Chemical formula of aluminum. Chemical and physical properties of aluminum

The chemical properties of aluminum are determined by its position in the periodic table of chemical elements.

Below are the main chemical reactions of aluminum with other chemical elements. These reactions determine the basic chemical properties of aluminum.

What does aluminum react with?

Simple substances:

• halogens (fluorine, chlorine, bromine and iodine)
• phosphorus
• carbon
• oxygen (combustion)

Complex substances:

• mineral acids (hydrochloric, phosphoric)
• sulfuric acid
• Nitric acid
• alkalis
• oxidizing agents
• oxides of less active metals (aluminothermy)

What does aluminum not react with?

Aluminum does not react:

• with hydrogen
• under normal conditions - with concentrated sulfuric acid (due to passivation - the formation of a dense oxide film)
• under normal conditions - with concentrated nitric acid (also due to passivation)

Aluminum and air

Typically, the surface of aluminum is always coated with a thin layer of aluminum oxide, which protects it from exposure to air, or more precisely, oxygen. Therefore, it is believed that aluminum does not react with air. If this oxide layer is damaged or removed, the fresh aluminum surface reacts with oxygen in the air. Aluminum can burn in oxygen with a blinding white flame to form aluminum oxide Al2O3.

Reaction of aluminum with oxygen:

• 4Al + 3O 2 -> 2Al 2 O 3

Aluminum and water

Aluminum reacts with water in the following reactions:

• 2Al + 6H 2 O = 2Al(OH) 3 + 3H 2 (1)
• 2Al + 4H 2 O = 2AlO(OH) + 3H 2 (2)
• 2Al + 3H 2 O = Al 2 O 3 + 3H 2 (3)

As a result of these reactions, the following are formed, respectively:

• modification of aluminum hydroxide bayerite and hydrogen (1)
• modification of aluminum hydroxide bohemite and hydrogen (2)
• aluminum oxide and hydrogen (3)

These reactions, by the way, are of great interest in the development of compact plants for producing hydrogen for vehicles that run on hydrogen.

All these reactions are thermodynamically possible at temperatures from room temperature to the melting point of aluminum 660 ºС. All of them are also exothermic, that is, they occur with the release of heat:

• At temperatures from room temperature to 280 ºС, the most stable reaction product is Al(OH) 3.
• At temperatures from 280 to 480 ºС, the most stable reaction product is AlO(OH).
• At temperatures above 480 ºС, the most stable reaction product is Al 2 O 3.

Thus, aluminum oxide Al 2 O 3 becomes thermodynamically more stable than Al(OH) 3 at elevated temperatures. The product of the reaction of aluminum with water at room temperature will be aluminum hydroxide Al(OH) 3.

Reaction (1) shows that aluminum should react spontaneously with water at room temperature. However, in practice, a piece of aluminum immersed in water does not react with water at room temperature or even in boiling water. The fact is that aluminum has a thin coherent layer of aluminum oxide Al 2 O 3 on its surface. This oxide film adheres firmly to the surface of the aluminum and prevents it from reacting with water. Therefore, in order to start and maintain the reaction of aluminum with water at room temperature, it is necessary to constantly remove or destroy this oxide layer.

Aluminum and halogens

Aluminum reacts violently with all halogens - these are:

• fluorine F
• chlorine Cl
• bromine Br and
• iodine (iodine) I,

with education respectively:

• fluoride AlF 3
• AlCl 3 chloride
• bromide Al 2 Br 6 and
• Al 2 Br 6 iodide.

Reactions of hydrogen with fluorine, chlorine, bromine and iodine:

• 2Al + 3F 2 → 2AlF 3
• 2Al + 3Cl 2 → 2AlCl 3
• 2Al + 3Br 2 → Al 2 Br 6
• 2Al + 3l 2 → Al 2 I 6

Aluminum and acids

Aluminum actively reacts with dilute acids: sulfuric, hydrochloric and nitric, with the formation of the corresponding salts: aluminum sulfate Al 2 SO 4, aluminum chloride AlCl 3 and aluminum nitrate Al(NO 3) 3.

Reactions of aluminum with dilute acids:

• 2Al + 3H 2 SO 4 -> Al 2 (SO 4) 3 + 3H 2
• 2Al + 6HCl -> 2AlCl 3 + 3H 2
• 2Al + 6HNO 3 -> 2Al(NO 3) 3 + 3H 2

It does not interact with concentrated sulfuric and hydrochloric acids at room temperature; when heated, it reacts to form salts, oxides and water.

Aluminum and alkalis

Aluminum in an aqueous solution of alkali - sodium hydroxide - reacts to form sodium aluminate.

The reaction of aluminum with sodium hydroxide has the form:

• 2Al + 2NaOH + 10H 2 O -> 2Na + 3H 2

Sources:

1. Chemical Elements. The first 118 elements, ordered alphabetically / ed. Wikipedians - 2018

2. Reaction of Aluminum with Water to Produce Hydrogen /John Petrovic and George Thomas, U.S. Department of Energy, 2008

Aluminum oxide(alumina) A1 2 O 3, colorless. crystals; m.p. 2044°C; t. bale 3530 °C. The only stable crystalline up to 2044°C. modification of aluminum oxide-A1 2 O 3 (corundum): rhombohedral lattice, a = 0.512 nm, = 55.25° (for hexagonal installation a = 0.475 nm, c = 1.299 nm, space group D 6 3d, z = 2); dense 3.99 g/cm 3 ;Н° pl 111.4 kJ/mol; level of temperature dependence: heat capacity C° p = = 114.4 + 12.9*10 -3 T - 34.3*10 5 T 2 JDmol*K) (298T 1800 K), vapor pressure Igp (Pa) = -54800/7+1.68 (up to ~ 3500 K); temperature coefficient linear expansion (7.2-8.6)*10 -6 K -1 (300T1200 K); thermal conductivity sample sintered at 730°C 0.35 W/(mol*K); Mohs hardness 9; the refractive index for an ordinary ray is n 0 1.765, for an extraordinary ray n 0 1.759.

Aluminum oxide (Al2O3) has an exceptional set of properties, such as:

• High hardness
• Good thermal conductivity
• Excellent corrosion resistance
• Low density
• Maintains strength over a wide temperature range
• Electrical insulating properties
• Low cost relative to other ceramic materials

All these combinations make the material irreplaceable in the manufacture of corrosion-resistant, wear-resistant, electrical insulating and heat-resistant products for a wide variety of industries.

Main Applications:

• Lining of mills, hydrocyclones, concrete mixers, extruders, conveyors, pipes and other wearable equipment
• Mechanical seal rings
• Dies, wires, guides
• Sliding bearings, shafts and lining of wet parts of chemical pumps
• Grinding media
• Papermaking equipment parts
• Burners
• Extruder nozzles (cores)
• Crucibles
• Elements of valves and shut-off valves
• Nozzles for argon-arc welding machines
• Electrical insulators

There are several modifications of aluminum oxide depending on the content of the main phase and impurities, which are distinguished by strength and chemical resistance

Aluminum hydroxide

Aluminum hydroxide Al(OH) 3 is a colorless solid, insoluble in water, found in many bauxites. It exists in four polymorphic modifications. In the cold, α-Al(OH) 3 is formed - bayerite, and when deposited from a hot solution γ-Al(OH) 3 - gibbsite (hydrargilite), both crystallize in the monoclinic system, have a layered structure, the layers consist of octahedra, between the layers there is an hydrogen bond. There is also a triclinic gibbsite γ’-Al(OH) 3 , a triclinic Nordstrandite β-Al(OH) 3 and two modifications of the oxohydroxide AlOOH - orthorhombic boehmite and diaspores. Amorphous aluminum hydroxide has a variable composition Al 2 O 3 · nH 2 O. It decomposes when heated above 180°C.

Chemical properties

Aluminum hydroxide is a typical amphoteric compound; freshly obtained hydroxide dissolves in acids and alkalis:

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

Al(OH) 3 + NaOH + 2H 2 O = Na.

When heated, it decomposes; the dehydration process is quite complex and can be schematically represented as follows:

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

2AlOOH = Al 2 O 3 + H 2 O.

Aluminum hydroxide is a chemical substance that is a compound of aluminum oxide with water. It can exist in liquid and solid states. Liquid hydroxide is a jelly-like transparent substance that is very poorly soluble in water. Solid hydroxide is a white crystalline substance that has passive chemical properties and does not react with virtually any other element or compound.

Aluminum chloride

At normal pressure it sublimes at 183 °C (under pressure it melts at 192.6 °C). Very soluble in water (44.38 g in 100 g H 2 O at 25 ° C); Due to hydrolysis, it smokes in moist air, releasing HCl. AlCl 3 · 6H 2 O crystal hydrate precipitates from aqueous solutions - yellowish-white spreading crystals. Well soluble in many organic compounds (in ethanol - 100 g per 100 g of alcohol at 25 ° C, in acetone, dichloroethane, ethylene glycol, nitrobenzene, carbon tetrachloride and etc.); however, it is practically insoluble in benzene and toluene.

Aluminum sulfate

Aluminum sulfate is a white salt with a gray, blue or pink tint; under normal conditions it exists in the form of crystalline hydrate Al 2 (SO 4) 3 ·18H 2 O - colorless crystals. When heated, it loses water without melting; when heated, it decomposes into Al 2 O 3 and SO 3 and O 2. It dissolves well in water. Technical aluminum sulfate can be obtained by treating bauxite or clay with sulfuric acid, and the pure product can be obtained by dissolving Al(OH) 3 in hot concentrated H 2 SO 4.

Aluminum sulfate is used as a coagulant for water purification for domestic, drinking and industrial purposes and for use in paper, textile, leather and other industries.

Used as a food additive E-520

Aluminum carbide

Aluminum carbide is produced by the direct reaction of aluminum with carbon in an arc furnace.

Iron with aluminum

Alni- a group of hard magnetic (highly coercive) alloys iron (Fe) - nickel (Ni) - aluminum (Al).

Alloying of alni-alloys improves their magnetic characteristics; alloying with copper is used (for example, an alloy of 24% nickel, 4% copper, 13% aluminum and 59% iron), cobalt (alnico and magnico alloys). Carbon admixture reduces the magnetic properties of the alloy; its content should not exceed 0.03%.

Alni alloys are characterized by high hardness and brittleness, so casting is used to make permanent magnets from them.

Sodium aluminate

Sodium aluminate- an inorganic compound, a complex oxide of sodium and aluminum with the formula NaAlO 2, a white amorphous substance, reacts with water.

Orthoaluminic acid

Alumina" you, salts of aluminum acids: orthoaluminum H3 AlO3, metaaluminum HAlO2, etc. In nature, the most common are Aluminates of the general formula R, where R is Mg, Ca, Be, Zn, etc. Among them are: 1) octahedral varieties, the so-called. spinels - Mg (noble spinel), Zn (ganite or zinc spinel), etc. and 2) rhombic varieties - Be (chrysoberyl), etc. (in formulas minerals the atoms that make up a structural group are usually enclosed in square brackets).

Alkali metal aluminates are obtained by reacting Al or Al(OH)3 with caustic alkalis: Al(OH)3 + KOH = KAlO2 + 2H2 O. Of these, sodium aluminates NaAlO2, formed during the alkaline process of producing alumina , used in textile production as a mordant. Aluminates of alkaline earth metals are obtained by fusing their oxides with Al2 O3; Of these, calcium aluminates CaAl2 O4 serves as the main component of rapidly hardening aluminous cement.

Aluminates of rare earth elements have acquired practical importance. They are obtained by jointly dissolving the oxides of rare earth elements R2 03 and Al(NO3 )3 in nitric acid, evaporating the resulting solution until the salts crystallize and calcining the latter at 1000-1100°C. The formation of aluminates is controlled by X-ray diffraction as well as chemical phase analysis. The latter is based on the different solubility of the initial oxides and the compound formed (A., for example, are stable in acetic acid, while oxides of rare earth elements are well soluble in it). Rare earth aluminates have great chemical resistance, depending on their pre-firing temperatures; stable in water at high temperatures (up to 350°C) under pressure. The best solvent for rare earth aluminates is hydrochloric acid. Aluminates of rare earth elements are characterized by high refractoriness and characteristic color. Their densities range from 6500 to 7500 kg /m3.

Aluminum is an amphoteric metal. The electronic configuration of the aluminum atom is 1s 2 2s 2 2p 6 3s 2 3p 1. Thus, it has three valence electrons on its outer electron layer: 2 on the 3s and 1 on the 3p sublevel. Due to this structure, it is characterized by reactions as a result of which the aluminum atom loses three electrons from the outer level and acquires an oxidation state of +3. Aluminum is a highly reactive metal and exhibits very strong reducing properties.

Interaction of aluminum with simple substances

with oxygen

When absolutely pure aluminum comes into contact with air, aluminum atoms located in the surface layer instantly interact with oxygen in the air and form a thin, tens of atomic layers thick, durable oxide film of the composition Al 2 O 3, which protects aluminum from further oxidation. It is also impossible to oxidize large samples of aluminum even at very high temperatures. However, fine aluminum powder burns quite easily in a burner flame:

4Al + 3O 2 = 2Al 2 O 3

with halogens

Aluminum reacts very vigorously with all halogens. Thus, the reaction between mixed aluminum and iodine powders occurs already at room temperature after adding a drop of water as a catalyst. Equation for the interaction of iodine with aluminum:

2Al + 3I 2 =2AlI 3

Aluminum also reacts with bromine, which is a dark brown liquid, without heating. Simply add a sample of aluminum to liquid bromine: a violent reaction immediately begins, releasing a large amount of heat and light:

2Al + 3Br 2 = 2AlBr 3

The reaction between aluminum and chlorine occurs when heated aluminum foil or fine aluminum powder is added to a flask filled with chlorine. Aluminum burns effectively in chlorine according to the equation:

2Al + 3Cl 2 = 2AlCl 3

with sulfur

When heated to 150-200 o C or after igniting a mixture of powdered aluminum and sulfur, an intense exothermic reaction begins between them with the release of light:

— sulfide aluminum

with nitrogen

When aluminum reacts with nitrogen at a temperature of about 800 o C, aluminum nitride is formed:

with carbon

At a temperature of about 2000 o C, aluminum reacts with carbon and forms aluminum carbide (methanide), containing carbon in the -4 oxidation state, as in methane.

Interaction of aluminum with complex substances

with water

As mentioned above, a stable and durable oxide film of Al 2 O 3 prevents aluminum from oxidizing in air. The same protective oxide film makes aluminum inert towards water. When removing the protective oxide film from the surface by methods such as treatment with aqueous solutions of alkali, ammonium chloride or mercury salts (amalgiation), aluminum begins to react vigorously with water to form aluminum hydroxide and hydrogen gas:

with metal oxides

After igniting a mixture of aluminum with oxides of less active metals (to the right of aluminum in the activity series), an extremely violent, highly exothermic reaction begins. Thus, in the case of interaction of aluminum with iron (III) oxide, a temperature of 2500-3000 o C develops. As a result of this reaction, high-purity molten iron is formed:

2AI + Fe 2 O 3 = 2Fe + Al 2 O 3

This method of obtaining metals from their oxides by reduction with aluminum is called aluminothermy or aluminothermy.

with non-oxidizing acids

The interaction of aluminum with non-oxidizing acids, i.e. with almost all acids, except concentrated sulfuric and nitric acids, leads to the formation of an aluminum salt of the corresponding acid and hydrogen gas:

a) 2Al + 3H 2 SO 4 (diluted) = Al 2 (SO 4) 3 + 3H 2

2Al 0 + 6H + = 2Al 3+ + 3H 2 0 ;

b) 2AI + 6HCl = 2AICl3 + 3H2

with oxidizing acids

-concentrated sulfuric acid

The interaction of aluminum with concentrated sulfuric acid under normal conditions and at low temperatures does not occur due to an effect called passivation. When heated, the reaction is possible and leads to the formation of aluminum sulfate, water and hydrogen sulfide, which is formed as a result of the reduction of sulfur, which is part of sulfuric acid:

Such a deep reduction of sulfur from the oxidation state +6 (in H 2 SO 4) to the oxidation state -2 (in H 2 S) occurs due to the very high reducing ability of aluminum.

- concentrated nitric acid

Under normal conditions, concentrated nitric acid also passivates aluminum, which makes it possible to store it in aluminum containers. Just as in the case of concentrated sulfuric acid, the interaction of aluminum with concentrated nitric acid becomes possible with strong heating, and the reaction predominantly occurs:

- dilute nitric acid

The interaction of aluminum with diluted nitric acid compared to concentrated nitric acid leads to products of deeper nitrogen reduction. Instead of NO, depending on the degree of dilution, N 2 O and NH 4 NO 3 can be formed:

8Al + 30HNO 3(dil.) = 8Al(NO 3) 3 +3N 2 O + 15H 2 O

8Al + 30HNO 3(pure dilute) = 8Al(NO 3) 3 + 3NH 4 NO 3 + 9H 2 O

with alkalis

Aluminum reacts both with aqueous solutions of alkalis:

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

and with pure alkalis during fusion:

In both cases, the reaction begins with the dissolution of the protective film of aluminum oxide:

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

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

In the case of an aqueous solution, aluminum, cleared of the protective oxide film, begins to react with water according to the equation:

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

The resulting aluminum hydroxide, being amphoteric, reacts with an aqueous solution of sodium hydroxide to form soluble sodium tetrahydroxoaluminate:

Al(OH) 3 + NaOH = Na

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

History of the discovery of aluminum

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

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

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

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

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

General characteristics of the aluminum atom

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

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

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

Aluminum as a simple substance: physical properties

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

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

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

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

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

Chemical properties of aluminum

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

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

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

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

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

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

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

Regenerative capacity

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

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

Distribution in nature

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

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

The most common substances containing the metal in question:

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

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

Receipt

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

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

Application

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

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

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

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

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

Properties of aluminum hydroxide

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

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

Aluminum and its compounds

The main subgroup of group III of the periodic table consists of boron (B), aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).

As can be seen from the above data, all these elements were discovered in the 19th century.

Boron is a non-metal. Aluminum is a transition metal, while gallium, indium and thallium are full-fledged metals. Thus, with increasing radii of the atoms of the elements of each group of the periodic table, the metallic properties of simple substances increase.

The position of aluminum in D. I. Mendeleev’s table. Atomic structure, oxidation states

The element aluminum is located in group III, the main “A” subgroup, period 3 of the periodic system, serial number No. 13, relative atomic mass Ar(Al) = 27. Its neighbor on the left in the table is magnesium - a typical metal, and on the right - silicon - already non-metal. Consequently, aluminum must exhibit properties of some intermediate nature and its compounds are amphoteric.

Al +13) 2) 8) 3, p – element,

Aluminum exhibits an oxidation state of +3 in compounds:

Al 0 – 3 e - → Al +3

Physical properties

Aluminum in its free form is a silvery-white metal with high thermal and electrical conductivity. The melting point is 650 o C. Aluminum has a low density (2.7 g/cm 3) - about three times less than that of iron or copper, and at the same time it is a durable metal.

Being in nature

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

In nature, aluminum occurs only in compounds(minerals).

Some of them:

· Bauxite - Al 2 O 3 H 2 O (with impurities of SiO 2, Fe 2 O 3, CaCO 3)

· Nephelines - KNa 3 4

Alunites - KAl(SO 4) 2 2Al(OH) 3

· Alumina (mixtures of kaolins with sand SiO 2, limestone CaCO 3, magnesite MgCO 3)

Corundum - Al 2 O 3 (ruby, sapphire)

· Feldspar (orthoclase) - K 2 O×Al 2 O 3 ×6SiO 2

Kaolinite - Al 2 O 3 × 2SiO 2 × 2H 2 O

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

· Beryl - 3BeO Al 2 O 3 6SiO 2

Chemical properties of aluminum and its compounds

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

Its thickness is 0.00001 mm, but thanks to it, aluminum does not corrode. To study the chemical properties of aluminum, the oxide film is removed. (Using sandpaper, or chemically: first dipping it into an alkali solution to remove the oxide film, and then into a solution of mercury salts to form an alloy of aluminum with mercury - amalgam).