. Finally, in 1827, Wöhler isolated aluminum metal in a more efficient way - by heating anhydrous aluminum chloride with potassium metal.
Around 1807, Davy, who was trying to carry out the electrolysis of alumina, gave the name to the metal supposed to contain it aluminum (Alumium) or aluminum (Aluminum). The latter name has since become common in the USA, while in England and other countries the name Aluminum, later proposed by the same Davy, has been adopted. It is quite clear that all these names come from the Latin word alum (Alumen), about the origin of which there are different opinions, based on the evidence of various authors, dating back to antiquity.
A. M. Vasiliev, noting the unclear origin of this word, cites the opinion of a certain Isidore (obviously Isidore of Seville, a bishop who lived in 560 - 636, an encyclopedist who was engaged, in particular, in etymological research): “Alumen is called a lumen, so how it gives lumen (light, brightness) to paints when added during dyeing." However, this explanation, although very old, does not prove that the word alumen has precisely such origins. Here, only an accidental tautology is quite likely. Lemery (1716) in turn points out that the word alumen is related to the Greek (halmi), meaning salinity, brine, brine, etc.
Russian names for aluminum in the first decades of the 19th century. quite varied. Each of the authors of books on chemistry of this period obviously sought to propose its own title. Thus, Zakharov calls aluminum alumina (1810), Giese - alumium (1813), Strakhov - alum (1825), Iovsky - clay, Shcheglov - alumina (1830). In Dvigubsky's Store (1822 - 1830), alumina is called alumina, alumina, alumina (for example, phosphoric acid alumina), and the metal is called aluminum and aluminum (1824). Hess in the first edition of “Foundations of Pure Chemistry” (1831) uses the name alumina (Aluminium), and in the fifth edition (1840) - clay. However, he forms names for salts based on the term alumina, for example, alumina sulfate. Mendeleev in the first edition of “Fundamentals of Chemistry” (1871) uses the names aluminum and clay. In subsequent editions the word clay no longer appears.
Aluminum is an element of the main subgroup of group III, third period, with atomic number 13. Aluminum is a p-element. The outer energy level of an aluminum atom contains 3 electrons, which have the electronic configuration 3s 2 3p 1. Aluminum exhibits an oxidation state of +3.
Belongs to the group of light metals. The most common metal and the third most abundant chemical element in the earth's crust (after oxygen and silicon).
The simple substance aluminum is a light, paramagnetic metal of silvery-white color, easy to form, cast, and machine. Aluminum has high thermal and electrical conductivity and resistance to corrosion due to the rapid formation of strong oxide films that protect the surface from further interaction.
Chemical properties of aluminum
Under normal conditions, aluminum is covered with a thin and durable oxide film and therefore does not react with classical oxidizing agents: with H 2 O (t°); O 2, HNO 3 (without heating). Thanks to this, aluminum is practically not subject to corrosion and is therefore widely in demand in modern industry. When the oxide film is destroyed, aluminum acts as an active reducing metal.
1. Aluminum easily reacts with simple non-metallic substances:
4Al + 3O 2 = 2Al 2 O 3
2Al + 3Cl 2 = 2AlCl 3,
2Al + 3 Br 2 = 2AlBr 3
2Al + N 2 = 2AlN
2Al + 3S = Al 2 S 3
4Al + 3C = Al 4 C 3
Aluminum sulfide and carbide are completely hydrolyzed:
Al 2 S 3 + 6H 2 O = 2Al(OH) 3 + 3H 2 S
Al 4 C 3 + 12H 2 O = 4Al(OH) 3 + 3CH 4
2. Aluminum reacts with water
(after removing the protective oxide film):
2Al + 6H 2 O = 2Al(OH) 3 + 3H 2
3. Aluminum reacts with alkalis
2Al + 2NaOH + 6H 2 O = 2Na + 3H 2
2(NaOHH 2 O) + 2Al = 2NaAlO 2 + 3H 2
First, the protective oxide film dissolves: Al 2 O 3 + 2NaOH + 3H 2 O = 2Na.
Then the reactions occur: 2Al + 6H 2 O = 2Al(OH) 3 + 3H 2, NaOH + Al(OH) 3 = Na,
or in total: 2Al + 6H 2 O + 2NaOH = Na + 3H 2,
and as a result, aluminates are formed: Na - sodium tetrahydroxoaluminate Since the aluminum atom in these compounds is characterized by a coordination number of 6, not 4, the actual formula of tetrahydroxo compounds is as follows: Na
4. Aluminum is easily dissolved in hydrochloric and dilute sulfuric acids:
2Al + 6HCl = 2AlCl3 + 3H2
2Al + 3H 2 SO 4 (dil) = Al 2 (SO 4) 3 + 3H 2
When heated, it dissolves in acids - oxidizing agents, forming soluble aluminum salts:
8Al + 15H 2 SO 4 (conc) = 4Al 2 (SO 4) 3 + 3H 2 S + 12H 2 O
Al + 6HNO 3 (conc) = Al(NO 3) 3 + 3NO 2 + 3H 2 O
5. Aluminum reduces metals from their oxides (aluminothermy):
8Al + 3Fe 3 O 4 = 4Al 2 O 3 + 9Fe
2Al + Cr 2 O 3 = Al 2 O 3 + 2Cr
Aluminum is an amphoteric metal. The electronic configuration of the aluminum atom is 1s 2 2s 2 2p 6 3s 2 3p 1. Thus, it has three valence electrons on its outer electron layer: 2 on the 3s and 1 on the 3p sublevel. Due to this structure, it is characterized by reactions as a result of which the aluminum atom loses three electrons from the outer level and acquires an oxidation state of +3. Aluminum is a highly reactive metal and exhibits very strong reducing properties.
Interaction of aluminum with simple substances
with oxygen
When absolutely pure aluminum comes into contact with air, aluminum atoms located in the surface layer instantly interact with oxygen in the air and form a thin, tens of atomic layers thick, durable oxide film of the composition Al 2 O 3, which protects aluminum from further oxidation. It is also impossible to oxidize large samples of aluminum even at very high temperatures. However, fine aluminum powder burns quite easily in a burner flame:
4Al + 3O 2 = 2Al 2 O 3
with halogens
Aluminum reacts very vigorously with all halogens. Thus, the reaction between mixed aluminum and iodine powders occurs already at room temperature after adding a drop of water as a catalyst. Equation for the interaction of iodine with aluminum:
2Al + 3I 2 =2AlI 3
Aluminum also reacts with bromine, which is a dark brown liquid, without heating. Simply add a sample of aluminum to liquid bromine: a violent reaction immediately begins, releasing a large amount of heat and light:
2Al + 3Br 2 = 2AlBr 3
The reaction between aluminum and chlorine occurs when heated aluminum foil or fine aluminum powder is added to a flask filled with chlorine. Aluminum burns effectively in chlorine according to the equation:
2Al + 3Cl 2 = 2AlCl 3
with sulfur
When heated to 150-200 o C or after igniting a mixture of powdered aluminum and sulfur, an intense exothermic reaction begins between them with the release of light:
— sulfide aluminum
with nitrogen
When aluminum reacts with nitrogen at a temperature of about 800 o C, aluminum nitride is formed:
with carbon
At a temperature of about 2000 o C, aluminum reacts with carbon and forms aluminum carbide (methanide), containing carbon in the -4 oxidation state, as in methane.
Interaction of aluminum with complex substances
with water
As mentioned above, a stable and durable oxide film of Al 2 O 3 prevents aluminum from oxidizing in air. The same protective oxide film makes aluminum inert towards water. When removing the protective oxide film from the surface by methods such as treatment with aqueous solutions of alkali, ammonium chloride or mercury salts (amalgiation), aluminum begins to react vigorously with water to form aluminum hydroxide and hydrogen gas:
with metal oxides
After igniting a mixture of aluminum with oxides of less active metals (to the right of aluminum in the activity series), an extremely violent, highly exothermic reaction begins. Thus, in the case of interaction of aluminum with iron (III) oxide, a temperature of 2500-3000 o C develops. As a result of this reaction, high-purity molten iron is formed:
2AI + Fe 2 O 3 = 2Fe + Al 2 O 3
This method of obtaining metals from their oxides by reduction with aluminum is called aluminothermy or aluminothermy.
with non-oxidizing acids
The interaction of aluminum with non-oxidizing acids, i.e. with almost all acids, except concentrated sulfuric and nitric acids, leads to the formation of an aluminum salt of the corresponding acid and hydrogen gas:
a) 2Al + 3H 2 SO 4 (diluted) = Al 2 (SO 4) 3 + 3H 2
2Al 0 + 6H + = 2Al 3+ + 3H 2 0 ;
b) 2AI + 6HCl = 2AICl3 + 3H2
with oxidizing acids
-concentrated sulfuric acid
The interaction of aluminum with concentrated sulfuric acid under normal conditions and at low temperatures does not occur due to an effect called passivation. When heated, the reaction is possible and leads to the formation of aluminum sulfate, water and hydrogen sulfide, which is formed as a result of the reduction of sulfur, which is part of sulfuric acid:
Such a deep reduction of sulfur from the oxidation state +6 (in H 2 SO 4) to the oxidation state -2 (in H 2 S) occurs due to the very high reducing ability of aluminum.
- concentrated nitric acid
Under normal conditions, concentrated nitric acid also passivates aluminum, which makes it possible to store it in aluminum containers. Just as in the case of concentrated sulfuric acid, the interaction of aluminum with concentrated nitric acid becomes possible with strong heating, and the reaction predominantly occurs:
- dilute nitric acid
The interaction of aluminum with diluted nitric acid compared to concentrated nitric acid leads to products of deeper nitrogen reduction. Instead of NO, depending on the degree of dilution, N 2 O and NH 4 NO 3 can be formed:
8Al + 30HNO 3(dil.) = 8Al(NO 3) 3 +3N 2 O + 15H 2 O
8Al + 30HNO 3(pure dilute) = 8Al(NO 3) 3 + 3NH 4 NO 3 + 9H 2 O
with alkalis
Aluminum reacts both with aqueous solutions of alkalis:
2Al + 2NaOH + 6H 2 O = 2Na + 3H 2
and with pure alkalis during fusion:
In both cases, the reaction begins with the dissolution of the protective film of aluminum oxide:
Al 2 O 3 + 2NaOH + 3H 2 O = 2Na
Al 2 O 3 + 2NaOH = 2NaAlO 2 + H 2 O
In the case of an aqueous solution, aluminum, cleared of the protective oxide film, begins to react with water according to the equation:
2Al + 6H 2 O = 2Al(OH) 3 + 3H 2
The resulting aluminum hydroxide, being amphoteric, reacts with an aqueous solution of sodium hydroxide to form soluble sodium tetrahydroxoaluminate:
Al(OH) 3 + NaOH = Na
Aluminum and its compounds
The main subgroup of group III of the periodic system consists of boron (B), aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).
As can be seen from the above data, all these elements were discovered in the 19th century.
Boron is a non-metal. Aluminum is a transition metal, while gallium, indium and thallium are full-fledged metals. Thus, with increasing radii of the atoms of the elements of each group of the periodic table, the metallic properties of simple substances increase.
The position of aluminum in D. I. Mendeleev’s table. Atomic structure, oxidation states
The element aluminum is located in group III, the main “A” subgroup, period 3 of the periodic system, serial number No. 13, relative atomic mass Ar(Al) = 27. Its neighbor on the left in the table is magnesium - a typical metal, and on the right - silicon - already non-metal. Consequently, aluminum must exhibit properties of some intermediate nature and its compounds are amphoteric.
Al +13) 2) 8) 3, p – element,
| Ground state 1s 2 2s 2 2p 6 3s 2 3p 1 |
| Excited state 1s 2 2s 2 2p 6 3s 1 3p 2 |
Aluminum exhibits an oxidation state of +3 in compounds:
Al 0 – 3 e - → Al +3
Physical properties
Aluminum in its free form is a silvery-white metal with high thermal and electrical conductivity. The melting point is 650 o C. Aluminum has a low density (2.7 g/cm 3) - about three times less than that of iron or copper, and at the same time it is a durable metal.
Being in nature
In terms of prevalence in nature, it ranks 1st among metals and 3rd among elements, second only to oxygen and silicon. The percentage of aluminum content in the earth's crust, according to various researchers, ranges from 7.45 to 8.14% of the mass of the earth's crust.
In nature, aluminum occurs only in compounds(minerals).
Some of them:
· Bauxite - Al 2 O 3 H 2 O (with impurities of SiO 2, Fe 2 O 3, CaCO 3)
· Nephelines - KNa 3 4
Alunites - KAl(SO 4) 2 2Al(OH) 3
· Alumina (mixtures of kaolins with sand SiO 2, limestone CaCO 3, magnesite MgCO 3)
Corundum - Al 2 O 3 (ruby, sapphire)
· Feldspar (orthoclase) - K 2 O×Al 2 O 3 ×6SiO 2
Kaolinite - Al 2 O 3 × 2SiO 2 × 2H 2 O
Alunite - (Na,K) 2 SO 4 ×Al 2 (SO 4) 3 ×4Al(OH) 3
· Beryl - 3BeO Al 2 O 3 6SiO 2
Chemical properties of aluminum and its compounds
Aluminum reacts easily with oxygen under normal conditions and is coated with an oxide film (which gives it a matte appearance).
Its thickness is 0.00001 mm, but thanks to it, aluminum does not corrode. To study the chemical properties of aluminum, the oxide film is removed. (Using sandpaper, or chemically: first dipping it into an alkali solution to remove the oxide film, and then into a solution of mercury salts to form an alloy of aluminum with mercury - amalgam).
WHAT IS ALUMINUM
Lightweight, durable, corrosion-resistant and functional - it is this combination of qualities that has made aluminum the main structural material of our time. Aluminum is in the houses we live in, the cars, trains and planes we travel on, in mobile phones and computers, on refrigerator shelves and in modern interiors. But 200 years ago little was known about this metal.
“What seemed impossible for centuries, what yesterday was just a daring dream, today becomes a real task, and tomorrow - an accomplishment.”
Sergei Pavlovich Korolev
scientist, designer, founder of practical astronautics
Aluminum – silvery-white metal, the 13th element of the periodic table. Incredible but true: aluminum is the most abundant metal on Earth, accounting for more than 8% of the total mass of the earth's crust, and it is the third most abundant chemical element on our planet after oxygen and silicon.
However, aluminum is not found in nature in its pure form due to its high chemical reactivity. That's why we learned about it relatively recently. Aluminum was formally produced only in 1824, and another half a century passed before its industrial production began.
Most often in nature, aluminum is found in the composition alum. These are minerals that combine two salts of sulfuric acid: one based on an alkali metal (lithium, sodium, potassium, rubidium or cesium), and the other based on a metal of the third group of the periodic table, mainly aluminum.
Alum is still used today in water purification, cooking, medicine, cosmetology, chemical and other industries. By the way, aluminum got its name thanks to alum, which in Latin was called alumen.
Corundum
Rubies, sapphires, emeralds and aquamarine are aluminum minerals.
The first two belong to corundum - this is aluminum oxide (Al 2 O 3) in crystalline form. It has natural transparency and is second only to diamonds in strength. Bulletproof glass, airplane windows, and smartphone screens are made using sapphire.
And one of the less valuable corundum minerals, emery, is used as an abrasive material, including to create sandpaper.
Today, almost 300 different aluminum compounds and minerals are known - from feldspar, which is the main rock-forming mineral on Earth, to ruby, sapphire or emerald, which are no longer so common.
Hans Christian Oersted(1777–1851) – Danish physicist, honorary member of the St. Petersburg Academy of Sciences (1830). Born in the city of Rudkörbing in the family of a pharmacist. In 1797 he graduated from the University of Copenhagen, in 1806 he became a professor.
But no matter how common aluminum was, its discovery became possible only when scientists had a new tool at their disposal that made it possible to break down complex substances into simpler ones - electricity.
And in 1824, using the process of electrolysis, the Danish physicist Hans Christian Oersted obtained aluminum. It was contaminated with impurities of potassium and mercury involved in chemical reactions, but this was the first time aluminum was produced.
Using electrolysis, aluminum is still produced today.
The raw material for aluminum production today is another aluminum ore common in nature - bauxite. This is a clayey rock consisting of various modifications of aluminum hydroxide with an admixture of oxides of iron, silicon, titanium, sulfur, gallium, chromium, vanadium, carbonate salts of calcium, iron and magnesium - almost half of the periodic table. On average, 1 ton of aluminum is produced from 4-5 tons of bauxite.
Bauxite
Bauxite was discovered by geologist Pierre Berthier in the south of France in 1821. The breed got its name after the area of Les Baux where it was found. About 90% of the world's bauxite reserves are concentrated in countries of the tropical and subtropical zones - Guinea, Australia, Vietnam, Brazil, India and Jamaica.
It is obtained from bauxite alumina. This is aluminum oxide Al 2 O 3, which has the form of a white powder and from which metal is produced by electrolysis in aluminum smelters.
Aluminum production requires huge amounts of electricity. To produce one ton of metal, about 15 MWh of energy is required - this is how much a 100-apartment building consumes for a whole month. Therefore, it makes the most sense to build aluminum smelters close to powerful and renewable energy sources. The most optimal solution is hydroelectric power stations, representing the most powerful of all types of “green energy”.
Properties of aluminum
Aluminum has a rare combination of valuable properties. This is one of the lightest metals in nature: it is almost three times lighter than iron, but at the same time it is strong, extremely ductile and not subject to corrosion, since its surface is always covered with a thin, but very durable oxide film. It is not magnetic, conducts electricity well, and forms alloys with almost all metals.
Easy
Three times lighter than iron
Lasting
Comparable in strength to steel
Plastic
Suitable for all types of mechanical processing
No corrosion
Thin oxide film protects against corrosion
Aluminum is easily processed by pressure, both hot and cold. It can be rolled, drawn, stamped. Aluminum does not burn, does not require special painting and is non-toxic, unlike plastic.
The malleability of aluminum is very high: sheets with a thickness of only 4 microns and the thinnest wire can be made from it. And ultra-thin aluminum foil is three times thinner than a human hair. In addition, compared to other metals and materials, it is more economical.
The high ability to form compounds with various chemical elements has given rise to many aluminum alloys. Even a small proportion of impurities significantly changes the characteristics of the metal and opens up new areas for its application. For example, the combination of aluminum with silicon and magnesium can be found literally on the road in everyday life - in the form of alloy wheels, engines, chassis elements and other parts of a modern car. And if you add zinc to the aluminum alloy, then perhaps you are holding it in your hands now, because this alloy is used in the production of cases for mobile phones and tablets. Meanwhile, scientists continue to invent new aluminum alloys.
Aluminum reserves
About 75% of the aluminum produced throughout the industry's existence is still in use today.
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