Characteristics of aluminum according to chemistry plan. Aluminum: chemical and physical properties

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

The simple substance aluminum is a light, paramagnetic silver-white metal that can be easily formed, cast, and machined. Aluminum has high thermal and electrical conductivity and resistance to corrosion due to the rapid formation of strong oxide films that protect the surface from further interaction.

Modern production method, Hall-Heroult process. It consists of dissolving aluminum oxide Al2O3 in molten cryolite Na3AlF6, followed by electrolysis using consumable coke or graphite anode electrodes. This production method requires very large amounts of electricity, and therefore received industrial application only in the 20th century.

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

The metal is silver-white, light, density - 2.7 g/cm³, melting point for technical aluminum - 658 °C, for high-purity aluminum - 660 °C, high ductility: for technical aluminum - 35%, for pure aluminum - 50% , rolled into thin sheets and even foil. Aluminum has high electrical conductivity (37·106 S/m) and thermal conductivity (203.5 W/(m·K)), 65%, and has high light reflectivity.

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

In terms of prevalence in the Earth's crust, it ranks 1st among metals and 3rd among elements, second only to 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 its high chemical activity, is found almost exclusively in the form of compounds.

Natural aluminum consists almost entirely of a single stable isotope, 27Al, with negligible traces of 26Al, the longest-lived radioactive isotope with a half-life of 720 thousand years, formed in the atmosphere when 40Ar argon nuclei are split by high-energy cosmic ray protons.

Under normal conditions, aluminum is covered with a thin and durable oxide film and therefore does not react with classical oxidizing agents: H2O (t°), O2, HNO3 (without heating). Thanks to this, aluminum is practically not subject to corrosion and is therefore widely in demand in modern industry. However, when the oxide film is destroyed (for example, upon contact with solutions of ammonium salts NH4+, hot alkalis or as a result of amalgamation), aluminum acts as an active reducing metal. You can prevent the formation of an oxide film by adding metals such as gallium, indium or tin to aluminum. In this case, the aluminum surface is wetted by low-melting eutectics based on these metals.

Reacts easily with simple substances:

with oxygen, forming aluminum oxide:

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

reacts with other non-metals when heated:

with fluorine to form aluminum fluoride:

with sulfur, forming aluminum sulfide:

with nitrogen to form aluminum nitride:

with carbon, forming aluminum carbide:

Aluminum sulfide and carbide are completely hydrolyzed:

With complex substances:

with water (after removing the protective oxide film, for example, amalgamation or hot alkali solutions):

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

Easily dissolves in hydrochloric and dilute sulfuric acids:

When heated, it dissolves in acids - oxidizing agents that form soluble aluminum salts:

reduces metals from their oxides (aluminothermy):

44. Aluminum compounds, their amphoteric properties

Electronic configuration of the external level of aluminum ... 3s23p1.

In the excited state, one of the s-electrons goes to a free cell of the p-sublevel; this state corresponds to valence III and oxidation state +3. In the outer electron layer of the aluminum atom there are free d-sublevels.

The most important natural compounds are aluminosilicates:

white clay Al2O3 ∙ 2SiO2 ∙ 2H2O, feldspar K2O ∙ Al2O3 ∙ 6SiO2, mica K2O ∙ Al2O3 ∙ 6SiO2 ∙ H2O

Of the other natural forms of aluminum, the most important are bauxite А12Оз ∙ nН2О, minerals corundum А12Оз and cryolite А1Fз ∙ 3NaF.

A lightweight, silver-white, ductile metal that conducts electricity and heat well.

In air, aluminum is coated with a thin (0.00001 mm) but very dense oxide film, which protects the metal from further oxidation and gives it a matte appearance.

Aluminum oxide A12O3

White solid, insoluble in water, melting point 20500C.

Natural A12O3 is the mineral corundum. Transparent colored corundum crystals - red ruby ​​- contains 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.

Chemical properties

Aluminum oxide exhibits amphoteric properties

1. interaction with acids

А12О3 +6HCl = 2AlCl3 + 3H2O

2. interaction with alkalis

А12О3 + 2NaOH – 2NaAlO2 + H2O

Al2O3 + 2NaOH + 5H2O = 2Na

3. 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

2A1 + WO3 = A12Oz + W

4. interaction with salts that have a highly alkaline environment due to hydrolysis

Al2O3 + Na2CO3 = 2 NaAlO2 + CO2

Aluminum hydroxide A1(OH)3

Al(OH)3 is a voluminous gelatinous white precipitate, practically insoluble in water, but easily soluble in acids and strong alkalis. It therefore has an amphoteric character.

Aluminum hydroxide is obtained by the exchange of soluble aluminum salts with alkalis

AlCl3 + 3NaOH = Al(OH)3↓ + 3NaCl

Al3+ + 3OH- = Al(OH)3↓

This reaction can be used as a qualitative reaction for the Al3+ ion

Chemical properties

1. interaction with acids

Al(OH)3 +3HCl = 2AlCl3 + 3H2O

2. upon interaction with strong alkalis, the corresponding aluminates are formed:

NaOH + A1(OH)3 = Na

3. thermal decomposition

2Al(OH)3 = Al2O3 + 3H2O

Aluminum salts undergo hydrolysis into the cation; the medium is acidic (pH< 7)

Al3+ + H+OH- ↔ AlOH2+ + H+

Al(NO3)3 + H2O↔ AlOH(NO3)2 + HNO3

Soluble aluminum salts and weak acids undergo complete (irreversible hydrolysis)

Al2S3+ 3H2O = 2Al(OH)3 +3H2S

Aluminum oxide Al2O3 - included in some antacids (for example, Almagel), used for increased acidity of gastric juice.

КAl(SO4)3 12H2О – potassium aluminum alum is used in medicine for the treatment of skin diseases, as a hemostatic agent. It is also used as a tannin in the leather industry.

(CH3COO)3Al - Burov's liquid - 8% solution of aluminum acetate has an astringent and anti-inflammatory effect, and in high concentrations it has moderate antiseptic properties. It is used in diluted form for rinsing, lotions, and for inflammatory diseases of the skin and mucous membranes.

AlCl3 - used as a catalyst in organic synthesis.

Al2(SO4)3 18 H20 – used for water purification.

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 modulus 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 ore. 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, 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.

>> Chemistry: Aluminum

Structure and properties of atoms. Aluminum Al is an element of the main subgroup of group III of D. I. Mendeleev’s Periodic Table. Atom aluminum contains three electrons in its outer energy level, which it easily gives up during chemical interactions. The ancestor of the subgroup and the upper neighbor of aluminum, boron, has a smaller atomic radius (for boron it is 0.080 nm, for aluminum it is 0.143 nm). In addition, the aluminum atom has one intermediate eight-electron layer (2e-; 8e-; Ze-), which prevents the attraction of outer electrons to the nucleus. Therefore, aluminum atoms have much stronger reducing properties than boron atoms, which exhibit non-metallic properties.

In almost all of its compounds, aluminum has an oxidation state of +3.

Aluminum- a simple substance. Silver-white light metal. Melts at 660 °C. It is very plastic, easily drawn into wire and rolled into foil 0.01 mm thick. It has very high electrical and thermal conductivity. Forms light and strong alloys with other metals.

What chemical reaction was based on the story “Sparklers” by its author N. Nosov?

What physical and chemical properties are the use of aluminum and its alloys in technology based on?

Write in ionic form the equations for the reactions between solutions of aluminum sulfate and potassium hydroxide with a deficiency and excess of the latter.

Write the reaction equations for the following transformations: Al -> AlCl3 -> Al(0H)3 -> Al2O3 -> NaAl02 -> Al2(SO4)3 -> Al(OH)3 -> AlCl3 -> NaAlO2

Write reactions involving electrolytes in ionic form. Consider the first reaction as a redox process.

Chemical element of group III of the periodic system of Mendeleev.

Latin name- Aluminum.

Designation- Al.

Atomic number — 13.

Atomic mass — 26,98154.

Density- 2.6989 g/cm3.

Melting temperature— 660 °С.

A simple, lightweight, paramagnetic metal of light gray or silvery white color. It has high thermal conductivity and electrical conductivity, and is resistant to corrosion. Distribution in the earth's crust - 8.8% by mass - it is the most common metal and the third most common chemical element.

It is used as a structural material in the construction of buildings, aircraft and shipbuilding, for the manufacture of conductive products in electrical engineering, chemical equipment, consumer goods, the production of other metals using aluminothermy, as a component of solid rocket fuel, pyrotechnic compositions, and the like.

Aluminum metal was first produced by the Danish physicist Hans Christian Oersted.

In nature, it is found exclusively in the form of compounds, as it has high chemical activity. Forms a strong chemical bond with oxygen. Due to its reactivity, it is very difficult to obtain metal from ore. Currently, the Hall-Heroult method is used, which requires large amounts of electricity.

Aluminum forms alloys with almost all metals. The most famous are duraluminium (an alloy with copper and magnesium) and silumin (an alloy with silicon). Under normal conditions, aluminum is covered with a durable oxide film, so it does not react with classical oxidizing agents water (H 2 O), oxygen (O 2) and nitric acid (HNO 3). Thanks to this, it is practically not subject to corrosion, which ensured its demand in industry.

The name comes from the Latin “alumen”, which means “alum”.

Application of aluminum in medicine

Traditional medicine

The role of aluminum in the body is not fully understood. It is known that its presence stimulates the growth of bone tissue, the development of epithelium and connective tissues. Under its influence, the activity of digestive enzymes increases. Aluminum is related to the restoration and regeneration processes of the body.

Aluminum is considered a toxic element for human immunity, but nevertheless, it is part of cells. In this case, it has the form of positively charged ions (Al3+), which affect the parathyroid glands. Different types of cells contain different amounts of aluminum, but it is known that liver, brain and bone cells accumulate it faster than others.

Medicines containing aluminum have analgesic and enveloping effects, antacid and adsorbent effects. The latter means that when interacting with hydrochloric acid, medications can reduce the acidity of gastric juice. Aluminum is also prescribed for external use: in the treatment of wounds, trophic ulcers, acute conjunctivitis.

The toxicity of aluminum is manifested in its replacement of magnesium in the active centers of a number of enzymes. Its competitive relationship with phosphorus, calcium and iron also plays a role.

With a lack of aluminum, weakness in the limbs is observed. But such a phenomenon is almost impossible in the modern world, since the metal comes with water, food and through polluted air.

With excessive aluminum content in the body, changes in the lungs, convulsions, anemia, spatial disorientation, apathy, and memory loss begin.

Ayurveda

Aluminum is considered poisonous and should not be used for treatment. Likewise, you should not use aluminum containers for preparing decoctions or storing herbs.

Use of aluminum in magic

Due to the difficulty of obtaining a pure element, the metal was used in magic along with, and jewelry was made from it. When the production process became simpler, the fashion for aluminum crafts immediately passed.

Protective magic

Only aluminum foil is used, which has the properties of shielding energy flows, preventing them from spreading. Therefore, as a rule, objects that can spread negative energy around themselves are wrapped in it. Very often dubious magical gifts are wrapped in foil - wands, masks, daggers, especially those brought from Africa or Egypt.

They do the same with planted unknown objects found in the yard or under the door. Instead of lifting it with your hands or through a cloth, it is better to cover it with foil without touching the object itself.

Sometimes foil is used as a protective screen for amulets and talismans that are not currently needed, but may be required in the future.

Aluminum in astrology

Zodiac sign: Capricorn.

DEFINITION

Aluminum- the thirteenth element of the periodic table. Designation - Al from the Latin "aluminum". Located in the third period, IIIA group. Refers to metals. The nuclear charge is 13.

Aluminum is the most common metal in the earth's crust. It is a component of clays, feldspars, micas and many other minerals. The total aluminum content in the earth's crust is 8% (mass.).

Aluminum is a silvery-white (Fig. 1) lightweight metal. It is easily drawn into wire and rolled into thin sheets.

At room temperature, aluminum does not change in air, but only because its surface is covered with a thin film of oxide, which has a very strong protective effect.

Rice. 1. Aluminum. Appearance.

Atomic and molecular mass of aluminum

Relative molecular mass of the substance (Mr) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.

Since in the free state aluminum exists in the form of monatomic Al molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 26.9815.

Isotopes of aluminum

It is known that in nature aluminum can be found in the form of one stable isotope 27 Al. The mass number is 27. The nucleus of an atom of the aluminum isotope 27 Al contains thirteen protons and fourteen neutrons.

There are radioactive isotopes of aluminum with mass numbers from 21 to 42, among which the longest-lived isotope 26 Al, whose half-life is 720 thousand years.

Aluminum ions

At the outer energy level of the aluminum atom there are three electrons, which are valence:

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

As a result of chemical interaction, aluminum gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Al 0 -3e → Al 3+ .

Aluminum molecule and atom

In the free state, aluminum exists in the form of monoatomic Al molecules. Here are some properties characterizing the aluminum atom and molecule:

Aluminum alloys

The main use of aluminum is the production of alloys based on it. Alloying additives (for example, copper, silicon, magnesium, zinc, manganese) are added to aluminum mainly to increase its strength.

Duralumins containing copper and magnesium, silumins in which the main additive is silicon, magnalium (an alloy of aluminum with 9.5-11.5% magnesium) are widely used.

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

Examples of problem solving

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