Oxidative properties of aluminum. Aluminum: chemical and physical properties

Preparation of potassium alum

Aluminum(Latin: Aluminum), – in the periodic table, aluminum is in the third period, in the main subgroup of the third group. Core charge +13. The electronic structure of the atom is 1s 2 2s 2 2p 6 3s 2 3p 1. The metallic atomic radius is 0.143 nm, the covalent radius is 0.126 nm, the conventional radius of the Al 3+ ion is 0.057 nm. Ionization energy Al – Al + 5.99 eV.

The most characteristic oxidation state of the aluminum atom is +3. Negative oxidation states rarely occur. There are free d-sublevels in the outer electron layer of the atom. Due to this, its coordination number in compounds can be not only 4 (AlCl 4-, AlH 4-, aluminosilicates), but also 6 (Al 2 O 3, 3+).

Historical background. The name Aluminum comes from the Latin. alumen - so back in 500 BC. called aluminum alum, which was used as a mordant for dyeing fabrics and for tanning leather. The Danish scientist H. K. Oersted in 1825, acting with potassium amalgam on anhydrous AlCl 3 and then distilling off mercury, obtained relatively pure Aluminum. The first industrial method of producing aluminum was proposed in 1854 by the French chemist A.E. Sainte-Clair Deville: the method consisted in the reduction of double aluminum and sodium chloride Na 3 AlCl 6 with metallic sodium. Similar in color to silver, Aluminum was very expensive at first. From 1855 to 1890, only 200 tons of aluminum were produced. The modern method of producing aluminum by electrolysis of cryolite-alumina melt was developed in 1886 simultaneously and independently by C. Hall in the USA and P. Heroux in France.

Being in nature

Aluminum is the most common metal in the earth's crust. It accounts for 5.5–6.6 mol. fraction% or 8 wt.%. Its main mass is concentrated in aluminosilicates. An extremely common product of the destruction of rocks formed by them is clay, the main composition of which corresponds to the formula Al 2 O 3. 2SiO2. 2H 2 O. From other natural forms of aluminum highest value have bauxite Al 2 O 3 . xH 2 O and minerals corundum Al 2 O 3 and cryolite AlF 3 . 3NaF.

Receipt

Currently, in industry, aluminum is produced by electrolysis of a solution of alumina Al 2 O 3 in molten cryolite. Al 2 O 3 must be fairly pure, since impurities are difficult to remove from smelted aluminum. The melting point of Al 2 O 3 is about 2050 o C, and cryolite is 1100 o C. A molten mixture of cryolite and Al 2 O 3 containing about 10 wt.% Al 2 O 3 is subjected to electrolysis, which melts at 960 o C and has electrical conductivity , density and viscosity, most favorable for the process. With the addition of AlF 3, CaF 2 and MgF 2, electrolysis becomes possible at 950 o C.

The electrolyzer for smelting aluminum is an iron casing lined with refractory bricks on the inside. Its bottom (under), assembled from blocks of compressed coal, serves as a cathode. The anodes are located on top: these are aluminum frames filled with coal briquettes.

Al 2 O 3 = Al 3+ + AlO 3 3-

Liquid aluminum is released at the cathode:

Al 3+ + 3e - = Al

Aluminum is collected at the bottom of the furnace, from where it is periodically released. Oxygen is released at the anode:

4AlO 3 3- – 12e - = 2Al 2 O 3 + 3O 2

Oxygen oxidizes graphite to carbon oxides. As the carbon burns, the anode is built up.

Aluminum is also used as an alloying additive to many alloys to impart heat resistance to them.

Physical properties of aluminum. Aluminum combines a very valuable set of properties: low density, high thermal and electrical conductivity, high ductility and good corrosion resistance. It can be easily forged, stamped, rolled, drawn. Aluminum is well welded by gas, contact and other types of welding. Aluminum lattice is cubic face-centered with parameter a = 4.0413 Å. The properties of Aluminum, like all metals, therefore depend on its purity. Properties of high purity Aluminum (99.996%): density (at 20 °C) 2698.9 kg/m 3 ; t pl 660.24 °C; boiling point about 2500 °C; coefficient of thermal expansion (from 20° to 100 °C) 23.86·10 -6; thermal conductivity (at 190 °C) 343 W/m·K, specific heat capacity (at 100 °С) 931.98 J/kg·K. ; electrical conductivity with respect to copper (at 20 °C) 65.5%. Aluminum has low strength (tensile strength 50–60 Mn/m2), hardness (170 Mn/m2 according to Brinell) and high ductility (up to 50%). During cold rolling, the tensile strength of Aluminum increases to 115 Mn/m2, hardness - up to 270 Mn/m2, relative elongation decreases to 5% (1 Mn/m2 ~ and 0.1 kgf/mm2). Aluminum is highly polished, anodized and has a high reflectivity close to silver (it reflects up to 90% of the incident light energy). Having a high affinity for oxygen, aluminum in air is covered with a thin but very strong film of Al 2 O 3 oxide, which protects the metal from further oxidation and determines its high anti-corrosion properties. The strength of the oxide film and its protective effect greatly decrease in the presence of impurities of mercury, sodium, magnesium, copper, etc. Aluminum is resistant to atmospheric corrosion, sea and fresh water, practically does not interact with concentrated or highly diluted nitric acid, organic acids, food products.

Chemical properties

When finely crushed aluminum is heated, it burns vigorously in air. Its interaction with sulfur proceeds similarly. The combination with chlorine and bromine occurs at ordinary temperatures, and with iodine - when heated. At very high temperatures aluminum also combines directly with nitrogen and carbon. On the contrary, it does not interact with hydrogen.

Aluminum is quite resistant to water. But if the protective effect of the oxide film is removed mechanically or by amalgamation, a vigorous reaction occurs:

Highly diluted and very concentrated HNO3 and H2SO4 have almost no effect on aluminum (in the cold), while at medium concentrations of these acids it gradually dissolves. Pure aluminum is quite resistant to hydrochloric acid, but ordinary industrial metal dissolves in it.

When aluminum is exposed to aqueous solutions of alkalis, the oxide layer dissolves, and aluminates are formed - salts containing aluminum as part of the anion:

Al 2 O 3 + 2NaOH + 3H 2 O = 2Na

Aluminum, devoid of a protective film, interacts with water, displacing hydrogen from it:

2Al + 6H 2 O = 2Al(OH) 3 + 3H 2

The resulting aluminum hydroxide reacts with excess alkali, forming hydroxoaluminate:

Al(OH) 3 + NaOH = Na

The overall equation for the dissolution of aluminum in an aqueous alkali solution:

2Al + 2NaOH + 6H 2 O = 2Na + 3H 2

Aluminum dissolves noticeably in solutions of salts that, due to their hydrolysis, have an acidic or alkaline reaction, for example, in a solution of Na 2 CO 3.

In the stress series it is located between Mg and Zn. In all its stable compounds, aluminum is trivalent.

The combination of aluminum with oxygen is accompanied by an enormous release of heat (1676 kJ/mol Al 2 O 3), significantly greater than that of many other metals. In view of this, when a mixture of the oxide of the corresponding metal with aluminum powder is heated, a violent reaction occurs, leading to the release of free metal from the taken oxide. The reduction method using Al (aluminothermy) is often used to obtain a number of elements (Cr, Mn, V, W, etc.) in a free state.

Aluminothermy is sometimes used for welding individual steel parts, in particular the joints of tram rails. The mixture used (“thermite”) usually consists of fine powders of aluminum and Fe 3 O 4 . It is ignited using a fuse made from a mixture of Al and BaO 2. The main reaction follows the equation:

8Al + 3Fe 3 O 4 = 4Al 2 O 3 + 9Fe + 3350 kJ

Moreover, the temperature develops around 3000 o C.

Aluminum oxide is a white, very refractory (mp 2050 o C) and insoluble in water mass. Natural Al 2 O 3 (mineral corundum), as well as those obtained artificially and then highly calcined, are distinguished by high hardness and insolubility in acids. Al 2 O 3 (so-called alumina) can be converted into a soluble state by fusion with alkalis.

Typically, natural corundum contaminated with iron oxide, due to its extreme hardness, is used to make grinding wheels, whetstones, etc. In finely crushed form, it is called emery and is used to clean metal surfaces and make sandpaper. For the same purposes, Al 2 O 3 is often used, obtained by fusing bauxite (technical name - alundum).

Transparent colored corundum crystals - red ruby ​​- an admixture of chromium - and blue sapphire - an admixture of titanium and iron - precious stones. They are also obtained artificially and used for technical purposes, for example, for the manufacture of parts for precision instruments, watch stones, etc. Ruby crystals containing a small admixture of Cr 2 O 3 are used as quantum generators - lasers that create a directed beam of monochromatic radiation.

Due to the insolubility of Al 2 O 3 in water, the hydroxide Al(OH) 3 corresponding to this oxide can be obtained only indirectly from salts. The preparation of hydroxide can be represented as the following scheme. Under the action of alkalis, OH – ions are gradually replaced by 3+ water molecules in aqua complexes:

3+ + OH - = 2+ + H 2 O

2+ + OH - = + + H 2 O

OH - = 0 + H 2 O

Al(OH) 3 is a voluminous gelatinous precipitate white, practically insoluble in water, but easily soluble in acids and strong alkalis. It therefore has an amphoteric character. However, its basic and especially acidic properties are rather weakly expressed. Aluminum hydroxide is insoluble in excess NH 4 OH. One of the forms of dehydrated hydroxide, aluminum gel, is used in technology as an adsorbent.

When interacting with strong alkalis, the corresponding aluminates are formed:

NaOH + Al(OH) 3 = Na

Aluminates of the most active monovalent metals are highly soluble in water, but due to strong hydrolysis, their solutions are stable only in the presence of a sufficient excess of alkali. Aluminates, produced from weaker bases, are almost completely hydrolyzed in solution and therefore can only be obtained dryly (by fusing Al 2 O 3 with oxides of the corresponding metals). Metaaluminates are formed, whose composition is derived from metaaluminum acid HAlO 2. Most of them are insoluble in water.

Al(OH) 3 forms salts with acids. Derivatives of most strong acids are highly soluble in water, but are quite significantly hydrolyzed, and therefore their solutions exhibit an acidic reaction. Soluble aluminum salts and weak acids are even more hydrolyzed. Due to hydrolysis, sulfide, carbonate, cyanide and some other aluminum salts cannot be obtained from aqueous solutions.

In an aqueous environment, the Al 3+ anion is directly surrounded by six water molecules. Such a hydrated ion is somewhat dissociated according to the scheme:

3+ + H 2 O = 2+ + OH 3 +

Its dissociation constant is 1. 10 -5, i.e. it is a weak acid (close in strength to acetic acid). The octahedral environment of Al 3+ with six water molecules is also preserved in crystalline hydrates of a number of aluminum salts.

Aluminosilicates can be considered as silicates in which part of the silicon-oxygen tetrahedra SiO 4 4 - is replaced by aluminum-oxygen tetrahedra AlO 4 5. Of the aluminosilicates, the most common are feldspars, which account for more than half the mass of the earth's crust. Their main representatives are minerals

orthoclase K 2 Al 2 Si 6 O 16 or K 2 O . Al 2 O 3 . 6SiO2

albite Na 2 Al 2 Si 6 O 16 or Na 2 O. Al 2 O 3 . 6SiO2

anorthite CaAl 2 Si 2 O 8 or CaO. Al 2 O 3 . 2SiO2

Minerals of the mica group are very common, for example muscovite Kal 2 (AlSi 3 O 10) (OH) 2. The mineral nepheline (Na, K) 2, which is used to produce alumina, soda products and cement, is of great practical importance. This production consists of the following operations: a) nepheline and limestone are sintered in tube furnaces at 1200 o C:

(Na, K) 2 + 2CaCO 3 = 2CaSiO 3 + NaAlO 2 + KAlO 2 + 2CO 2

b) the resulting mass is leached with water - a solution of sodium and potassium aluminates and CaSiO 3 slurry are formed:

NaAlO 2 + KAlO 2 + 4H 2 O = Na + K

c) CO 2 formed during sintering is passed through the aluminate solution:

Na + K + 2CO 2 = NaHCO 3 + KHCO 3 + 2Al(OH) 3

d) by heating Al(OH) 3 alumina is obtained:

2Al(OH) 3 = Al 2 O 3 + 3H 2 O

e) by evaporating the mother liquor, soda and potage are separated, and the previously obtained sludge is used for cement production.

When producing 1 ton of Al 2 O 3, 1 ton of soda products and 7.5 tons of cement are obtained.

Some aluminosilicates have a loose structure and are capable of ion exchange. Such silicates – natural and especially artificial – are used for water softening. In addition, due to their highly developed surface, they are used as catalyst supports, i.e. as materials impregnated with a catalyst.

Aluminum halides under normal conditions are colorless crystalline substances. In the series of aluminum halides, AlF 3 is very different in properties from its analogues. It is refractory, slightly soluble in water, and chemically inactive. The main method for producing AlF 3 is based on the action of anhydrous HF on Al 2 O 3 or Al:

Al 2 O 3 + 6HF = 2AlF 3 + 3H 2 O

Aluminum compounds with chlorine, bromine and iodine are fusible, very reactive and highly soluble not only in water, but also in many organic solvents. The interaction of aluminum halides with water is accompanied by a significant release of heat. In aqueous solution they are all highly hydrolyzed, but unlike typical acidic nonmetal halides, their hydrolysis is incomplete and reversible. Being noticeably volatile even under normal conditions, AlCl 3, AlBr 3 and AlI 3 smoke in moist air (due to hydrolysis). They can be obtained by direct interaction of simple substances.

The vapor densities of AlCl 3, AlBr 3 and AlI 3 at relatively low temperatures more or less exactly correspond to the double formulas - Al 2 Hal 6. The spatial structure of these molecules corresponds to two tetrahedra with a common edge. Each aluminum atom is bonded to four halogen atoms, and each of the central halogen atoms is bonded to both aluminum atoms. Of the two bonds of the central halogen atom, one is donor-acceptor, with aluminum functioning as an acceptor.

With halide salts of a number of monovalent metals, aluminum halides form complex compounds, mainly of the M 3 and M types (where Hal is chlorine, bromine or iodine). The tendency to addition reactions is generally very pronounced in the halides under consideration. This is precisely the reason for the most important technical use of AlCl 3 as a catalyst (in oil refining and in organic syntheses).

Of the fluoroaluminates, the greatest use (for the production of Al, F 2, enamels, glass, etc.) is Na 3 cryolite. Industrial production artificial cryolite is based on the treatment of aluminum hydroxide with hydrofluoric acid and soda:

2Al(OH) 3 + 12HF + 3Na 2 CO 3 = 2Na 3 + 3CO 2 + 9H 2 O

Chloro-, bromo- and iodoaluminates are obtained by fusing aluminum trihalides with halides of the corresponding metals.

Although aluminum does not react chemically with hydrogen, aluminum hydride can be obtained indirectly. It is a white amorphous mass of composition (AlH 3) n. Decomposes when heated above 105 o C with the release of hydrogen.

When AlH 3 interacts with basic hydrides in an ethereal solution, hydroaluminates are formed:

LiH + AlH 3 = Li

Hydridoaluminates are white solids. Rapidly decomposes with water. They are strong reducing agents. They are used (especially Li) in organic synthesis.

Aluminum sulfate Al 2 (SO 4) 3. 18H 2 O is obtained by the action of hot sulfuric acid on aluminum oxide or kaolin. It is used for water purification, as well as in the preparation of certain types of paper.

Potassium aluminum alum KAl(SO 4) 2. 12H 2 O is used in large quantities for tanning leather, and also in the dyeing industry as a mordant for cotton fabrics. In the latter case, the effect of alum is based on the fact that aluminum hydroxide formed as a result of its hydrolysis is deposited in the fabric fibers in a finely dispersed state and, adsorbing the dye, firmly holds it on the fiber.

Of the other aluminum derivatives, mention should be made of its acetate (otherwise acetic acid salt) Al(CH 3 COO) 3, used in dyeing fabrics (as a mordant) and in medicine (lotions and compresses). Aluminum nitrate is easily soluble in water. Aluminum phosphate is insoluble in water and acetic acid, but soluble in strong acids and alkalis.

Aluminum in the body. Aluminum is part of the tissues of animals and plants; in the organs of mammals, from 10 -3 to 10 -5% of Aluminum (on a crude basis) was found. Aluminum accumulates in the liver, pancreas and thyroid glands. In plant products, the Aluminum content ranges from 4 mg per 1 kg of dry matter (potatoes) to 46 mg (yellow turnips), in products of animal origin - from 4 mg (honey) to 72 mg per 1 kg of dry matter (beef). In the daily human diet, the aluminum content reaches 35–40 mg. Organisms that concentrate aluminum are known, for example, mosses (Lycopodiaceae), which contain up to 5.3% aluminum in their ash, and mollusks (Helix and Lithorina), which contain 0.2–0.8% aluminum in their ash. By forming insoluble compounds with phosphates, aluminum disrupts the nutrition of plants (absorption of phosphates by roots) and animals (absorption of phosphates in the intestines).

Geochemistry of aluminum. The geochemical features of aluminum are determined by its high affinity for oxygen (in minerals, aluminum is included in oxygen octahedra and tetrahedrons), constant valence (3), and low solubility of most natural compounds. In endogenous processes during the solidification of magma and the formation of igneous rocks, aluminum enters the crystal lattice of feldspars, micas and other minerals - aluminosilicates. In the biosphere, aluminum is a weak migrant; it is scarce in organisms and the hydrosphere. In a humid climate, where the decomposing remains of abundant vegetation form many organic acids, aluminum migrates in soils and waters in the form of organomineral colloidal compounds; aluminum is adsorbed by colloids and deposited in the lower part of soils. The bond between aluminum and silicon is partially broken and in some places in the tropics minerals are formed - aluminum hydroxides - boehmite, diaspore, hydrargillite. Most of the aluminum is part of aluminosilicates - kaolinite, beidellite and other clay minerals. Weak mobility determines the residual accumulation of aluminum in the weathering crust of the humid tropics. As a result, eluvial bauxite is formed. In past geological epochs, bauxite also accumulated in lakes and coastal zones of seas in tropical regions (for example, sedimentary bauxites of Kazakhstan). In steppes and deserts, where there is little living matter and the waters are neutral and alkaline, aluminum almost does not migrate. The migration of aluminum is most energetic in volcanic areas, where highly acidic river and groundwater rich in aluminum are observed. In places where acidic waters mix with alkaline sea waters (at the mouths of rivers and others), aluminum precipitates with the formation of bauxite deposits.

Application of Aluminum. The combination of physical, mechanical and chemical properties of Aluminum determines its widespread use in almost all areas of technology, especially in the form of its alloys with other metals. In electrical engineering, Aluminum successfully replaces copper, especially in the production of massive conductors, for example, in overhead lines, high-voltage cables, switchgear busbars, transformers (the electrical conductivity of Aluminum reaches 65.5% of the electrical conductivity of copper, and it is more than three times lighter than copper; with a cross section providing the same conductivity, the mass of aluminum wires is half that of copper). Ultra-pure Aluminum is used in the production of electrical capacitors and rectifiers, the action of which is based on the ability of the Aluminum oxide film to pass electric current in only one direction. Ultrapure Aluminum, purified by zone melting, is used for the synthesis of semiconductor compounds of type A III B V, used for the production of semiconductor devices. Pure Aluminum is used in the production of various types of mirror reflectors. High-purity aluminum is used to protect metal surfaces from atmospheric corrosion (cladding, aluminum paint). Possessing a relatively low neutron absorption cross section, aluminum is used as a structural material in nuclear reactors.

Large-capacity aluminum tanks store and transport liquid gases (methane, oxygen, hydrogen, etc.), nitrogen and acetic acid, clean water, hydrogen peroxide and edible oils. Aluminum is widely used in equipment and apparatus food industry, for packaging food products(in the form of foil), for the production of various types of household products. The consumption of aluminum for finishing buildings, architectural, transport and sports structures has increased sharply.

In metallurgy, Aluminum (in addition to alloys based on it) is one of the most common alloying additives in alloys based on Cu, Mg, Ti, Ni, Zn and Fe. Aluminum is also used to deoxidize steel before pouring it into a mold, as well as in the processes of producing certain metals using the aluminothermy method. Based on Aluminum, SAP (sintered aluminum powder) was created using powder metallurgy, which has high heat resistance at temperatures above 300 °C.

Aluminum is used in the production of explosives (ammonal, alumotol). Various aluminum compounds are widely used.

Aluminum production and consumption is continuously growing, significantly outpacing the growth rate of production of steel, copper, lead, and zinc.

List of used literature

1. V.A. Rabinovich, Z.Ya. Khavin "A short chemical reference book"

2. L.S. Guzey "Lectures on general chemistry"

3. N.S. Akhmetov “General and inorganic chemistry”

4. B.V. Nekrasov “Textbook of General Chemistry”

5. N.L. Glinka “General Chemistry”

One of the most common elements on the planet is aluminum. Physical and chemical properties aluminum are used in industry. You will find everything you need to know about this metal in our article.

Atomic structure

Aluminum is the 13th element of the periodic table. It is in the third period, group III, the main subgroup.

The properties and uses of aluminum are related to its electronic structure. The aluminum atom has a positively charged nucleus (+13) and 13 negatively charged electrons, located at three energy levels. The electronic configuration of the atom is 1s 2 2s 2 2p 6 3s 2 3p 1.

The outer energy level contains three electrons, which determine the constant valence of III. In reactions with substances, aluminum goes into an excited state and is able to give up all three electrons, forming covalent bonds. Like other active metals, aluminum is a powerful reducing agent.

Rice. 1. Structure of the aluminum atom.

Aluminum is an amphoteric metal that forms amphoteric oxides and hydroxides. Depending on the conditions, the compounds exhibit acidic or basic properties.

Physical Description

Aluminum has:

• lightness (density 2.7 g/cm 3);
• silver-gray color;
• high electrical conductivity;
• malleability;
• plasticity;
• melting point - 658°C;
• boiling point - 2518.8°C.

Tin containers, foil, wire, and alloys are made from metal. Aluminum is used in the manufacture of microcircuits, mirrors, and composite materials.

Rice. 2. Tin containers.

Aluminum is paramagnetic. Metal is attracted by a magnet only in the presence magnetic field.

Chemical properties

In air, aluminum quickly oxidizes, becoming covered with an oxide film. It protects the metal from corrosion and also prevents interaction with concentrated acids (nitric, sulfuric). Therefore, acids are stored and transported in aluminum containers.

Under normal conditions, reactions with aluminum are possible only after removing the oxide film. Most reactions occur at high temperatures.

The main chemical properties of the element are described in the table.

Aluminum does not react directly with hydrogen. Reaction with water is possible after removing the oxide film.

Rice. 3. Reaction of aluminum with water.

What have we learned?

Aluminum is an amphoteric active metal with constant valency. It has low density, high electrical conductivity, and plasticity. Attracted by a magnet only in the presence of a magnetic field. Aluminum reacts with oxygen, forming a protective film that prevents reactions with water, concentrated nitric and sulfuric acids. When heated, it reacts with non-metals and concentrated acids, and under normal conditions - with halogens and dilute acids. In oxides it displaces less active metals. Does not react with hydrogen.

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Metals are easy-to-process materials, and the leader among them is aluminum, the chemical properties of which have long been known to people. This metal, due to its characteristics, is widely used in everyday life, and almost everyone can find an aluminum product at home. It is necessary to consider in detail the properties of this metal as an element and as a simple substance.

How aluminum was discovered

Since ancient times, people have used potassium alum, an aluminum compound that can impart strength and stability to fabrics and skin. This property of the metal found its application in leatherworking: with the help of aluminum-potassium alum, furriers tanned leather, giving it strength and stability. The fact that aluminum oxide is present in nature in pure form, people learned only in the second half of the 18th century, but in those days they had not yet learned how to obtain a pure substance.

This was first achieved by Hans Christian Oersted, who treated the salt with potassium amalgam, then isolating powder from the resulting mixture gray. Thus, this chemical reaction helped me get a clean one. At the same time, such characteristics of the metal as high reducing ability and strong activity were established.

Interaction with oxides the reaction of replacing metal atoms in the oxide with aluminum allows one to obtain a large amount of heat and a new metal in free form.

Interaction with salts, namely with solutions of some less active salts.

Interaction with alkalis: due to strong interaction with alkali solutions, their solutions cannot be stored in aluminum containers.

Aluminothermy- the process of reducing metals, alloys and non-metals by exposing their oxides to metallic aluminum. Thanks to this feature of aluminum, metallurgists can mine such refractory metals as molybdenum, tungsten, zirconium, and vanadium.

Physical properties of aluminum as a simple substance

As a simple substance, aluminum is a silver-colored metal. It is capable of oxidizing in air, becoming covered with a dense oxide film.

This feature of the metal ensures its high resistance to corrosion. This property of aluminum, along with other characteristics, makes it an extremely popular metal, widely used in everyday life. In addition, aluminum is lightweight while maintaining high strength and ductility.

Not everyone known to people a substance has a set of similar characteristics.

Physical properties of aluminum

Aluminum is a ductile and malleable metal, used to make the thinnest foil; wire is rolled from aluminum.

The boiling point of the metal is 2518 °C.

The melting point of aluminum is 660 °C.

The density of aluminum is 2.7 g/cm³.

The widespread use of aluminum in areas of life is due to its chemical and physical properties.

Aluminum and its compounds

The main subgroup of group III of the periodic table 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,

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).

Metals are one of the most convenient materials to process. They also have their own leaders. For example, the basic properties of aluminum have been known to people for a long time. They are so suitable for everyday use that this metal has become very popular. What are both a simple substance and an atom, we will consider in this article.

History of the discovery of aluminum

For a long time, man has known the compound of the metal in question - it was used as a means that could swell and bind together the components of the mixture; this was also necessary in the manufacture of leather products. The existence of aluminum oxide in its pure form became known in the 18th century, in its second half. However, it was not received.

The scientist H. K. Ørsted was the first to isolate the metal from its chloride. It was he who treated the salt with potassium amalgam and isolated gray powder from the mixture, which was aluminum in its pure form.

Then it became clear that the chemical properties of aluminum are manifested in its high activity and strong reducing ability. Therefore, no one else worked with him for a long time.

However, in 1854, the Frenchman Deville was able to obtain metal ingots by electrolysis of the melt. This method is still relevant today. Especially mass production of valuable material began in the 20th century, when the problems of generating large amounts of electricity in enterprises were solved.

Today, this metal is one of the most popular and used in construction and the household industry.

General characteristics of the aluminum atom

If we characterize the element in question by its position in the periodic table, then several points can be distinguished.

1. Serial number - 13.
2. Located in the third small period, third group, main subgroup.
3. Atomic mass - 26.98.
4. The number of valence electrons is 3.
5. The configuration of the outer layer is expressed by the formula 3s 2 3p 1.
6. The element name is aluminum.
7. strongly expressed.
8. It has no isotopes in nature; it exists only in one form, with a mass number of 27.
9. The chemical symbol is AL, read as “aluminum” in formulas.
10. The oxidation state is one, equal to +3.

The chemical properties of aluminum are fully confirmed by the electronic structure of its atom, because having a large atomic radius and low electron affinity, it is capable of acting as a strong reducing agent, like all active metals.

Aluminum as a simple substance: physical properties

If we talk about aluminum as a simple substance, then it is a silvery-white shiny metal. In air it quickly oxidizes and becomes covered with a dense oxide film. The same thing happens when exposed to concentrated acids.

The presence of such a feature makes products made of this metal resistant to corrosion, which, naturally, is very convenient for people. That is why aluminum is so widely used in construction. They are also interesting because this metal is very light, yet durable and soft. The combination of such characteristics is not available to every substance.

There are several basic physical properties that are characteristic of aluminum.

1. High degree of malleability and ductility. Light, strong and very thin foil is made from this metal, and it is also rolled into wire.
2. Melting point - 660 0 C.
3. Boiling point - 2450 0 C.
4. Density - 2.7 g/cm3.
5. The crystal lattice is volumetric face-centered, metal.
6. Type of connection - metal.

The physical and chemical properties of aluminum determine the areas of its application and use. If we talk about everyday aspects, then the characteristics we have already discussed above play a big role. As a lightweight, durable and anti-corrosion metal, aluminum is used in aircraft and shipbuilding. Therefore, these properties are very important to know.

Chemical properties of aluminum

From a chemical point of view, the metal in question is a strong reducing agent that is capable of exhibiting high chemical activity while being a pure substance. The main thing is to remove the oxide film. In this case, activity increases sharply.

The chemical properties of aluminum as a simple substance are determined by its ability to react with:

• acids;
• alkalis;
• halogens;
• sulfur.

It does not interact with water under normal conditions. In this case, of the halogens, without heating, it reacts only with iodine. Other reactions require temperature.

Examples can be given to illustrate the chemical properties of aluminum. Equations of reactions of interaction with:

• acids- AL + HCL = AlCL 3 + H 2;
• alkalis- 2Al + 6H 2 O + 2NaOH = Na + 3H 2;
• halogens- AL + Hal = ALHal 3 ;
• gray- 2AL + 3S = AL 2 S 3.

In general, the most important property of the substance in question is its high ability to restore other elements from their compounds.

Regenerative capacity

The reducing properties of aluminum are clearly visible in the reactions of interaction with oxides of other metals. It easily extracts them from the composition of the substance and allows them to exist in a simple form. For example: Cr 2 O 3 + AL = AL 2 O 3 + Cr.

In metallurgy, there is a whole method for producing substances based on similar reactions. It is called aluminothermy. Therefore, in the chemical industry this element is used specifically for the production of other metals.

Distribution in nature

In terms of prevalence among other metal elements, aluminum ranks first. It is contained in the earth's crust 8.8%. If we compare it with non-metals, then its place will be third, after oxygen and silicon.

Due to its high chemical activity, it is not found in pure form, but only as part of various compounds. For example, there are many known ores, minerals, and rocks that contain aluminum. However, it is extracted only from bauxite, the content of which in nature is not very high.

The most common substances containing the metal in question:

• feldspars;
• bauxite;
• granites;
• silica;
• aluminosilicates;
• basalts and others.

In small quantities, aluminum is necessarily found in the cells of living organisms. Some species of club mosses and marine inhabitants are capable of accumulating this element inside their bodies throughout their lives.

Receipt

The physical and chemical properties of aluminum make it possible to obtain it only in one way: by electrolysis of a melt of the corresponding oxide. However, this process is technologically complex. The melting point of AL 2 O 3 exceeds 2000 0 C. Because of this, it cannot be subjected to electrolysis directly. Therefore, proceed as follows.

The product yield is 99.7%. However, it is possible to obtain even purer metal, which is used for technical purposes.

Application

The mechanical properties of aluminum are not so good that it can be used in its pure form. Therefore, alloys based on this substance are most often used. There are many of these, you can name the most basic ones.

1. Duralumin.
2. Aluminum-manganese.
3. Aluminum-magnesium.
4. Aluminum-copper.
5. Silumins.
6. Avial.

Their main difference is, naturally, third-party additives. All of them are based on aluminum. Other metals make the material more durable, corrosion-resistant, wear-resistant and easy to process.

There are several main areas of application of aluminum, both in pure form and in the form of its compounds (alloys).

Together with iron and its alloys, aluminum is the most important metal. It was these two representatives of the periodic table that found the most extensive industrial application in human hands.

Properties of aluminum hydroxide

Hydroxide is the most common compound that aluminum forms. Its chemical properties are the same as those of the metal itself - it is amphoteric. This means that it is capable of exhibiting a dual nature, reacting with both acids and alkalis.

Aluminum hydroxide itself is a white gelatinous precipitate. It is easily obtained by reacting an aluminum salt with an alkali or by reacting with acids, this hydroxide gives the usual corresponding salt and water. If the reaction occurs with an alkali, then hydroxo complexes of aluminum are formed, in which its coordination number is 4. Example: Na - sodium tetrahydroxoaluminate.