Description of the chemical element aluminum according to the table. Characteristics of aluminum

DEFINITION

Aluminum located in the third period, group III of the main (A) subgroup of the Periodic table. This is the first p-element of the 3rd period.

Metal. Designation - Al. Serial number - 13. Relative atomic mass - 26.981 amu.

Electronic structure of the aluminum atom

The aluminum atom consists of a positively charged nucleus (+13), inside of which there are 13 protons and 14 neutrons. The nucleus is surrounded by three shells, through which 13 electrons move.

Rice. 1. Schematic representation of the structure of the aluminum atom.

The distribution of electrons among orbitals is as follows:

13Al) 2) 8) 3 ;

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

The outer energy level of aluminum contains three electrons, all electrons of the 3rd sublevel. The energy diagram takes the following form:

An excited state is theoretically possible for the aluminum atom due to the presence of a vacant 3 d-orbitals. However, electron pairing 3 s-sublevel does not actually occur.

Examples of problem solving

EXAMPLE 1

Lesson type. Combined.

Tasks:

Educational:

1. Update students’ knowledge about the structure of the atom, the physical meaning of the serial number, group number, period number using the example of aluminum.

2. To form in students the knowledge that aluminum in a free state has special, characteristic physical and chemical properties.

Educational:

1. To stimulate interest in the study of science by providing brief historical and scientific reports on the past, present and future of aluminum.

2. Continue to develop students’ research skills when working with literature and performing laboratory work.

3. Expand the concept of amphotericity by revealing the electronic structure of aluminum and the chemical properties of its compounds.

Educational:

1. Foster respect for the environment by providing information about the possible uses of aluminum yesterday, today, tomorrow.

2. Develop the ability to work as a team in each student, take into account the opinions of the entire group and defend theirs correctly when performing laboratory work.

3. Introduce students to the scientific ethics, honesty and integrity of natural scientists of the past, providing information about the struggle for the right to be the discoverer of aluminum.

REPEATING THE COVERED MATERIAL on the topics alkali and alkaline earth M (REPEAT):

What is the number of electrons in the outer energy level of alkali and alkaline earth M?

What products are formed when sodium or potassium reacts with oxygen? (peroxide), is lithium capable of producing peroxide in reaction with oxygen? (no, the reaction produces lithium oxide.)

How are sodium and potassium oxides obtained? (by calcination of peroxides with the corresponding Me, Pr: 2Na + Na 2 O 2 = 2Na 2 O).

Do alkali and alkaline earth metals exhibit negative oxidation states? (no, they don’t, since they are strong reducing agents.).

How does the radius of an atom change in the main subgroups (from top to bottom) of the Periodic System? (increases), what is this connected with? (with increasing number of energy levels).

Which of the groups of metals we have studied are lighter than water? (for alkaline ones).

Under what conditions does the formation of hydrides occur in alkaline earth metals? (at high temperatures).

Which substance, calcium or magnesium, reacts more actively with water? (calcium reacts more actively. Magnesium reacts actively with water only when it is heated to 100 0 C).

How does the solubility of alkaline earth metal hydroxides in water change in the series from calcium to barium? (water solubility increases).

Tell us about the features of storing alkali and alkaline earth metals, why are they stored this way? (since these metals are very reactive, they are stored in containers under a layer of kerosene).

CHECK WORK on the topics alkaline and alkaline earth M:

LESSON SUMMARY (NEW MATERIAL LEARNED):

Teacher: Hello guys, today we are moving on to the study of subgroup IIIA. List the elements located in subgroup IIIA?

Trainees: It includes elements such as boron, aluminum, gallium, indium and thallium.

Teacher: What number of electrons do they contain at the outer energy level, oxidation state?

Trainees: Three electrons, oxidation state +3, although thallium has a more stable oxidation state +1.

Teacher: The metallic properties of the elements of the boron subgroup are much less pronounced than those of the elements of the beryllium subgroup. Boron is non-M. Subsequently, within the subgroup, with increasing charge of the nucleus M, the properties intensify. Al– already M, but not typical. Its hydroxide has amphoteric properties.

Of the M of the main subgroup of group III, aluminum is of greatest importance, the properties of which we will study in detail. It is interesting to us because it is a transitional element.

Properties of 13 Al.

*The configuration of the external electronic levels of an element’s atom is shown. The configuration of the remaining electronic levels coincides with that of the noble gas that completes the previous period and is indicated in parentheses.

Aluminum- the main representative of the metals of the main subgroup of group III of the periodic table. Properties of its analogues - gallia, india And thallium - are in many ways reminiscent of the properties of aluminum, since all these elements have the same outer level electronic configuration ns 2 np 1 and therefore they all exhibit an oxidation state of 3+.

Physical properties. Aluminum is a silvery-white metal with high thermal and electrical conductivity. The metal surface is covered with a thin but very durable film of aluminum oxide Al 2 Oz.

Chemical properties. Aluminum is very active if there is no protective film of Al 2 Oz. This film prevents the interaction of aluminum with water. If the protective film is removed chemically (for example, with an alkali solution), the metal begins to vigorously interact with water, releasing hydrogen:

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

This property of aluminum is widely used to obtain various metals from their oxides by reduction with aluminum. The method is called aluminothermy . Aluminothermy can only be used to obtain those metals whose heat of formation of oxides is less than the heat of formation of Al 2 O3, for example:

When heated, aluminum reacts with the halogens sulfur, nitrogen and carbon, forming respectively halides:

Aluminum sulfide and carbide are completely hydrolyzed to form aluminum hydroxide and, accordingly, hydrogen sulfide and methane.

Aluminum easily dissolves in hydrochloric acid of any concentration:

Concentrated sulfuric and nitric acids have no effect on aluminum in the cold (passivate). At heating aluminum is capable of reducing these acids without releasing hydrogen:

IN diluted aluminum dissolves in sulfuric acid, releasing hydrogen:

IN diluted With nitric acid, the reaction proceeds with the release of nitric oxide (II):

Aluminum dissolves in solutions of alkalis and alkali metal carbonates to form tetrahydroxyaluminates:

Aluminium oxide. Al 2 O 3 has 9 crystal modifications. The most common a - modification. It is the most chemically inert; on its basis, single crystals of various stones are grown for use in the jewelry industry and technology.

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

Aluminum oxide, being amphoteric, can react not only with acids, but also with alkalis, as well as when fused with alkali metal carbonates, while giving metaaluminates:

and with acid salts:

Aluminum hydroxide- a white gelatinous substance, practically insoluble in water, with amphoteric properties. Aluminum hydroxide can be obtained by treating aluminum salts with alkalis or ammonium hydroxide. In the first case, an excess of alkali must be avoided, since otherwise the aluminum hydroxide will dissolve with the formation of complex tetrahydroxyaluminates[Al(OH) 4 ]` :

In fact, the last reaction produces tetrahydroxodiaquaaluminate ions`, however, the simplified form [Al(OH) 4 ]` is usually used to write reactions. With weak acidification, tetrahydroxoaluminates are destroyed:

Aluminum salts. Almost all aluminum salts can be obtained from aluminum hydroxide. Almost all salts of aluminum and strong acids are highly soluble in water and are highly hydrolyzed.

Aluminum halides are highly soluble in water and are dimers in their structure:

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

Potassium-aluminum alum is also known: KAl(SO 4) 2H 12H 2 O.

Aluminum acetate Al(CH 3 COO) 3 used in medicine as lotions.

Aluminosilicates. In nature, aluminum occurs in the form of compounds with oxygen and silicon - aluminosilicates. Their general formula: (Na, K) 2 Al 2 Si 2 O 8-nepheline.

Also natural aluminum compounds are: Al2O3- corundum, alumina; and compounds with general formulas Al 2 O 3 H nH 2 O And Al(OH) 3H nH 2 O- bauxite.

Receipt. Aluminum is produced by electrolysis of Al 2 O 3 melt.

Aluminum

Aluminum- chemical element of group III of the periodic system of Mendeleev (atomic number 13, atomic mass 26.98154). In most compounds, aluminum is trivalent, but at high temperatures it can also exhibit the +1 oxidation state. Of the compounds of this metal, the most important is Al 2 O 3 oxide.

Aluminum- silvery-white metal, lightweight (density 2.7 g/cm3), ductile, good conductor of electricity and heat, melting point 660 °C. It is easily drawn into wire and rolled into thin sheets. Aluminum is chemically active (in air it becomes covered with a protective oxide film - aluminum oxide) and reliably protects the metal from further oxidation. But if aluminum powder or aluminum foil is heated strongly, the metal burns with a blinding flame, turning into aluminum oxide. Aluminum dissolves even in dilute hydrochloric and sulfuric acids, especially when heated. But aluminum does not dissolve in highly diluted and concentrated cold nitric acid. When aqueous solutions of alkalis act on aluminum, 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 has the following form:

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

Aluminum also actively interacts with halogens. Aluminum hydroxide Al(OH) 3 is a white, translucent, gelatinous substance.

The earth's crust contains 8.8% aluminum. It is the third most abundant element in nature after oxygen and silicon and the first among metals. It is part of clays, feldspars, and mica. Several hundred Al minerals are known (aluminosilicates, bauxites, alunites, and others). The most important aluminum mineral, bauxite, contains 28-60% alumina - aluminum oxide Al 2 O 3.

Aluminum in its pure form was first obtained by the Danish physicist H. Oersted in 1825, although it is the most common metal in nature.

Aluminum production is carried out by electrolysis of alumina Al 2 O 3 in molten cryolite NaAlF 4 at a temperature of 950 °C.

Aluminum is used in aviation, construction, mainly in the form of aluminum alloys with other metals, electrical engineering (a substitute for copper in the manufacture of cables, etc.), food industry (foil), metallurgy (alloying additive), aluminothermy, etc.

Aluminum density, specific gravity and other characteristics.

Density - 2,7*10 3 kg/m 3 ;
Specific gravity - 2,7 G/cm 3 ;
Specific heat capacity at 20°C - 0.21 cal/deg;
Melting temperature - 658.7°C ;
Specific heat capacity of fusion - 76.8 cal/deg;
Boiling temperature - 2000°C ;
Relative volume change during melting (ΔV/V) - 6,6%;
Linear expansion coefficient(at about 20°C) : - 22.9 *10 6 (1/deg);
Aluminum thermal conductivity coefficient - 180 kcal/m*hour*deg;

Aluminum elastic moduli and Poisson's ratio

Reflection of light by aluminum

The numbers given in the table show what percentage of light incident perpendicular to the surface is reflected from it.

ALUMINUM OXIDE Al 2 O 3

Aluminum oxide Al 2 O 3, also called alumina, occurs in nature in crystalline form, forming the mineral corundum. Corundum has very high hardness. Its transparent crystals, colored red or blue, represent the precious stones ruby ​​and sapphire. Currently, rubies are produced artificially by alloying with alumina in an electric furnace. They are used not so much for decoration as 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.

Corundum and its fine-grained variety containing a large amount of impurities - emery, are used as abrasive materials.

ALUMINUM PRODUCTION

The main raw material for aluminum production bauxites containing 32-60% alumina Al 2 O 3 are used. The most important aluminum ores also include alunite and nepheline. Russia has significant reserves of aluminum ores. In addition to bauxite, large deposits of which are located in the Urals and Bashkiria, a rich source of aluminum is nepheline, mined on the Kola Peninsula. A lot of aluminum is also found in deposits in Siberia.

Aluminum is produced from aluminum oxide Al 2 O 3 by the electrolytic method. The aluminum oxide used for this must be sufficiently pure, since impurities are difficult to remove from smelted aluminum. Purified Al 2 O 3 is obtained by processing natural bauxite.

The main starting material for aluminum production is aluminum oxide. It does not conduct electricity and has a very high melting point (about 2050 °C), so it requires too much energy.

It is necessary to reduce the melting point of aluminum oxide to at least 1000 o C. This method was simultaneously discovered by the Frenchman P. Héroux and the American C. Hall. They discovered that alumina dissolves well in molten cryolite, a mineral with the composition AlF 3. 3NaF. This melt is subjected to electrolysis at a temperature of only about 950 °C in aluminum production. Reserves of cryolite in nature are insignificant, so synthetic cryolite was created, which significantly reduced the cost of aluminum production.

A molten mixture of cryolite Na 3 and aluminum oxide is subjected to hydrolysis. A mixture containing about 10 weight percent Al 2 O 3 melts at 960 °C and has electrical conductivity, density and viscosity that are most favorable for the process. To further improve these characteristics, AlF 3, CaF 2 and MgF 2 additives are added to the mixture. Thanks to this, electrolysis is possible at 950 °C.

The electrolyser for aluminum smelting is an iron casing lined with refractory bricks on the inside. Its bottom (under), assembled from blocks of compressed coal, serves as a cathode. Anodes (one or more) are located on top: these are aluminum frames filled with coal briquettes. In modern plants, electrolysers are installed in series; each series consists of 150 or more electrolysers.

During electrolysis, aluminum is released at the cathode and oxygen at the anode. Aluminum, which has a higher density than the original melt, is collected at the bottom of the electrolyzer, from where it is periodically released. As the metal is released, new portions of aluminum oxide are added to the melt. The oxygen released during electrolysis interacts with the carbon of the anode, which burns out, forming CO and CO 2 .

The first aluminum smelter in Russia was built in 1932 in Volkhov.

ALUMINUM ALLOYS

Alloys, which increase the strength and other properties of aluminum, are obtained by introducing alloying additives into it, such as copper, silicon, magnesium, zinc, manganese.

Duralumin(duralumin, duralumin, from the name of the German city where industrial production of the alloy began). Aluminum alloy (base) with copper (Cu: 2.2-5.2%), magnesium (Mg: 0.2-2.7%) manganese (Mn: 0.2-1%). Subject to hardening and aging, often clad with aluminum. It is a structural material for aviation and transport engineering.

Silumin- light casting alloys of aluminum (base) with silicon (Si: 4-13%), sometimes up to 23% and some other elements: Cu, Mn, Mg, Zn, Ti, Be). They produce parts of complex configurations, mainly in the automotive and aircraft industries.

Magnalia- alloys of aluminum (base) with magnesium (Mg: 1-13%) and other elements, possessing high corrosion resistance, good weldability, and high ductility. They produce shaped castings (casting magnalia), sheets, wire, rivets, etc. (deformable magnalia).

The main advantages of all aluminum alloys are their low density (2.5-2.8 g/cm3), high strength (per unit weight), satisfactory resistance to atmospheric corrosion, comparative cheapness and ease of production and processing.

Aluminum alloys are used in rocketry, aircraft, auto, shipbuilding and instrument making, in the production of tableware, sporting goods, furniture, advertising and other industries.

Aluminum alloys occupy second place in terms of the breadth of application after steel and cast iron.

Aluminum is one of the most common additives in alloys based on copper, magnesium, titanium, nickel, zinc, and iron.

Aluminum is also used for aluminizing (aluminizing)- saturating the surface of steel or cast iron products with aluminum in order to protect the base material from oxidation under strong heating, i.e. increasing heat resistance (up to 1100 °C) and resistance to atmospheric corrosion.

Aluminum was first isolated in its pure form by Friedrich Wöhler. A German chemist heated anhydrous chloride of the element with potassium metal. This happened in the 2nd half of the 19th century. Until the 20th century kg aluminum cost more.

Only the rich and state-owned could afford the new metal. The reason for the high cost is the difficulty of separating aluminum from other substances. A method for extracting the element on an industrial scale was proposed by Charles Hall.

In 1886, he dissolved the oxide in molten cryolite. The German enclosed the mixture in a granite vessel and connected an electric current to it. Plaques of pure metal settled to the bottom of the container.

Chemical and physical properties of aluminum

What aluminum? Silvery white, shiny. Therefore, Friedrich Wöhler compared the metal granules he obtained with. But there was a caveat: aluminum is much lighter.

Plasticity is close to precious and. Aluminum is a substance, easily drawn into thin wire and sheets. Just remember the foil. It is made on the basis of the 13th element.

Aluminum is lightweight due to its low density. It is three times less than that of iron. At the same time, the 13th element is almost as strong as it is.

This combination has made silver metal indispensable in industry, for example, in the production of car parts. We are also talking about handicraft production, because aluminum welding possible even at home.

Aluminum formula allows you to actively reflect light, but also heat rays. The electrical conductivity of the element is also high. The main thing is not to heat it up too much. It will melt at 660 degrees. If the temperature rises a little higher, it will burn.

The metal will disappear, only aluminium oxide. It is also formed under standard conditions, but only in the form of a surface film. It protects the metal. Therefore, it resists corrosion well, because oxygen access is blocked.

The oxide film also protects the metal from water. If you remove plaque from the surface of aluminum, a reaction with H 2 O will start. The release of hydrogen gases will occur even at room temperature. So, aluminum boat does not turn into smoke only due to the oxide film and protective paint applied to the ship’s hull.

Most active aluminum interaction with non-metals. Reactions with bromine and chlorine take place even under normal conditions. As a result, they are formed aluminum salts. Hydrogen salts are obtained by combining the 13th element with acid solutions. The reaction will also take place with alkalis, but only after the removal of the oxide film. Pure hydrogen will be released.

Application of aluminum

Metal is sprayed onto mirrors. Good light reflectance. The process takes place under vacuum conditions. They make not only standard mirrors, but also objects with mirror surfaces. These are: ceramic tiles, household appliances, lamps.

Duet aluminum-copper– the base is duralumin. Simply called duralumin. Add as quality. The composition is 7 times stronger than pure aluminum, therefore, it is suitable for mechanical engineering and aircraft construction.

Copper gives the 13th element strength, but not heaviness. Dural remains 3 times lighter than iron. Small mass of aluminum– a guarantee of lightness of cars, planes, ships. This simplifies transportation and operation, and reduces the price of products.

Buy aluminum automakers are also keen because its alloys can easily be coated with protective and decorative compounds. The paint applies faster and more evenly than on steel and plastic.

At the same time, the alloys are malleable and easy to process. This is valuable, given the mass of bends and design transitions on modern car models.

The 13th element is not only easy to dye, but can also act as a dye itself. Purchased in the textile industry aluminum sulfate. It is also useful in printing, where insoluble pigments are required.

I wonder what solution sulfate aluminum They are also used for water purification. In the presence of the “agent,” harmful impurities precipitate and are neutralized.

Neutralizes the 13th element and acids. Particularly good at this role aluminum hydroxide. It is valued in pharmacology and medicine, adding it to heartburn medications.

Hydroxide is also prescribed for ulcers and inflammatory processes of the intestinal tract. So the drug is also available in pharmacies aluminum. Acid in the stomach - a reason to learn more about such medications.

In the USSR, bronze with an 11% addition of aluminum was also minted. The denominations of the signs are 1, 2 and 5 kopecks. They started producing it in 1926 and finished it in 1957. But the production of aluminum cans for canned food has not stopped.

Stewed meat, saury and other tourist breakfasts are still packaged in containers based on the 13th element. Such jars do not react with food; at the same time, they are light and cheap.

Aluminum powder is part of many explosive mixtures, including pyrotechnics. The industry uses blasting mechanisms based on trinitrotoluene and crushed element 13. A powerful explosive is also obtained by adding ammonium nitrate to aluminum.

In the oil industry it is necessary aluminum chloride. It plays the role of a catalyst in the decomposition of organic matter into fractions. Oil has the property of releasing gaseous, light hydrocarbons of the gasoline type, interacting with the chloride of the 13th metal. The reagent must be anhydrous. After adding chloride, the mixture is heated to 280 degrees Celsius.

In construction I often mix sodium And aluminum. It turns out to be an additive to concrete. Sodium aluminate accelerates its hardening by accelerating hydration.

The rate of microcrystallization increases, which means the strength and hardness of concrete increases. In addition, sodium aluminate saves the reinforcement laid in the solution from corrosion.

Aluminum mining

Metal closes the top three most common on earth. This explains its availability and widespread use. However, nature does not give the element to humans in its pure form. Aluminum has to be separated from various compounds. The 13th element is most abundant in bauxite. These are clay-like rocks, concentrated mainly in the tropical zone.

Bauxite is crushed, then dried, crushed again and ground in the presence of a small volume of water. It turns out to be a thick mass. It is heated with steam. At the same time, most of it, of which bauxite is also not poor, evaporates. What remains is the oxide of the 13th metal.

It is placed in industrial baths. They already contain molten cryolite. The temperature is kept at around 950 degrees Celsius. An electric current of at least 400 kA is also required. That is, electrolysis is used, just like 200 years ago, when the element was isolated by Charles Hall.

Passing through a hot solution, the current breaks the bonds between the metal and oxygen. As a result, the bottom of the bath remains clean aluminum. Reactions finished. The process is completed by casting from the sediment and sending it to the consumer, or using it to form various alloys.

The main aluminum production is located in the same place as the bauxite deposits. In the forefront - Guinea. Almost 8,000,000 tons of the 13th element are hidden in its depths. Australia is in 2nd place with an indicator of 6,000,000. In Brazil, aluminum is already 2 times less. Global reserves are estimated at 29,000,000 tons.

Aluminum price

For a ton of aluminum they ask for almost $1,500. These are the data from non-ferrous metals exchanges as of January 20, 2016. The cost is set mainly by industrialists. More precisely, the price of aluminum is influenced by their demand for raw materials. It also affects the demands of suppliers and the cost of electricity, because the production of the 13th element is energy-intensive.

Different prices are set for aluminum. He goes to the smelter. The cost is announced per kilogram, and the nature of the material being delivered matters.

So, for electrical metal they give about 70 rubles. For food-grade aluminum you can get 5-10 rubles less. They pay the same for motor metal. If you rent out a mixed variety, its price is 50-55 rubles per kilogram.

The cheapest type of scrap is aluminum shavings. You can get only 15-20 rubles for it. They will give a little more for the 13th element. This refers to containers for drinks and canned food.

Aluminum radiators are also not highly valued. The price per kilogram of scrap is about 30 rubles. These are averages. In different regions and at different points, aluminum is accepted more expensive or cheaper. Often the cost of materials depends on the volumes delivered.