The structure of the outer electron layers in the atoms of the elements of group I allows us, first of all, to assume that they have no tendency to add electrons. On the other hand, the return of the only outer electron, it would seem, should occur very easily and lead to the formation of stable monovalent cations of the elements under consideration.

As experience shows, these assumptions are fully justified only in relation to the elements of the left column (Li, Na, K and analogues). For copper and its analogues, they are only half true: in the sense that they do not have a tendency to attach electrons. At the same time, their 18-electron layer, which is the most remote from the nucleus, is not yet completely fixed and, under certain conditions, is capable of partial loss of electrons. The latter determines the possibility of existence, along with monovalent Cu, Agand Auas well as compounds of the elements under consideration, corresponding to their higher valency.

Such a discrepancy between the assumptions derived from atomic models and the results of experiment shows that consideration of the properties of elements based ononlyelectronic structures of atoms and without taking into account other features is not always enough for chemical characterization these elements even in the most rough outlines.

alkali metals.

The name alkali metals applied to the elements of the Li-Cs series is due to the fact that their hydroxides are strong alkalis. Sodium and potassium are among the most common elements, accounting for 2.0 and 1.1%, respectively, of the total number of atoms in the earth's crust. Content in it lithium (0,02%), rubidium (0.004%) and cesium (0.00009%) is already much less, and France - negligible. Elemental Na and K were isolated only in 1807. Lithium was discovered in 1817, cesium and rubidium - in 1860 and 1861, respectively. Element No. 87 - francium - was discovered in 1939, and received its name in 1946. Natural sodium and cesium are "pure" elements (23 Na and 133 Cs), lithium is made up of isotopes 6 Li (7.4%) and 7 Li (92.6%), potassium is made up of isotopes 39 K (93.22%) .
40 K (0.01%) and 41 K (6.77%), rubidium - from the isotopes 85 Rb (72.2%) and 87 Rb (27.8%). Of the isotopes of francium, the most important is the naturally occurring 223 Fr ( average duration atom life 32 min).

Prevalence:

In nature, only compounds of alkali metals are found. Sodium and potassium are permanent constituents of many silicates. Of the individual sodium minerals, the most important is salt (NaCl) is part of sea water and in some areas earth's surface forms huge deposits under a layer of alluvial rocks rock salt. The upper layers of such deposits sometimes contain accumulations of potassium salts in the form of layers. sylvinite (mKCl∙nNaCl), ka rnallite (KCl MgCl 2 6H 2 O), etc., which serve as the main source for obtaining compounds of this element. Only a few natural accumulations of potassium salts of industrial importance are known. A number of minerals are known for lithium, but their accumulations are rare. Rubidium and cesium occur almost exclusively as impurities in potassium. Traces of francium are always found in uranium ores . Lithium minerals are, for example, spodumene and lepidolite (Li 2 KAl ). Part of the potassium in the last of them is sometimes replaced by rubidium. The same applies to carnallite, which can serve good source getting rubidium. For cesium technology, the relatively rare mineral is most important pollucite - CsAI(SiO 3) 2 .

Receipt:

In the free state, alkali metals can be isolated by electrolysis of their molten chloride salts. Of major practical importance is sodium, the annual world production of which is more than 200 thousand tons. The installation diagram for its production by electrolysis of molten NaCl is shown below. The bath consists of a steel casing with a fireclay lining, a graphite anode (A) and an annular iron cathode (K), between which there is a mesh diaphragm. The electrolyte is usually not pure NaCl (mp 800 ℃), but a more fusible mixture of about 40% NaCl and 60% CaCl 2, which makes it possible to work at temperatures of about 580 °C. The metallic sodium collected in the upper part of the annular cathode space and passing into the collector contains a small (up to 5%) admixture of calcium, which is then almost completely released (the solubility of Ca in liquid sodium at its melting point is only 0.01%). As the electrolysis proceeds, NaCl is added to the bath. Electricity consumption is about 15 kWh per 1 kg of Na.

2NaCl→ 2Na+Cl 2

It is interesting:

Before the introduction of the electrolytic method, metallic sodium was obtained by heating soda with coal according to the reaction:

Na 2 CO 3 + 2C + 244kcal → 2Na + 3CO

The production of metallic K and Li is incomparably less than that of sodium. Lithium is obtained by electrolysis of a LiCl + KCl melt, and potassium is obtained by the action of sodium vapor on a KCl melt, which flows countercurrently to them in special distillation columns (from the upper part of which potassium vapor exits). Rubidium and cesium are hardly mined on a large scale. To obtain small amounts of these metals, it is convenient to use vacuum heating of their chlorides with calcium metal.

2LiCl→2Li+Cl 2

Physical properties:

In the absence of air, lithium and its analogues are silvery-white (with the exception of yellowish cesium) substances with a more or less strong metallic luster. All alkali metals are characterized by low densities, low hardness, low melting and boiling points, and good electrical conductivity. Their most important constants are compared below:

Density, g/cm3.

Melting point, °С

Boiling point, °С

Due to the low density of Li, Na and K float on water (Li - even on kerosene). Alkali metals are easily cut with a knife, and the hardness of the softest of them - cesium - does not exceed the hardness of wax. The non-luminous flame of a gas burner is dyed by alkali metals and their volatile compounds in characteristic colors, of which the bright yellow inherent in sodium is the most intense.

It is interesting:

Externally manifested in the form of flame coloring, the emission of light rays by heated alkali metal atoms is due to the jump of electrons from higher to lower energy levels. For example, the characteristic yellow line of the sodium spectrum appears when an electron jumps from the 3p level to the 3s level. Obviously, for the possibility of such a jump, a preliminary excitation of the atom is necessary, i.e., the transfer of one or several of its electrons to a higher energy level. In the case under consideration, excitation is achieved due to the heat of the flame (and requires an expenditure of 48 kcal/g-atom), but in general it can follow as a result of the communication of energy to the atom various kinds. Other alkali metals cause the following flame colors: Li - carmine red, K-violet, Rb - bluish red, Cs - blue.

The luminescence spectrum of the night sky shows the constant presence of yellow sodium radiation in it. The height of the place of its occurrence is estimated at 200-300 km.T. That is, the atmosphere at these altitudes contains sodium atoms (of course, in negligible amounts). The appearance of radiation is described by a number of elementary processes (an asterisk indicates an excited state; M is any third particle - O 2, O 0, N 2, etc.): Na + O 0 + M \u003d NaO + M *, then NaO + O \u003d O 2 + Na* and finally Na*= Na +λν.

Sodium and potassium should be stored in tightly closed vessels under a layer of dry and neutral kerosene. Their contact with acids, water, chlorinated organic compounds and solid carbon dioxide is unacceptable. It is impossible to accumulate small cuttings of potassium, which oxidize especially easily (due to their relatively large surface). Unused residues of potassium and sodium in small quantities are destroyed by interaction with an excess of alcohol, in large quantities - by burning on the coals of a fire. Alkali metals that have caught fire in the room are best extinguished by falling asleep with dry powder of soda ash.

Chemical properties:

From the chemical point of view, lithium and its analogues are exclusively reactive metals (moreover, their activity usually increases in the direction from Li to Cs). In all compounds, alkali metals are monovalent. Located in the extreme left part of the series of voltages, they interact vigorously with water according to the scheme:

2E + 2H 2 O \u003d 2EON + H 2

In the reaction with Li and Na, the evolution of hydrogen is not accompanied by its ignition; in K, it already occurs, while in Rb and Cs, the interaction proceeds with an explosion.

· In contact with air, fresh sections of Na and K (to a lesser extent, Li) are immediately covered with a loose film of oxidation products. In view of this, Na and K are usually stored under kerosene. Na and K heated in air ignite easily, while rubidium and cesium ignite spontaneously even at ordinary temperatures.

4E + O 2 → 2E 2 O (for lithium)

2E + O 2 → E 2 O 2 (for sodium)

E+O 2 →EO 2(for potassium, rubidium and cesium)

Practical application is found mainly by sodium peroxide (Na 2 0 2). Technically, it is obtained by oxidation at 350 ° C of sprayed metallic sodium:

2Na+O 2 →Na 2 O 2 +122 kcal

Melts of simple substances are able to combine with ammonia, with the formation of amides and imides, solvates:

2Na melt +2NH 3 →2NaNH 2 +H 2 (sodium amide)

2Na melt +NH 3 →Na 2 NH+H 2 (sodium imide)

Na melt +6NH 3 → (sodium solvate)

When peroxides interact with water, the following reaction occurs:

2E 2 O 2 + 2H 2 O \u003d 4EOH + O 2

The interaction of Na 2 O 2 with water is accompanied by hydrolysis:

Na 2 O 2 + 2H 2 O → 2NaOH + H 2 O 2 +34 kcal

It is interesting:

InteractionNa 2 O 2 with carbon dioxide according to the scheme

2Na 2 O 2 + 2CO 2 \u003d 2Na 2 CO 3 + O 2 +111 kcal

serves as the basis for the use of sodium peroxide as a source of oxygen in insulating gas masks and on submarines. Pure or containing various additives (for example, bleach mixed with Ni or C saltsu) sodium peroxide wears technical name"oxylite". Mixed preparations of oxylitol are especially suitable for obtaining oxygen, which is released by them under the action of water. Cube-compressed oxylite can be used to obtain a uniform flow of oxygen in a conventional gas generating apparatus.

Na 2 O 2 + H 2 O \u003d 2NaOH + O 0 (atomic oxygen is released due to the decomposition of hydrogen peroxide).

Potassium superoxide ( KO 2) is often introduced into the composition of oxylite. Its interaction with carbon dioxide proceeds in this case according to the overall equation:

Na 2 O 2 + 2KO 2 + 2CO 2 \u003d Na 2 CO 3 + K 2 CO 3 + 2O 2 + 100 kcal, i.e. carbon dioxide is replaced by an equal volume of oxygen.

Capable of forming ozonides. The formation of potassium ozonide-KO 3 follows the equation:

4KOH + 3O 3 \u003d 4KO 3 + O 2 + 2H 2 O

It is a red crystalline substance and is the strongest oxidizing agent. During storage, KO 3 slowly decomposes according to the equation 2NaO 3 → 2NaO 2 + O 2 +11 kcal already under normal conditions. With water, it instantly decomposes according to the total scheme 4 KO 3 +2 H 2 O \u003d 4 KOH +5 O 2

Able to react with hydrogen, with the formation of ionic hydrides, according to the general scheme:

The interaction of hydrogen with heated alkali metals is slower than with alkaline earth metals. In the case of Li, heating up to 700–800°C is required, while its analogues already interact at 350–400°C. Alkali metal hydrides are very strong reducing agents. Their oxidation with air oxygen in the dry state is relatively slow, but in the presence of moisture, the process is so accelerated that it can lead to self-ignition of the hydride. This is especially true for the hydrides K, Rb, and Cs. A violent reaction occurs with water according to the scheme:

EN + H 2 O \u003d H 2 + EON

EH+O 2 →2EOH

When NaH or KH reacts with carbon dioxide, the corresponding formic acid salt is formed:

NaH+CO 2 →HCOONa

Capable of forming complexes

NaH+AlCl 3 →NaAlH 4 +3NaCl (sodium allanate)

NaAlH 4 → NaH+AlH 3

Normal alkali metal oxides (with the exception of Li 2 0) can be obtained only indirectly . They are solids of the following colors:

Na 2 O + 2HCl \u003d 2NaCl + H 2 O

Hydroxides (EOH) of alkali metals are colorless, highly hygroscopic substances that corrode most materials in contact with them. Hence their sometimes used in practice name - caustic alkalis. Under the action of alkalis, the skin of the human body swells greatly and becomes slippery; with a longer action, a very painful deep burn is formed. Caustic alkalis are especially dangerous for the eyes (it is recommended to work with protective glasses). Alkali that gets on your hands or dress should be immediately washed off with water, then moisten the affected area with a very dilute solution of some acid and rinse again with water.

All of them are relatively fusible and volatile without decomposition (except for LiOH, which splits off water). To obtain alkali metal hydroxides mainly using electrolytic methods. The largest production is sodium hydroxideelectrolysis concentrated water solution table salt:

2NaCl+2H 2 O→2NaOH+Cl 2 +H 2

Ø Are typical grounds:

NaOH+HCl=NaCl+H 2 O

2NaOH + CO 2 \u003d Na 2 CO 3 + H 2 O

2NaOH + 2NO 2 \u003d NaNO 3 + NaNO 2 + H 2 O

Ø Able to form complexes:

NaOH+ZnCl 2 = (ZnOH)Cl+NaCl

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

Al 2 O 3 + 6NaOH \u003d 2Na 3 AlO 3 + 3H 2 O

Al(OH) 3 +NaOH=Na

Ø Able to react with non-metals:

Cl 2 + 2KOH \u003d KCl + KClO + H 2 O (the reaction proceeds without heating)

Cl 2 + 6KOH \u003d 5KCl + KClO 3 + 3H 2 O (the reaction proceeds with heating)

3S + 6NaOH \u003d 2Na 2 S + Na 2 SO 3 + 3H 2 O

Ø They are used in organic synthesis (in particular, potassium and sodium hydroxide, sodium hydroxide is indicated in the examples):

NaOH + C 2 H 5 Cl \u003d NaCl + C 2 H 4 (method for obtaining alkenes, ethylene (ethene) in this case), an alcoholic solution of sodium hydroxide was used.

NaOH + C 2 H 5 Cl \u003d NaCl + C 2 H 5 OH(a method for obtaining alcohols, ethanol in this case), an aqueous solution of sodium hydroxide was used.

2NaOH + C 2 H 5 Cl \u003d 2NaCl + C 2 H 2 +H 2 O (method for obtaining alkynes, acetylene (ethine) in this case), an alcohol solution of sodium hydroxide was used.

C 6 H 5 OH (phenol) + NaOH \u003d C 6 H 5 ONa + H 2 O

NaOH (+ CaO) + CH 3 COONa → Na 2 CO 3 CH 4 (one of the ways to produce methane)

Ø You need to know the decomposition of several salts:

2KNO 3 →2KNO 2 + O 2

4KClO 3→ KCl+3KClO 4

2KClO 3→ KCl+3O 2

4Na 2 SO 3 →Na 2 S+3Na 2 SO 4

It is noteworthy that the decomposition of nitrates occurs approximately in the range of 450-600 ℃, then they melt without decomposition, but when they reach approximately 1000-1500 ℃, decomposition occurs according to the scheme:

4LiNO 2 →2Li 2 O+4NO+O 2

It is interesting:

K 4 [ Fe(CN) 6 ]+ FeCl 3 = KFe[ Fe(CN) 6 ]+3 KCl(qualitative response toFe3+)

3K 4 + 4FeCl 3 \u003d Fe 4 3 + 12KCl

Na 2 O 2 +2H 2 O \u003d 2NaOH + H 2 O 2

4NaO 2 +2H 2 O \u003d 4NaOH + 3O 2

4NaO 3 +2H 2 O \u003d 4NaOH + 5O 2 (reaction of ozonide sodium with water )

2NaO 3 → 2NaO 2 +O 2(The decomposition occurs at different temperatures, for example: the decomposition of sodium ozonide at -10 °C, cesium ozonide at +100°C)

NaNH 2 + H 2 O → NaOH + NH 3

Na 2 NH + 2H 2 O → 2NaOH + NH 3

Na 3 N + 3H 2 O → 3NaOH + NH 3

KNO 2 +2Al+KOH+5H 2 O→2K+NH 3

2NaI + Na 2 O 2 + 2H 2 SO 4 → I 2 ↓+ 2Na 2 SO 4 + 2H 2 O

Fe 3 O 4 + 4NaH \u003d 4NaOH + 3Fe

5NaN 3 + NaNO 3 → 8N 2 + 3Na 2 O

Application:

Sodium is widely used in the synthesis organic compounds and partly to obtain some of its derivatives. In nuclear technology, it is used as a coolant.

Lithium is of absolutely exceptional importance for thermonuclear technology. In the rubber industry, it is used in the production of artificial rubber (as a polymerization catalyst), in metallurgy - as a valuable additive to some other metals and alloys. For example, an additive of only hundredths of a percent of lithium greatly increases the hardness of aluminum and its alloys, and an additive of 0.4% lithium to lead almost triples its hardness without worsening bending resistance. There are indications that a similar cesium additive greatly improves the mechanical properties of magnesium and protects it from corrosion, but this is how it is used. Sodium hydride is sometimes used in metallurgy to isolate rare metals from their compounds. Its 2% solution in molten NaOH is used to remove scale from steel products (after a minute of exposure to it, the hot product is immersed in water, and recovered according to the equation

Fe 3 O 4 + 4NaH \u003d 4NaOH + 3Fe (scale disappears).

Schematic diagram of the factory installation for the production of soda by ammoniamethod (Solvay, 1863).

Limestone is calcined in the kiln (L), and the resulting CO 2 enters the carbonization tower (B), and CaO is quenched with water (C), after which Ca (OH) 2 is pumped into the mixer (D), where it meets with NH 4 Cl , and ammonia is released. The latter enters the absorber (D) and saturates there with a strong NaCl solution, which is then pumped into the carbonization tower, where NaHCO 3 and NH 4 Cl are formed when interacting with CO 2 . The first salt almost completely precipitates and lingers on the vacuum filter (E), and the second is again pumped into the mixer (D). Thus, NaCl and limestone are consumed all the time, and NaHCO 3 and CaCl 2 are obtained (the latter is in the form of production waste). The sodium bicarbonate is then converted into soda by heating.

Editor: Kharlamova Galina Nikolaevna

Alkali metals - common name elements of the 1st group of the periodic system chemical elements. Its composition is lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), and the hypothetical element ununenium (Uue). The name of the group comes from the name of soluble sodium and potassium hydroxides, which have the reaction and taste of alkali. Consider common features structures of atoms of elements, properties, production and use of simple substances.

Outdated and new group numbering

According to the outdated numbering system, alkali metals, occupying the leftmost vertical column of the periodic table, belong to I-A group. In 1989, the International Chemical Union (IUPAC) proposed a different option (long-period) as the main one. Alkali metals, in accordance with the new classification and continuous numbering, belong to the 1st group. The representative of the 2nd period, lithium, opens this set, and the radioactive element of the 7th period, francium, completes it. All metals of the 1st group have one s-electron in the outer shell of atoms, which they easily give up (recover).

The structure of alkali metal atoms

The elements of the 1st group are characterized by the presence of a second energy level, which repeats the structure of the previous inert gas. Lithium has 2 electrons on the penultimate layer, the rest have 8 electrons each. AT chemical reactions atoms easily donate an external s-electron, acquiring an energetically favorable configuration of a noble gas. Elements of the 1st group have small values ​​of ionization energy and electronegativity (EO). They easily form singly charged positive ions. In the transition from lithium to francium, the number of protons and electrons, the radius of the atom, increases. Rubidium, cesium and francium donate an outer electron more easily than the elements that precede them in the group. Consequently, in the group from top to bottom, the restorative capacity increases.

The easy oxidizability of alkali metals leads to the fact that the elements of the 1st group exist in nature in the form of compounds of their singly charged cations. Content in earth's crust sodium - 2.0%, potassium - 1.1%. Other elements in it are in small quantities, for example, francium reserves - 340 g. Sodium chloride is dissolved in sea ​​water, brine of salt lakes and estuaries, forms deposits of rock or table salt. Along with halite, sylvinite NaCl occurs. KCl and sylvin KCl. Feldspar is formed by potassium aluminosilicate K 2 . Sodium carbonate is dissolved in the water of a number of lakes, and the reserves of the element's sulfate are concentrated in the waters of the Caspian Sea (Kara-Bogaz-Gol). There are deposits of sodium nitrate in Chile (Chilean saltpeter). There is a limited number of naturally occurring lithium compounds. Rubidium and cesium are found as impurities in compounds of elements of the 1st group, and francium is found in the composition of uranium ores.

Alkali metal discovery sequence

The British chemist and physicist G. Davy in 1807 carried out the electrolysis of alkali melts, for the first time obtaining sodium and potassium in a free form. In 1817, the Swedish scientist Johann Arfvedson discovered the element lithium in minerals, and in 1825 G. Davy isolated the pure metal. Rubidium was first discovered in 1861 by R. Bunsen and G. Kirchhoff. German researchers analyzed the composition of aluminosilicates and obtained a red line in the spectrum corresponding to a new element. In 1939, an employee of the Paris Institute of Radioactivity, Marguerite Pere, established the existence of an isotope of francium. She also named the element in honor of her homeland. Ununennium (eca-francium) is the provisional name for a new type of atom with atomic number 119. The chemical symbol Uue is temporarily used. Researchers since 1985 have been trying to synthesize a new element, which will be the first in the 8th period, the seventh in the 1st group.

Physical properties of alkali metals

Almost all alkali metals are silvery white and have a metallic luster when freshly cut (cesium is golden yellow). In air, the luster fades, a gray film appears, on lithium it is greenish-black. This metal has the highest hardness among its neighbors in the group, but is inferior to talc, the softest mineral that opens the Mohs scale. Sodium and potassium are easily bent, they can be cut. Rubidium, cesium and francium in their pure form represent a pasty mass. The melting of alkali metals occurs at a relatively low temperature. For lithium, it reaches 180.54 °C. Sodium melts at 97.86°C, potassium at 63.51°C, rubidium at 39.32°C, and cesium at 28.44°C. The density of alkali metals is less than their related substances. Lithium floats in kerosene, rises to the surface of the water, potassium and sodium also float in it.

Crystal state

Crystallization of alkali metals occurs in the cubic syngony (body-centered). The atoms in its composition have a conduction band, on free levels which electrons can transfer. It is these active particles that carry out a special chemical bond- metal. The commonality of the structure of energy levels and the nature of crystal lattices explain the similarity of the elements of the 1st group. In the transition from lithium to cesium, the masses of the elements' atoms increase, which leads to a regular increase in density, as well as to a change in other properties.

Chemical properties of alkali metals

The only external electron in alkali metal atoms is weakly attracted to the nucleus, so they are characterized by low ionization energy, negative or close to zero electron affinity. Elements of the 1st group, having reducing activity, are practically incapable of oxidizing. In the group from top to bottom, activity in chemical reactions increases:

Production and use of alkali metals

Metals belonging to the 1st group are produced in industry by electrolysis of melts of their halides and other natural compounds. When decomposed by an electric current, positive ions at the cathode gain electrons and are reduced to free metal. The anion is oxidized at the opposite electrode.

During the electrolysis of hydroxide melts, OH particles are oxidized at the anode, oxygen is released and water is obtained. Another method is the thermal reduction of alkali metals from the melts of their salts with calcium. Simple substances and compounds of elements of the 1st group are of practical importance. Lithium serves as a raw material in nuclear power engineering and is used in rocket technology. In metallurgy, it is used to remove residuals of hydrogen, nitrogen, oxygen, and sulfur. Hydroxide supplement electrolyte in alkaline batteries.

Sodium is needed for nuclear energy, metallurgy, organic synthesis. Cesium and rubidium are used in the manufacture of solar cells. Hydroxides and salts, especially chlorides, nitrates, sulfates, carbonates of alkali metals, are widely used. Cations have biological activity, sodium and potassium ions are especially important for the human body.

Chemistry studies the properties of metals and non-metals. Did you know that there are alkaline and non-alkaline metals? And we not only know, but we will also give you a list for successful preparation in the subject of chemistry. So, the list of alkali metals is already given in the periodic table of Mendeleev. There, all the metals of the main subgroup in the first group are alkaline.

These are lithium, potassium, sodium, cesium, rubidium and francium. Only these metals are called alkaline. And they are called so because if they interact with water, then alkalis are formed as a result.

There is another type of metal - it is alkaline earth. If you want a list of only alkali metals, then there are only 6 metals. If all metals whose hydroxides have alkaline properties, then four more elements will enter - calcium, strontium, barium and radium.

It is difficult to find all alkali metals in their pure form in nature - after all, they easily enter into compounds. In particular, these metals are found in the form of these compounds.

Properties of alkali metals

Alkali metals are excellent conductors of heat, and they are also good conductors electricity.

Alkali metals have a low melting point

The density of metals increases with increasing number, but it becomes easier to melt them if the metals are at the bottom of the group.

Obtaining alkali metals

Usually alkali metals are obtained by electrolysis, however, two alkaline earth metals, strontium and barium, are obtained using the aluminothermic method.

Chemical properties

As we said, these metals are very active, they are also excellent reducing agents. They are found in the form of compounds in which the ionic bond will be the main one.

As a rule, they always form stable compounds. The main reactions and additional properties of alkali metals are given in the table:

So, now, using the list and table, as well as the periodic system of Mendeleev, you can tell a lot about alkali metals.

You can see what alkali metals look like. There is also a list and given bond reactions with water, sulfur, acids, salts and halogens.

Alkali metals are s-elements. On the outer electron layer, each of them has one electron (ns1). The radii of atoms from top to bottom in the subgroup increase, the ionization energy decreases, the reduction activity, as well as the ability to donate valence electrons from the outer layer, increases.

The metals under consideration are very active, therefore they are not found in nature in a free state. They can be found in the form of compounds, in the composition of minerals (common salt NaCl, sylvinite NaCl∙KCl, Glauber's salt NaSO4∙10H2O and others) or as ions in sea water.

Physical properties of alkali metals

All alkali metals are silvery white under normal conditions. crystalline substances with high thermal and electrical conductivity. They have body-centered cubic packing (BCP). The densities, boiling and melting points of group I metals are relatively low. From top to bottom in the subgroup, densities increase and melting points decrease.

Obtaining alkali metals

Alkali metals are usually obtained by electrolysis of molten salts (usually chlorides) or alkalis. During the electrolysis of a NaCl melt, for example, pure sodium is released at the cathode, and gaseous chlorine is released at the anode: 2NaCl (melt) \u003d 2Na + Cl2.

Chemical properties of alkali metals

By chemical properties lithium, sodium, potassium, rubidium, cesium and francium are the most active metals and one of the strongest reducing agents. In reactions, they easily donate electrons from the outer layer, turning into positively charged ions. In compounds formed by alkali metals, ionic bonds predominate.

When alkali metals interact with oxygen, peroxides are formed as the main product, and oxides as a by-product:

4Na+O2=2Na2O (sodium oxide).

With halogens they give halides, with sulfur - sulfides, with hydrogen - hydrides:

2Na+Cl2=2NaCl (sodium chloride),

2Na+S=Na2S (sodium sulfide),

2Na+H2=2NaH (sodium hydride).

Sodium hydride is an unstable compound. It decomposes with water, giving alkali and free hydrogen:

NaH+H2O=NaOH+H2.

Free hydrogen is also formed when alkali metals themselves interact with water:

2Na+2H2O=2NaOH+H2.

These metals also react with dilute acids, displacing hydrogen from them:

2Na+2HCl=2NaCl+H2.

Alkali metals react with organic halides by the Wurtz reaction.

What are alkali metals? These are elements of the first group, the main subgroup of the periodic system of elements of D. I. Mendeleev. These include such metals: Li, Na, K, Rb, Cs, Fr. They have a number of properties that are inherent in this group.

Peculiarities

These metals have small densities (lithium, sodium, potassium are lighter than water), low temperatures melting (the maximum for lithium is 180.6 ° C). They are soft, easy to cut with a knife, quickly oxidized, so they are stored in containers filled with chemically inactive gases or liquids (usually kerosene).

All metals of this subgroup have a silvery-white color. AT periodic system elements of D. I. Mendeleev, alkali metals always follow inert gases. Inert or noble gases enter into any chemical reactions very poorly, they are chemically inactive gases, and this is due to the fact that their electron shells are completely filled.

Unlike gases, alkali metals have one unpaired electron on the outer energy level. Therefore, in chemical reactions, these metals act as electron donors. They always have an oxidation state of +1, they are chemically very active - they actively react with acids (with an explosion), react violently with water, releasing hydrogen and forming alkalis MeOH (here Me is a metal). The activity of these metals increases from Li to Fr.

Lithium is the first element in the alkali metal group. The atomic mass is 6.941, it consists of two natural isotopes 6Li (7.5%) and 7Li (92.5%), it is also known to obtain artificially two more isotopes, but their life expectancy is very short.

An interesting fact about the alkali metal is that the cost of 7Li is several times higher than the cost of 6Li, although the former is more common. The history of the discovery of this element is associated with the name of the Swedish chemist I. A. Arfvedson.

Potassium, along with sodium, plays essential role in the work of cells of living organisms, maintaining their membrane potential. The human body contains about 175 grams of this metal, and to maintain this supply, it needs to be replenished by about 4 grams daily.

In nature, it is often found, but only in the composition of compounds, it ranks third in terms of the amount of its content in water. With a deficiency in the soil, this metal is introduced in the form of fertilizers: potassium chloride KCl, potassium sulfate K2SO4 and plant ash.

Many people know such a substance as potassium cyanide; but not many people know where it is used. And they use it for galvanic silvering as well as gilding base metals, extracting expensive metals, namely silver and gold, from ores.

Cesium was discovered in 1860 in the healing mineral springs of the Black Forest. The atomic mass is 132.905.

This metal is used in such industries: automation and electronics, in radar and cinema, as well as in nuclear reactors and spaceships. It was the first element to be discovered using spectral analysis.

France

Francium is the most unstable and heaviest element among the alkali metals, with an atomic mass of 223 and a half-life of 22 minutes. Because of these characteristics, it was very difficult to distinguish it.

This is a very rare metal of which, according to scientists, there are only about 500 grams in the earth's crust, so francium was studied on artificially created samples.

Sodium

Sodium is one of the most common alkali metals. Because of this, it is used in a variety of industries. For example, precious metal ores are treated with sodium cyanide solution. As a result, coordination compounds are obtained from which pure gold or silver is isolated with the help of zinc.

Sodium is also used as a coolant in nuclear submarines due to some of its physical properties (big difference between melting and boiling points). In nature, sodium is not found in its pure form - it is too active, therefore - only in the composition of ores.

An interesting fact is that a layer of atomic sodium was found in the atmosphere at an altitude of about 80 km. This is due to the fact that at such heights there are no elements with which sodium could interact.

Rubidium

Rubidium is an interesting alkali metal in its own way. Having atomic mass 85,467 the metal is radioactive. In contact with air, rubidium ignites and burns with a pinkish-violet flame, with water, F, Cl, Br, I, S - an explosion occurs.

An interesting feature of rubidium is the ability to generate electric current under the influence of solar radiation.

Although the alkali metals have a number of features that are common to all of them, each of them also has properties that are unique to it. Some elements are still very poorly understood, and given the demand for metals of this group by various industries, it is long overdue to fill in the blanks in scientific reference books.