Characteristic of aluminum as a chemical element. Chemical and physical properties of aluminum. Physical properties of aluminum hydroxide

Properties 13 Al.

Atomic mass	26,98	clark, at.% (Commonness in nature)	5,5
Electronic configuration *		State of aggregation (n. u.).	solid
	0,143	Color	silver-white
	0,057		695
Ionization energy	5,98		2447
Relative electronegate	1,5	Density	2,698
Possible degrees of oxidation	1, +2,+3	Standard electrode potential	1,69

* The configuration of the external electronic levels of the element atom is given. The configuration of the remaining electronic levels coincides with that for the noble gas that the previous period and the above mentioned in brackets.

Aluminum - The main representative of metals of the main subgroup III of the periodic system. Properties of its analogues - gallium, India and tallina - Largely resemble the properties of aluminum, since all these elements have the same e-level configuration nS 2 NP 1 And therefore, they all show the degree of oxidation 3+.

Physical properties.Aluminum - Silver-White Metal Holding high heat and electrical conductivity. The surface of the metal is coated with thin, but very durable film of aluminum ol 2 ooz.

Chemical properties.Aluminum is very active if there is no protective film AL 2 Oz. This film prevents aluminum interaction with water. If you remove the protective film with a chemical method (for example, a solution of alkali), then the metal begins to vigorously interact with water with hydrogen release:

Aluminum in the form of chips or powder burns brightly in air, highlighting a large amount of energy:

This feature of aluminum is widely used to obtain different metal oxide metals by restoring aluminum. The method was called alumemith . Alumenum can only be obtained by those metals in which the heat of the formation of oxides is less than the heat of the formation of AL 2 OZ, for example:

When heating aluminum reacts with gray, nitrogen and carbon halogens, forming it, respectively haloenides:

Sulfide and aluminum carbide are completely hydrolyzed by the formation of aluminum hydroxide and respectively hydrogen sulfide and methane.

Aluminum is easily dissolved in hydrochloric acid of any concentration:

Concentrated sulfuric and nitric acids in the cold do not act on aluminum (passivated). For heating Aluminum is able to restore these acids without highlighting hydrogen:

IN diluted Sulfuric acid aluminum dissolves with hydrogen release:

IN diluted Nitric acid reaction comes with nitrogen oxide release (II):

Aluminum dissolves in alkali alkali metal carbonate solutions to form tetrahydroxyaluluminates:

Aluminium oxide. Al 2 O 3 has 9 crystalline modifications. The most common A is a modification. It is most chemically inert, based on it is grown by single-crystals of various stones for use from jewelry and technology.

In the laboratory, aluminum oxide is obtained by burning aluminum powder in oxygen or calcining its hydroxide:

Aluminum oxide, being amphoter can react not only with acids, but also with alkalis, as well as when fusing with alkali metal carbonates, giving metaluminda:

and with sour salts:

Aluminum hydroxide - White chatty substance, practically insoluble in water, possessing amphoteric properties. Aluminum hydroxide can be obtained by treating aluminum salts by alkalis or ammonium hydroxide. In the first case, an excess of alkali should be avoided, since otherwise aluminum hydroxide is dissolved with the formation of complex tetrahydroxyaluluminates [Al (he) 4] `:

In fact, in the last reaction are formed tetrahydroxodiacvaluminate ions`However, to record reactions usually use a simplified form [AL (OH) 4]`. With a weak acidification, tetrahydroxalulums are destroyed:

Aluminum salts. Aluminum hydroxide can be obtained from almost all aluminum salts. Almost all aluminum salts and strong acids are well soluble in water and at the same time strongly hydrolyzed.

Aluminum halides are well soluble in water, and in their structure are dimers:

2AlCl 3 є Al 2 Cl 6

Aluminum sulfates are easy, like all its salts, hydrolyzed:

Kalyasy aluminum alums are also known: KAL (SO 4) 2h 12H 2 O.

Acetate Aluminum Al (CH 3 COO) 3 Used in medicine as a mission.

Aluminosilicates.In nature, aluminum is found in the form of compounds with oxygen and silicon - aluminosilicates. Common formulas: (Na, k) 2 Al 2 Si 2 O 8 -Nfelin.

Also natural aluminum compounds are: Al 2 O 3 - Corundum, alumina; and compounds with shaft formulas Al 2 O 3 h NH 2 O and Al (OH) 3h NH 2 O - Boxites.

Getting. Aluminum is obtained by Al 2 O 3 melt electrolysis.

Definition

Aluminum Located in the third period, the III group of the main (a) subgroup of the periodic table. This is the first P-element of the 3rd period.

Metal. Designation - Al. Sequer number - 13. Relative atomic mass - 26.981 A.E.M.

Electronic structure of an aluminum atom

Aluminum atom consists of a positively charged kernel (+13), inside of which 13 protons and 14 neutrons are located. The kernel is surrounded by three shells, according to which 13 electrons are moving.

Fig. 1. A schematic representation of the structure of an aluminum atom.

The distribution of electrons by orbitals is as follows:

13Al) 2) 8) 3;

1s. 2 2s. 2 2p. 6 3s. 2 3p. 1 .

At the external energy level of aluminum there are three electrons, all electrons of the 3rd sublevel. The energy diagram takes the following form:

Theoretically, an excited state for an aluminum atom due to vacant 3 d.-Ibed. However, sparking electrons 3 s.- Affairs does not actually happen.

Examples of solving problems

Example 1.

Obtaining alumokalia kvasssov

Aluminum (Lat. Aluminium), - in the periodic system aluminum is in the third period, in the main subgroup of the Third Group. The charge of the core +13. Electronic structure of 1S 2 2S 2 2P 6 3S 2 3P 1 atom 1. Metal atomic radius 0.143 nm, covalent - 0.126 nm, conventional radius of Al 3+ ion - 0.057 nm. Al - Al + 5.99 ionization energy.

The most characteristic degree of oxidation of the aluminum atom is +3. The negative degree of oxidation is rarely manifested. In the outer electronic layer of the atom there are free D-lints. Due to this, its coordination number in compounds can be equal not only to 4 (ALCL 4-, ALH 4-, aluminosilicates), but also 6 (Al 2 O 3, 3+).

Historical reference. The name of aluminum comes from the lat. Alumen - so another 500 years BC Aluminum alums were called, which were used as a rubbish when the tissue is painted and for tossing the skin. Danish scientist X. K. Ersted in 1825, acting by Amalgam Potassium on anhydrous ALSL 3 and then driven by mercury, received relatively pure aluminum. The first industrial method of production of aluminum offered in 1854 French chemist A.E. Saint-Claire Devil: The method was to restore double aluminum chloride and sodium Na 3 AlCl 6 metal sodium. Similar in color on silver, aluminum at first was valued very expensive. From 1855 to 1890, only 200 tons of aluminum were obtained. A modern method for obtaining aluminum by electrolysis of the cryolito-cellular melt was developed in 1886 at the same time and independently of each other C. Hall in the United States and P. Era in France.

Finding in nature

Aluminum is the most common metal in the earth's crust. It accounts for 5.5-6.6 mol. Shares% or 8 wt.%. The main mass of it is concentrated in aluminosilicates. The extremely common product of the destruction of the solid rocks formed by them is clay, the main composition of which corresponds to the formula Al 2 O 3. 2SIO 2. 2H 2 O. From other natural forms of finding aluminum, bauxite Al 2 O 3 have the greatest value. XH 2 O and Minerals Corund Al 2 O 3 and Criched Alf 3. 3NAF.

Obtaining

Currently, aluminum industry is obtained by electrolysis of Al 2 O 3 alumina solution in molten cryolite. Al 2 O 3 should be clean enough, because impurities are removed from the glued aluminum. The melting point Al 2 O 3 is about 2050 ° C, and the cryolitis - 1100 o C. Electrolysis is subjected to a molten mixture of cryolya and Al 2 O 3, containing about 10 wt.% Al 2 O 3, which melts at 960 ° C and has electrical conductivity , density and viscosity, most favorable process. When adding ALF 3, CAF 2 and MGF 2, the electrolysis is possible at 950 o C.

Electrolyzer for aluminum smelting is an iron casing, laid out from the inside with refractory brick. Its bottom (under), assembled from blocks of compressed coal, serves as a cathode. Anodes are located on top: these are aluminum frames filled with coal briquettes.

Al 2 O 3 \u003d Al 3+ + ALO 3 3-

On the cathode, liquid aluminum is distinguished:

Al 3+ + 3e - \u003d Al

Aluminum is going to the bottom of the furnace, from where it is periodically produced. Oxygen is released on the anode:

4alo 3 3- - 12E - \u003d 2AL 2 O 3 + 3O 2

Oxygen oxidizes graphite to carbon oxides. As carbon is combustion, the anode is increasing.

Aluminum, in addition, is used as a doping additive to many alloys to give them a heat resistance.

Physical properties of aluminum. Aluminum combines a very valuable complex of properties: low density, high thermal conductivity and electrical conductivity, high plasticity and good corrosion resistance. It is easily forging, stamping, rolling, drawing. Aluminum is well welded with gas, contact and other welding types. Aluminum grille Cubic grazentized with parameter A \u003d 4,0413 Å. The properties of aluminum, like all metals, to mean degrees depend on its purity. Special purity aluminum properties (99.996%): density (at 20 ° C) 2698.9 kg / m 3; T pl 660.24 ° C; t of instrumentation about 2500 ° C; thermal expansion coefficient (from 20 ° to 100 ° C) 23.86 · 10 -6; thermal conductivity (at 190 ° C) 343 W / m · K, specific heat capacity (at 100 ° C) 931.98 j / kg · k. ; Electrical conductivity with respect to copper (at 20 ° C) 65.5%. Aluminum has low strength (strength of 50-60 MN / m 2), hardness (170 MN / m 2 for brinell) and high plasticity (up to 50%). With cold rolling, the strength of aluminum increases to 115 MN / m 2, the hardness is up to 270 MN / m 2, the relative elongation is reduced to 5% (1 MN / m 2 ~ and 0.1 kgf / mm 2). Aluminum is well polished, anodized and has a high reflectivity close to silver (it reflects up to 90% of incident light energy). With a large affinity for oxygen, aluminum in the air is covered with a thin, but very durable film of Al 2 oxide, protecting the metal from further oxidation and leads its high anti-corrosion properties. The strength of the oxide film and the protective effect of it is strongly decreasing in the presence of mercury impurities, sodium, magnesium, copper, and other aluminum struts to the action of atmospheric corrosion, sea and fresh water, practically does not interact with concentrated or strongly diluted nitric acid, with organic acids, food Products.

Chemical properties

When influencing finely fragmented aluminum, he is vigorously burning in the air. Similarly proceeds and interaction with gray. With chlorine and bromo, the compound occurs already at normal temperature, with iodom - when heated. At very high temperatures, aluminum is directly connected also with nitrogen and carbon. On the contrary, it does not interact with hydrogen.

In relation to water, aluminum is quite stable. But if a mechanical path or amalgaming, remove the protective effect of the oxide film, then an energetic reaction occurs:

Strongly diluted, as well as very concentrated HnO3 and H2SO4 on aluminum almost do not act (on cold), whereas with the average concentrations of these acids it gradually dissolves. Pure aluminum is rather stable and in relation to hydrochloric acid, but the usual technical metal dissolves in it.

Under action on aluminum aqueous solutions, the alkali of the oxide layer is dissolved, and aluminates are formed - salts containing aluminum as part of anion:

Al 2 O 3 + 2NAOH + 3H 2 O \u003d 2NA

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

2AL + 6H 2 O \u003d 2AL (OH) 3 + 3H 2

The forms of aluminum hydroxide reacts with an excess of alkali, forming hydroxyalulum:

Al (OH) 3 + NaOH \u003d Na

The total dissolution of aluminum dissolution in an aqueous solution of alkali:

2AL + 2NAOH + 6H 2 O \u003d 2NA + 3H 2

Aluminum is significantly dissolved in solutions of salts, which are due to their hydrolysis with an acidic or alkaline reaction, for example, in a solution of Na 2 CO 3.

In a row of stresses, it is located between Mg and Zn. In all its stable compounds aluminum trivalent.

The compound of aluminum with oxygen is accompanied by huge heat release (1676 kJ / mol Al 2 O 3), much greater than in many other metals. In view of this, when the mixture of the oxide of the corresponding metal with the aluminum powder, a violent reaction occurs, leading to the release of the free metal from the blood oxide. The recovery method using Al (altertermia) is often used to obtain a number of elements (Cr, Mn, V, W, etc.) in the free state.

Alumethemia sometimes use for welding of individual steel parts, in the hour of tram rails. The mixture used ("Termit") is usually made of thin aluminum and Fe 3 O 4 powders. It is set down with the smell of Al and Bao 2 mixture. The main reaction is due to the equation:

8Al + 3Fe 3 O 4 \u003d 4Al 2 O 3 + 9Fe + 3350 kJ

Moreover, the temperature is developing about 3000 o C.

Aluminum oxide is a white, very refractory (T. pl. 2050 o C) and insoluble in water mass. Natural Al 2 O 3 (Mineral Corundum), as well as the resulting artificially and then strongly calcined is characterized by a large hardness and non-solubility in acids. In the soluble state of Al 2 O 3 (T.N. alumina) can be transferred by alkalis.

Usually contaminated with iron oxide Natural Corundum due to its extreme hardness used for the manufacture of grinding circles, bars, etc. In a finely crushed form, it called the emery to clean the metal surfaces and the manufacture of sandpaper. For the same purposes often use Al 2 O 3, obtained by fusion of bauxite (the technical name - Alund).

Transparent painted corundum crystals - red ruby \u200b\u200b- chromium admixture - 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 of accurate devices, stones in hours, etc. Rubins crystals containing a small admixture of CR 2 O 3 are used as quantum generators - lasers creating a directed beam of monochromatic radiation.

Due to the insoluability of Al 2 O 3 in water, the al (OH) 3 hydroxide corresponding to this oxide can be obtained only by indirectly from salts. Preparation of hydroxide can be represented as the following scheme. Under action by alkali ions OH - gradually replaced in the aquocomplexes of 3+ water molecules:

3+ + OH - \u003d 2+ + H 2 O

2+ + OH - \u003d + + H 2 O

Oh - \u003d 0 + H 2 O

Al (OH) 3 is a bulk-colored sediment of white color, practically insoluble in water, but easily soluble in acids and strong alkalis. It has, consequently, amphoteric character. However, its main and particularly acidic properties are pronounced pretty weak. In excess NH 4 OH, aluminum hydroxide insoluble. One of the forms of dehydrated hydroxide - alumino is used in the technique as an adsorbent.

When interacting with strong alkalis, appropriate aluminates are formed:

NaOH + Al (OH) 3 \u003d Na

The aluminates of the most active monovalent metals in water are well soluble, but due to strong hydrolysis, their solutions are stable only if there is sufficient excess alkali. Aluminates, produced from weaker bases, hydrolyzed in the solution almost aimed and therefore can be obtained only by dry path (al 2 o 3 fusion with appropriate metals oxides). Metalulumages are formed, in its composition producing Halo 2 from metaaluminic acid. Most of them are insoluble in water.

Al (OH) 3 acids forms salts. The derivatives of most strong acids are well soluble in water, but rather significantly hydrolyzed, and therefore their solutions show the acidic reaction. Also more hydrolyzed soluble salts of aluminum and weak acids. Due to hydrolysis sulphide, carbonate, cyanide and some other salts of aluminum from aqueous solutions, it cannot be obtained.

In the aqueous medium, 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 \u003d 2+ + OH 3 +

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

Aluminosilicates can be considered as silicates in which part of SiO 4 4 silician tetrahedra is replaced with ALO 4 aluminoisologenic tetrahedra 5- from aluminosilicates, field splams are most common, which account for more than half of the mass of the earth's crust. Their main representatives - Minerals

orthoclases K 2 Al 2 Si 6 O 16 or K 2 O. Al 2 O 3. 6Sio 2.

albit Na 2 Al 2 Si 6 O 16 or Na 2 O. Al 2 O 3. 6Sio 2.

help Caal 2 Si 2 O 8 or Cao. Al 2 O 3. 2SIO 2.

Minerals of the mica group are very common, such as Musk Kal 2 (ALSI 3 O 10) (OH) 2. Mineral nepheline (Na, K) 2, which is used to obtain alumina soda products and cement to obtain alumina. This production is made up of the following operations: a) Nefeline and limestone sach out in tubular furnaces at 1200 ° C:

(Na, k) 2 + 2Caco 3 \u003d 2Casio 3 + Naalo 2 + Kalo 2 + 2Co 2

b) the resulting mass is leached by water - the solution of sodium and potassium aluminates and the Casio 3 sludge is formed:

Naalo 2 + Kalo 2 + 4H 2 O \u003d Na + K

c) through a solution of aluminates are allowed formed during sintering CO 2:

Na + K + 2CO 2 \u003d NaHCO 3 + KHCO 3 + 2AL (OH) 3

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

2AL (OH) 3 \u003d Al 2 O 3 + 3H 2 O

e) the evaporation of the uterine solution is isolated soda and fogging, and the previously obtained sludge goes to the production of cement.

In the production of 1 T Al 2 O 3, 1 tons of coherent coherent are obtained.

Some aluminosilicates have a loose structure and are capable of ion exchange. Such silicates are natural and especially artificial - used for water treatment. In addition, due to its highly developed surface, they are used as carriers of catalysts, i.e. As materials impregnated with the catalyst.

Aluminum halides under normal conditions - colorless crystalline substances. Alf 3 aluminum halides are very different in properties from its analogues. It is refined, dissolved little in water, chemically inactive. The main method of obtaining Alf 3 is based on anhydrous HF action on Al 2 O 3 or Al:

AL 2 O 3 + 6HF \u003d 2ALF 3 + 3H 2 O

Aluminum compounds with chlorine, bromine and iodine of low-saline, are very reactive and well 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 an aqueous solution, all of them are strongly hydrolyzed, but in contrast to the typical acidic halides of non-metals, their hydrolysis is incomplete and reversible. Being noticeably volatile under normal conditions, AlCl 3, Alb 3 and Ali 3 smoke in humid air (due to hydrolysis). They can be obtained by direct interaction of simple substances.

ALCL 3, ALBR 3 and ALI 3 vapor density with relatively low temperatures more or less accurately correspond to doubled formulas - Al 2 Hal 6. The spatial structure of these molecules corresponds to two tetrahedra with a common edge. Each aluminum atom is associated with four halogen atoms, and each of the central halogen atoms with both aluminum atoms. Of the two bonds of the central halogen atom, one is donor-acceptor, and aluminum functions as an acceptor.

With halide salts of a number of monovalent metals of aluminum halides, complex compounds are formed, mainly types M 3 and M (where HAL is chlorine, bromine or iodine). The tendency to the reactions of attachment is generally expressed in the halides under consideration. It is precisely with this that the most important technical use of AlCl 3 as a catalyst (when processing oil and with organic synthesis) is connected.

From the fluoroollumats the greatest use (for the preparation of Al, F 2, enamel, glass, etc.) has a Na 3 cryolite. Industrial production of artificial cryolite is based on the processing of hydroxide of aluminum by hydrofluoric acid and soda:

2AL (OH) 3 + 12HF + 3NA 2 CO 3 \u003d 2NA 3 + 3CO 2 + 9H 2 O

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

Although aluminum is chemically interacting with hydrogen, aluminum hydride can be obtained indirectly. It is a white amorphous mass of the composition (ALH 3) N. Decomposes when heated above 105 ° C with hydrogen is released.

When Alh 3 interacts with the main hydrides in the ethereal solution, hydroaluminates are formed:

Lih + Alh 3 \u003d Li

Hydride aluminum - white solids. Water violently decomposed. They are strong reducing agents. Apply (especially Li) in organic synthesis.

Al 2 aluminum sulfate (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 when preparing some paper varieties.

Aluminum Kal alum Kal (SO 4) 2. 12H 2 O are used in large quantities for tanning leather, as well as in a crushing case as a dreache for cotton fabrics. In the latter case, the action of the alum is based on the fact that aluminum hydroxide hydroxyde resulting due to their hydrolysis is deposited in the fibers of the tissue in a fine state and, adsorbating the dye, firmly holds it on the fiber.

From the remaining aluminum derivatives, it is necessary to mention its acetate (otherwise - acetic acid salt) Al (CH 3 COO) 3, used when tissue collapse (as a hydraulic) and in medicine (gramcons and compresses). Aluminum nitrate is easily soluble in water. Aluminum phosphate insoluble in water and acetic acid, but soluble in strong acids and alkalis.

Aluminum in the body. Aluminum is part of animal and plant tissues; In the mammalian animals, 10 -3 to 10 -5% aluminum (raw substance) were 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 turnip), in animal products from 4 mg (honey) to 72 mg per 1 kg of dry matter (beef). In the daily basis of man, the aluminum content reaches 35-40 mg. The organisms are known - aluminum hubs, for example, frames (lycopodiaceae), containing in ashes to 5.3% aluminum, mollusks (Helix and Lithorina), in the asse of 0.2-0.8% aluminum. Forming insoluble compounds with phosphates, aluminum disrupts the power of plants (absorption of phosphates roots) and animals (phosphate absorption in the intestine).

Geochemistry Aluminum. The geochemical features of aluminum are determined by its greater affinity for oxygen (in minerals aluminum enters oxygen octahedra and tetrahedra), permanent valence (3), weak solubility of most natural compounds. In endogenous processes, when the magma is frozen and the formation of erupted rocks, aluminum is included in the crystal lattice of field spatts, mica and other minerals - aluminosilicates. In the biosphere aluminum - a weak migrant, it is not enough in the organisms and the hydrosphere. In a humid climate, where the decomposing residues of abundant vegetation form many organic acids, aluminum migrates in soils and waters in the form of organicineral colloidal compounds; Aluminum is adsorbed by colloids and deposited at the bottom of the soil. Aluminum connection with silicon is partially broken and places in the tropics are formed minerals - aluminum hydroxides - Bleit, diaspora, hydraulic. The larger part of the aluminum is part of aluminosilicates - kaolinitis, bidelite and other clay minerals. Weak mobility determines the residual accumulation of aluminum in the crust of the weft tropics. As a result, eluvial bauxites are formed. In past geological epochs, bauxite was also accumulated in the lakes and the coastal zone of the seas of tropical areas (for example, sedimentary bauxes of Kazakhstan). In the steppes and deserts, where there is little living substance, and the water is neutral and alkaline, aluminum almost does not migrate. The most energetic migration of aluminum in volcanic areas, where strong river and groundwater rich in aluminum are observed. In places of bias of acidic water with alkaline - sea (in the mouths of rivers and others), aluminum is deposited with the formation of bauxite deposits.

Aluminum application. 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 from other metals. In electrical engineering, aluminum successfully replaces copper, especially in the production of massive conductors, for example, in air lines, high-voltage cables, distribution device tires, transformers (electrical conductivity of aluminum reaches 65.5% of the electrical conductivity of copper, and it is more than three times easier than copper; With a cross section, providing the same conductivity, the mass of wires from aluminum twice as much copper). Ultrapure aluminum is used in the production of electrical capacitors and rectifiers, the action of which is based on the ability of aluminum oxide film to skip electrical current in one direction. Ultrachoft 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 kinds of mirror reflectors. High purity aluminum is used to prevent metal surfaces from the action of atmospheric corrosion (plating, aluminum paint). Possessing a relatively low cross section of neutron absorption, aluminum is used as structural material in nuclear reactors.

In aluminum tanks, a large container is stored and transported liquid gases (methane, oxygen, hydrogen, etc.), nitrogen and acetic acid, clean water, hydrogen peroxide and dietary oils. Aluminum is widely used in the equipment and apparatus of the food industry, for packaging food products (in the form of foil), for the production of different kinds of household products. Consumption of aluminum for finishing buildings, architectural, transport and sports facilities increased dramatically.

In aluminum metallurgy (in addition to alloys on its basis), one of the most common alloying additives in alloys based on Cu, Mg, Ti, Ni, Zn and Fe. Aluminum is also used to deoxine steel before pouring it into shape, as well as in the processes of obtaining some metals by aluminothermia. Based on aluminum by powder metallurgy, a SAP (sintered aluminum powder) has been created with temperatures above 300 ° with great heat resistance.

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

The production and consumption of aluminum is continuously growing, significantly ahead of the production of steel, copper, lead, zinc.

List of used literature

1. V.A. Rabinovich, Z.Ya. Havin "Short Chemical Directory"

2. L.S. Guise "Lectures for General Chemistry"

3. N.S. Akhmetov "General and inorganic Chemistry"

4. B.V. Nekrasov "Tutorial of General Chemistry"

5. N.L. Glinka "General Chemistry"

Aluminum - element of the 13th group of the periodic table of chemical elements, the third period, with atomic number 13. refers to the group of light metals. The most common metal and the third prevalence is the chemical element in the earth's crust (after oxygen and silicon).

A simple aluminum substance is a light, paramagnetic metal of silver-protein, easy to form molding, casting, mechanical processing. Aluminum has a high heat-energy resistance, resistance to corrosion due to the rapid formation of durable oxide films that protect the surface from further interaction.

Modern method of obtaining, Hall-Era process. It consists in dissolving Al2O3 aluminum oxide in the Na3AlF6 cryolite melt, followed by electrolysis using consumable coke orgrafic anode electrodes. This method of obtaining requires very large costs of electricity, and therefore received industrial applications only in the 20th century.

Laboratory method for producing aluminum: restoration of the metal potassium of anhydrous aluminum chloride (the reaction occurs when heated without air access):

Metal silver-white, light, density - 2.7 g / cm³, melting point in technical aluminum - 658 ° C, at high purity aluminum - 660 ° C, high plasticity: technical - 35%, in pure - 50% , rolled into a slim sheet and even foil. Aluminum has high electrical conductivity (37 · 106 cm / m) and thermal conductivity (203.5 W / (M · K)), 65%, has a high reflectivity.

Aluminum forms alloys with almost all metals. The most famous alloys with copper and magnesium (duralumin) and silicon (silumin).

According to the prevalence in the earth's crust of the Earth, it takes the 1st place among metals and 3rd place among the elements, yielding only oxygen and silicon. The mass concentration of aluminum in the earth's crust according to various researchers is estimated from 7.45 to 8.14%. In nature, aluminum, due to high chemical activity, occurs almost exclusively in the form of compounds.

Natural aluminum consists almost entirely of a single stable isotope 27Al with insignificant trails 26Al, the most long-lived radioactive isotope with a half-life of 720 thousand years generated in an atmosphere when cleavage of argon nuclei 40Ar protons of cosmic rays with high energies.

Under normal conditions, aluminum is coated with thin and durable oxide film and therefore does not react with classical oxidizing agents: with H2O (T °), O2, HNO3 (without heating). Due to this, aluminum is practically not subject to corrosion and therefore is widely demanded by the modern industry. However, in the destruction of the oxide film (for example, in contact with solutions of ammonium salts NH4 +, hot alkalis or as a result of amalgaming), aluminum acts as an active reducing agent. It is possible to prevent the oxide film formation by adding such metals as gallium, indium or tin to aluminum. In this case, the surface of the aluminum is wetted with low-melting eutectic based on these metals.

Easily reacts with ordinary substances:

with oxygen, forming aluminum oxide:

with halogens (except fluoride), forming chloride, bromide or aluminum iodide:

with other non-metals reacts when heated:

with fluorine, forming aluminum fluoride:

with gray, forming aluminum sulphide:

with nitrogen, forming aluminum nitride:

with carbon, forming aluminum carbide:

Sulfide and aluminum carbide are completely hydrolyzed:

With complicated substances:

with water (after removal of the protective oxide film, for example, amalgaming or hot-sleeper solutions):

with alkalis (with the formation of tetrahydroxyaluminates and other aluminates):

Easily dissolved in hydrochloric and diluted sulfuric acids:

When heated, dissolves in acids - oxidizers forming soluble aluminum salts:

restores metals from their oxides (aluminothermia):

44. Aluminum compounds, their amphoteric properties

Electronic configuration of the external level of aluminum ... 3S23P1.

In the excited state, one of the S-electrons switches to the free cell of the P-suite, such a state corresponds to the valence of III and the degree of oxidation +3. In the outer electron layer of the aluminum atom there are free D-liners.

Essential Natural Connections - Aluminosilicates:

white clay Al2O3 ∙ 2SiO2 ∙ 2H2O, field spat K2O ∙ Al2O3 ∙ 6SiO2, mica K2O ∙ Al2O3 ∙ 6SiO2 ∙ H2O

Of other natural forms of aluminum finding, Boxites A12IZ ∙ NN2O, Corund A1foz minerals and a1fsis CHRITS ∙ 3NAF have the greatest value.

Lightweight, silver-white, plastic metal, perfectly conducts electric current and heat.

On the air aluminum is covered with the finest (0.00001 mm), but a very dense film of oxide, protecting the metal from further oxidation and a matte appearance.

Aluminum A12O3 oxide

White solid insoluble in water, melting point 20500С.

Natural A12O3 - Mineral Corundum. Transparent painted corundum crystals - red ruby \u200b\u200b- contains a chromium admixture - 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 of accurate devices, stones in hours, etc.

Chemical properties

Aluminum oxide shows amphoteric properties

1. Interaction with acids

A12O3 + 6HCl \u003d 2ALCl3 + 3H2O

2. Interaction with alkalis

A12O3 + 2NAOH - 2NAALO2 + H2O

Al2O3 + 2NAOH + 5H2O \u003d 2NA

3. When the mixture of the appropriate metal oxide with aluminum powder, a stormy reaction occurs, leading to the isolation of the free metal from the brushed oxide. Recovery method using Al (altertermia) is often used to obtain a number of elements (CR, MP, V, W, etc.) in a free state

2A1 + WO3 \u003d A12IZ + W

4. Interaction with salts having a strong widening environment due to hydrolysis

Al2O3 + Na2CO3 \u003d 2 Naalo2 + CO2

Aluminum A1 hydroxide (OH) 3

A1 (OH) 3 is a bulk puddle of white sediment, practically insoluble in water, but easily soluble in acids and strong alkalis. It has, consequently, amphoteric character.

Aluminum hydroxide is obtained with alumina soluble salts with alkalis

AlCl3 + 3NAOH \u003d Al (OH) 3 ↓ + 3NACL

Al3 + + 3oh- \u003d Al (OH) 3 ↓

This reaction can be used as high-quality ion Al3 +

Chemical properties

1. Interaction with acids

Al (OH) 3 + 3HCl \u003d 2AlCl3 + 3H2O

2. When interacting with strong alkalis, appropriate aluminates are formed:

NaOH + A1 (OH) s \u003d na

3. Thermal decomposition

2AL (OH) 3 \u003d Al2O3 + 3H2O

Salts aluminumIesighing hydrolysis in the cation, environment Space (pH< 7)

AL3 + + N + ON-↔LON2 + + H +

AL (NO3) 3 + H2O↔ ALOH (NO3) 2 + HNO3

The soluble salts of aluminum and weak acids are complete (irreversible hydrolysis)

AL2S3 + 3H2O \u003d 2AL (OH) 3 + 3H2S

Al2O3 alumina oxide is part of some antacid agents (for example, Almagel), used at elevated acidity of the gastric juice.

Kal (SO4) 3 12H2O - alumboy alums are used in medicine for the treatment of skin diseases, like hemostatic means. And also used as a tanning substance in the leather industry.

(CH3COO) 3Al - Liquid drilling - 8% Aluminum acetate solution has a binder and anti-inflammatory effect, in large concentrations has moderate antiseptic properties. It is used in a divided form for rinsing, lotions, with inflammatory diseases of the skin and mucous membranes.

AlCl3 is used as a catalyst in organic synthesis.

Al2 (SO4) 3 · 18 H20 - applied when cleaning water.

(A L), Gallium (GA), India (In) and Tallal (T L).

As can be seen from the given data, all these elements were opened inXIX century.

Opening of metals of the main subgroup III Groups

IN	Al	GA.	IN.	TL
1806	1825	1875	1863	1861
Utyvak,	G. Eirsted	L. De Baabodran	F.reich,	U.Kruk
L. Tenar	(Denmark)	(France)	I. Richter.	(England)
(France)			(Germany)

Bor is nonmetall. Aluminum - transition metal, and gallium, indium and thallium - full metal. Thus, with the increasing radii of atoms of elements of each group of periodic system, the metal properties of simple substances are enhanced.

In this lecture, we will consider the properties of aluminum.

1. The position of aluminum in Table D. I. Mendeleev. The structure of the atom, manifestable oxidation degrees.

Aluminum element is located inIII Group, main "A" subgroup, 3 periodic system, sequence number 17, relative atomic massAr (al. ) \u003d 27. His neighbor on the left in the table is magnesium - typical metal, and on the right - silicon - already non-metal. Consequently, aluminum should show the properties of some intermediate nature and its compounds are amphoteric.

Al +13) 2) 8) 3, p - element,

Basic condition 1S 2 2S 2 2P 6 3S 2 3P 1
Excited state 1S 2 2S 2 2P 6 3S 1 3P 2

Aluminum exhibits in compounds the degree of oxidation +3:

Al 0 - 3 E - → Al +3

2. Physical properties

Aluminum in free form - silver-white metal with high heat and electrical conductivity.Melting point650 o C. Aluminum has a low density (2.7 g / cm 3) - approximately three times less than that of iron or copper, and at the same time is a durable metal.

3. Finding in nature

In the prevalence in nature takes 1st among metals and 3rd place among elements, yielding only oxygen and silicon. The percentage of aluminum content in the earth's crust according to various researchers is from 7.45 to 8.14% of the mass of the earth's crust.

In nature, aluminum is found only in connections (minerals).

Some of them:

· Boxites - Al 2 O 3 H 2 O (with impurities SiO 2, Fe 2 O 3, Caco 3)

· Nefelina - KNA 3 4

· Alunites - Kal (SO 4) 2 2AL (OH) 3

· Alumors (Mixtures of kaolins with SiO 2 sand, Caco 3 limestone, MGCO 3 magnesite)

· Corundum - Al 2 O 3

· Field Spad (orthoclases) - K 2 O × Al 2 O 3 × 6sio 2

· Kaolinitis - Al 2 O 3 × 2Sio 2 × 2H 2 O

· Alunite - (Na, k) 2 SO 4 × Al 2 (SO 4) 3 × 4Al (OH) 3

· Beryl - 3Wo Al 2 O 3 6SIO 2

Bauxite
Al 2 O 3	Corundum
	Ruby
	Sapphire

4. Chemical properties of aluminum and its connections

Aluminum easily interacts with oxygen under normal conditions and is covered with an oxide film (it gives a matte appearance).

Demonstration of oxide film

Its thickness is 0.00001 mm, but thanks to it, aluminum does not corrosive. For the studies, the aluminum properties, the oxide film is removed. (With the help of sandpaper, or chemically: first dropping into a solution of alkali to remove an oxide film, and then into a solution of mercury salts for the formation of aluminum alloy with mercury - amalgams).

I.. Interaction with ordinary substances

Aluminum at room temperature is actively reacting with all halogens, forming halides. When heated, it interacts with sulfur (200 ° C), nitrogen (800 ° C), phosphorus (500 ° C) and carbon (2000 ° C), with iodine in the presence of a catalyst - water:

2a L + 3 S \u003d A L 2 S 3 (aluminum sulfide)

2a l + n 2 \u003d 2a ln (aluminum nitride)

A L + P \u003d A L P (aluminum phosphide),

4a L + 3C \u003d A L 4 C 3 (aluminum carbide).

2 oll +3 i 2 \u003d 2 a l I 3 (aluminum iodide) EXPERIENCE

All of these compounds are completely hydrolyzed to form aluminum hydroxide and, accordingly, hydrogen sulfide, ammonia, phosphine and methane:

Al 2 S 3 + 6H 2 O \u003d 2AL (OH) 3 + 3H 2 S

Al 4 C 3 + 12H 2 O \u003d 4Al (OH) 3 + 3CH 4

In the form of chips or powder, it burns brightly in the air, highlighting a large amount of heat:

4a L + 3 O 2 \u003d 2A L 2 O 3 + 1676 kJ.

Aluminum burning in air

EXPERIENCE

II.. Interaction with complex substances

Interaction with water :

2 AL + 6 H 2 O \u003d 2 AL (OH) 3 +3 H 2

without oxide film

EXPERIENCE

Interaction with metals oxides:

Aluminum is a good reducing agent, as it is one of the active metals. It is located in a number of activity immediately after alkaline earth metals. therefore restores metals from their oxides . Such a reaction is alylummia - used to obtain pure rare metals, such as tungsten, bathtubadium, etc.

3 FE 3 O 4 +8 Al \u003d 4 Al 2 O 3 +9 Fe +Q.

The thermite mixture of Fe 3 O 4 IAL (powder) is also used in thermal welding.

C R 2 O 3 + 2A L \u003d 2C R + A L 2 O 3

Interaction with acids :

With sulfuric acid solution: 2 Al + 3 H 2 SO 4 \u003d Al 2 (SO 4) 3 +3 H 2

With cold concentrated sulfur and nitric does not react (passivates). Therefore, nitric acid is transported in aluminum tanks. When heated aluminum is able to restore these acids without hydrogen release:

2a L + 6H 2 S o 4 (concluding) \u003d A L 2 (S O 4) 3 + 3 S O 2 + 6N 2 O,

A L + 6N NO 3 (concaten) \u003d A L (NO 3) 3 + 3 NO 2 + 3N 2 O.

Interaction with alkalis .

2 Al + 2 NaOH + 6 H 2 O \u003d 2 Na [ Al (OH) 4 ] +3 H 2.

EXPERIENCE

Na.[BUTl.(He) 4] – tetrahydroxalulum of sodium

At the suggestion of Chemist Gorbov, in the Russian-Japanese war, this reaction was used to produce hydrogen for balloons.

With salts solutions:

2 Al + 3 Cuso 4 \u003d Al 2 (SO 4) 3 + 3 Cu

If the surface of the aluminum is to lose the mercury salt, then the reaction occurs:

2 Al + 3 HGCL 2 = 2 Alcl 3 + 3 Hg.

The distinguished mercury dissolves aluminum, formaemalgam .

Aluminum ion detection in solutions : EXPERIENCE

5. Application of aluminum and its compounds

The physical and chemical properties of aluminum led to its widespread use in the technique. Large consumer Aluminum Aviation Industry: The airplane on 2/3 consists of aluminum and its alloys. The plane from the steel would be too heavy and could carry much less passengers. Therefore, aluminum is called a winged metal. Aluminum makes cables and wires: With the same electrical conductivity, their mass is 2 times less than the corresponding copper products.

Considering the corrosion resistance of aluminum, from it made the details of the devices and the container for nitric acid. Aluminum powder is the basis for the manufacture of silver paint to protect the iron products from corrosion, as well as for reflection of the heat rays, such paint covers the refinery, costumes of firefighters.

Aluminum oxide is used to obtain aluminum, as well as refractory material.

Aluminum hydroxide is the main component of all the known Maalox drugs, an almagel, which reduce the acidity of gastric juice.

Aluminum salts are strong-hydrolyzed. This property is used in the process of water purification. Aluminum sulfate is administered to the purified water and a small amount of hazed lime for neutralizing the resulting acid. As a result, the volumetric precipitate of aluminum hydroxide is isolated, which, settling, takes with rigorous particles of mud and bacteria.

Thus, aluminum sulfate is a coagulant.

6. Obtaining aluminum

1) A modern cost-effective method for producing aluminum was invented by the American Hall and French Era in 1886. It consists in electrolysis of aluminum oxide solution in molten cryolite. The molten cryiton Na 3 ALF 6 dissolves Al 2 O 3, as water dissolves sugar. The electrolysis of the "solution" of aluminum oxide in the molten cryolite occurs as if the cryith was only a solvent, and aluminum oxide - electrolyte.

2AL 2 O 3 EL → 4Al + 3O 2

In the English "Encyclopedia for boys and girls", an article about aluminum begins in the following words: "On February 23, 1886, a new metal century began in the history of civilization - a century of aluminum. On this day, Charles Hall, a 22-year-old chemist, appeared in the laboratory of his first teacher with a dozen little balls of silver-white aluminum in his hand and with the news that he found a way to make this metal cheap and large quantities. " So the Hall was made by the founder of the American aluminum industry and the Anglo-Saxon National Hero, as a person who made a magnificent business from science.

2) 2AL 2 O 3 +3 C \u003d 4 AL + 3 CO 2

IT IS INTERESTING:

• Metal aluminum was first allocated in 1825 Danish physicist Hans Christian Ersted. By skipping chlorine gas through a layer of hot aluminum oxide mixed with coal, Ersted allocated aluminum chloride without the slightest traces of moisture. To restore metal aluminum, Ersteda needed to treat aluminum chloride amalgam potassium. After 2 years, the German chemist Friedrich Völler. Improved method, replacing Calia's amalgam clean potassium.
• In 18-19 centuries, aluminum was the main jewelry metal. In 1889, D.I. Indeleev in London for merits in the development of chemistry was awarded a valuable gift - weights made of gold and aluminum.
• By 1855, the French scientist, Cleriary Deville developed a method for producing metal aluminum on technical scales. But the way was very expensive. Deville enjoyed the special patronage of Napoleoniiii, imperatorofrance. In the meaning of devotion and gratitude, Devil made Devilo for the son of Napoleon, a newborn prince, elegantly engraved rattage - the first "product of the stronghold" of aluminum. Napoleon intended to even equip his guards by aluminum pures, but the price turned out to be exorbitantly high. At that time, 1 kg of aluminum cost 1000 grades, i.e. 5 times more than silver. Only after the invention of the electrolytic process, aluminum was equal to conventional metals in its value.
• Do you know that aluminum, entering the human body, causes a disorder of the nervous system. After its excess, the metabolism is disturbed. And protective means is vitamin C, calcium compounds, zinc.
• When combustion of aluminum in oxygen and fluorine, a lot of heat is distinguished. Therefore, it is used as an additive to rocket fuel. Rocket "Saturn" burns during the flight 36 tons of aluminum powder. The idea of \u200b\u200busing metals as a component of rocket fuel was first expressed F. A. Zander.

Simulators

Simulator No. 1 - characteristic of aluminum on the position in the periodic system of elements D. I. Mendeleev

Simulator No. 2 - Aluminum reaction equations with simple and complex substances

Simulator No. 3 - Chemical properties of aluminum

Tasks for fixing

№1. To obtain aluminum from aluminum chloride as a reducing agent, a metal calcium can be used. Make the equation of this chemical reaction, characterize this process using an electronic balance.
Think! Why can this reaction be carried out in aqueous solution?

№2. Finish the chemical reaction equations:
Al + H 2 SO 4 (solution ) ->
Al + Cucl 2 -\u003e
Al + HNO 3 (end ) - T -\u003e
Al + NaOH + H 2 O -\u003e

Number 3. Transform:
Al -\u003e alcl 3 -\u003e al -\u003e al 2 s 3 -\u003e al (oh) 3 - t -\u003e al 2 o 3 -\u003e al

№4. Solve the task:
The alloy of aluminum and copper has been involved in an excess of the concentrated sodium hydroxide solution when heated. 2.24 liters of gas (N.O.) were released. Calculate the percentage of alloy if its total mass was 10 g?