Message about sodium. Is sodium a metal or a non-metal? Basic properties and characteristics of sodium. Being in nature

Is sodium a metal or a non-metal? It is a mistake to believe that the second option. Sodium is a soft, silvery-white metal that appears on the periodic table at atomic number 11.

Moreover, it (or rather its compounds) has been known since ancient times! Even the Bible mentions sodium as an ingredient in cleaning products. However, this is a historical note, albeit an interesting one. Now it’s worth talking about the features of this element and its other characteristics.

Physical properties

So, the answer to the question “Is sodium a metal or a non-metal?” very clear. Even just looking at this substance, you can understand everything. It is obvious that Which, by the way, although it has a silvery-white color, has a violet tint in thin layers.

This is a very plastic substance. Soft metals are those that can be forged without much effort and are also characterized by ductility and fusibility. But in relation to sodium, this word can be applied in the literal sense. It can be cut with a knife without effort. By the way, a fresh cut shines very brightly. Other properties include:

• Density. Under normal conditions - 0.971 g/cm³.
• The melting and boiling points are 97.81 °C and 882.95 °C, respectively.
• Molar heat capacity - 28.23 J/(K.mol).
• The specific heat of fusion and evaporation is 2.64 kJ/mol and 97.9 kJ/mol, respectively.
• Molar volume - 23.7 cm³/mol.

It is worth noting that under pressure, sodium (Na) turns red and transparent. In this state, this metal is very similar to ruby.

If you place it at room temperature, it forms crystals in cubic symmetry. However, by lowering it to −268 °C, you can see how the metal transforms into the hexagonal phase. To understand what we are talking about, just remember graphite. This is a prime example of a hexagonal crystal.

Oxidation and combustion

Now we can move on to the chemical properties of sodium (Na). This alkali metal, when exposed to air, easily oxidizes. As a result, sodium oxide (Na 2 O) is formed. It looks like colorless cubic crystals. This is a salt-forming binary inorganic substance that is used as a reagent in the synthesis process. It is used to make sodium hydroxide and other compounds.

Therefore, to protect the metal from oxygen exposure, it is stored in kerosene.

But during combustion, sodium peroxide (Na 2 O 2) is formed. They look like white-yellow crystals, which are characterized by vigorous interaction with water, accompanied by the release of heat. Na 2 O 2 is used for bleaching silk, wool, fabrics, straw, viscose and wood pulp.

Reactions with water

The silvery-white soft metal sodium also interacts successfully with H2O. The reaction with water is very violent. A small piece of sodium placed in this liquid floats to the surface and begins to melt due to the heat generated. As a result, it turns into a white ball, which moves quickly along the surface of the water in different directions.

This very spectacular reaction is accompanied by the release of hydrogen. When conducting such an experiment, care must be taken as it may ignite. And everything happens according to the following equation: 2Na + 2H 2 O → 2NaOH + H 2.

Interactions with nonmetals

Sodium is a metal, it can also be called a strong reducing agent, which it is. Like other alkaline substances, however. So it reacts vigorously with many nonmetals other than carbon, iodine, and noble gases, which include radioactive radon, krypton, neon, xenon, argon, and helium. Such reactions look like this: 2Na + Cl 2 → 2NaCl. Or here’s another example: 2Na + H 2 → 250-450 °C 2NaH.

It is worth noting that sodium is more active than lithium. In principle, it can react with nitrogen, but very poorly (in a glow discharge). As a result of this interaction, an unstable substance called sodium nitride is formed. These are dark gray crystals that react with water and decompose when heated. They are formed according to the equation: 6Na + N 2 → 2Na 3 N.

Reactions with acids

They should also be listed, talking about the chemical characteristics of sodium. This substance reacts with dilute acids like an ordinary metal. It looks like this: 2Na + 2HCl → 2NaCl + H2.

Sodium interacts differently with concentrated substances that are characterized by oxidative reactions; such reactions are accompanied by the release of reduction products. Here is an example of a formula: 8Na + 10NHO 3 → 8NaNO 3 + 3H 2 O.

It is also worth noting that the alkali metal sodium easily dissolves in liquid ammonia (NH 3), a 10% solution of which is well known to everyone as ammonia. The equation looks like this: Na + 4NH3 → - 40°C Na 4. As a result of this reaction, a blue solution is formed.

The metal also interacts with gaseous ammonia, but when heated. This reaction looks like this: 2Na + 2NH3 → 35 0°C 2NaNH 2 + H 2.

Other connections

When listing the main properties of sodium, it is also worth mentioning that it can interact with mercury, a unique element that under normal conditions is a white-silver heavy liquid, while being a metal.

As a result of this reaction, an alloy is formed. Its exact name is sodium amalgam. This substance is used as a reducing agent, its properties being softer than pure metal. If you heat it with potassium, you get a liquid alloy.

This metal can also dissolve in so-called crown ethers - macroheterocyclic compounds, but only in the presence of organic solvents. As a result of this reaction, an alkalide (a salt, a strong reducing agent) or an electride (a blue solvent) is formed.

It is also impossible not to mention that alkyl halides, which are halogen-carbon substances, with excess sodium give organosodium compounds. In air they usually ignite spontaneously. And in water they explode.

Application

The properties and characteristics of sodium allow it to be widely used in industry, metallurgy and preparative chemistry as a powerful reducing agent. In addition, this substance is involved:

• In the drying of organic solvents.
• In the production of sulfur-sodium batteries.
• In exhaust valves of truck engines. Plays the role of a liquid heat sink.
• In the manufacture of electrical wires that are designed for high currents.
• In alloys with cesium, rubidium and potassium. Together with these substances, sodium forms a highly efficient coolant, which, by the way, is used for fast neutrons in nuclear reactors.
• In gas discharge lamps.

And these are just some of the areas of its application. But the most common substance in the world is sodium chloride. It is found in almost every home, because it is table salt.

It is also impossible not to mention that the earth’s crust consists of 2.6% sodium. And in general, it is in 7th place in the ranking of the most common elements in nature and in 5th place in the list of the most common metals. It is impossible to find sodium in nature in its pure form, since it is chemically active, but it is found in huge quantities in the form of sulfate, carbonate, nitrate and chloride.

Biological role

So, all the basics on the topic “Is sodium a metal or a non-metal?” it was said. Finally, a few words about the biological role of this substance.

Sodium is an integral part of any living organism. Human is no exception. Here are his roles:

• Maintains osmotic pressure.
• Transports carbon dioxide.
• Normalizes water balance.
• Promotes the transport of glucose, amino acids, anions through cell membranes.
• Its exchange with potassium ions influences the formation of the action potential.
• Positively affects protein metabolism.
• Takes part in the hydration process.

Sodium is included in almost all products. But its main sources are salt and baking soda. Vitamin D improves the absorption of this substance.

Sodium deficiency does not occur, but problems associated with consuming insufficient amounts can occur during fasting. This is fraught with weight loss, vomiting, impaired absorption of monosaccharides, and the formation of gases in the gastrointestinal tract. In especially severe cases, neuralgia and convulsions occur. Therefore, it is better not to subject your body to severe starvation.

Sodium is a chemical element belonging to the first group of the periodic table of elements created by D.I. Mendeleev.

Sodium has atomic number 11 and its atomic weight is 22.99. Sodium is so soft that it can be cut with a knife. Its density (at 20°C) is 0.968 g/cm3. Has a melting point of about 98° C; and the boiling point of sodium is 883° C.

Sodium is a reactive and very active element; When stored in open air, it oxidizes very easily to form sodium carbonate and sodium oxide hydrate.

Sodium can form alloys with many metals, which are of great technical importance in science and production. Sodium and its alloys are widely used in many industrial sectors. In the chemical industry, sodium is used to produce sodium peroxide, tetraethyl lead (via the Na - Pb alloy), sodium cyanide, sodium hydride, detergents, etc.

In the metallurgical industry, sodium is used as a reducing agent in the production of thorium, uranium, titanium, zirconium and other metals from their fluoride compounds or chlorides. Sodium in liquid form, as well as its alloys with potassium, are used in nuclear energy as a coolant.

It is not surprising that sodium is one of the most common chemical elements in nature. According to various estimates, its content in the earth's crust reaches 2.27%. Even in living organisms it is contained in amounts up to 0.02%. Although sodium belongs to the group of metals, it is not found in nature in its pure form due to its high chemical activity. Most often it is found in the form of chloride NaCl (rock salt, halite), as well as nitrate NaNO3 (saltpeter), carbonate Na2CO3 NaHCO3 2H2O (trona), sulfate Na2SO4 10H2O (mirabilite), Na2B4O7 4H2O (kernite), tetraborate Na2B4O7 10 H2O (borax ) and other salts. Naturally, ocean waters contain huge reserves of sodium chloride.

In the food industry, it is table salt, which is very necessary for cooking; in the chemical industry, it is used to produce mineral fertilizers and antiseptics, and in light industry, sodium is used to treat leather. It is also widely used in metallurgical production, in the manufacture of gas-discharge lamps, and in the form of an alloy with potassium it is used as a refrigerant.

Without the use of its compounds (sodium formate and sodium fluoride), the development of the modern construction industry is impossible today; Since they are both an antifreeze agent and an excellent plasticizer in the production of high-quality concrete and various products made from it, construction work can be carried out at very low temperatures.

Sodium is often used as a coolant; an alloy of sodium with potassium is used in nuclear energy to operate nuclear installations. As a reducing agent, it is used to produce refractory metals (zirconium, titanium, etc.); as a catalyst, it is used in the production of synthetic rubber and in organic synthesis. Other sodium compounds are also very widely used:

• • sodium hydroxide NaOH is one of the most important production components of the chemical industry, which is used in the purification of petroleum products, in the production of artificial fiber, in paper, textile, soap and other industries;
  • sodium peroxide Na2O2 - used for bleaching fabrics, silk, wool, etc.

With all acids, Sodium forms salts, which are often used in human life and in almost all industries:

• • sodium bromide NaBr - in photography and medicine;
  • sodium fluoride NaF - for wood processing, in agriculture, in the production of enamels, etc.;
  • soda ash (Na2CO3 sodium carbonate) and drinking soda (NaHCO3 sodium bicarbonate) are the main products of the chemical industry;
  • sodium dichromate Na2Cr2O7 - used as a tannin and a strong oxidizing agent (chromic mixture - a solution of concentrated sulfuric acid and sodium dichromate - used for washing laboratory glassware);

• • sodium chloride NaCl (table salt) - in the food industry, technology, medicine, for the production of caustic soda, soda, etc.;
  • sodium nitrate NaNO3 (sodium nitrate) - nitrogen fertilizer;
  • sodium sulfate Na2SO4 - indispensable in the leather, soap, glass, pulp and paper, textile industries;
  • sodium sulfite Na2SO4 with sodium thiosulfate Na2SO3 - used in medicine and photography, etc.
  • sodium silicate NaSiO3 is a soluble glass;

The price of sodium on the world market is not high. This situation occurs due to the very wide distribution of sodium and its compounds in nature, as well as the relatively inexpensive methods of its industrial production. Sodium in the form of pure metal is industrially obtained from molten sodium hydroxide or chloride by passing a large electric current through it. Today, the global consumption of sodium and its compounds amounts to more than 100 million tons, and the demand for it is increasing every year. It is difficult to name an industry where sodium is not used.

The content of the article

SODIUM– (Natrium) Na, a chemical element of group 1 (Ia) of the Periodic Table, belongs to the alkaline elements. Atomic number 11, relative atomic mass 22.98977. In nature there is one stable isotope 23 Na. Six radioactive isotopes of this element are known, two of which are of interest to science and medicine. Sodium-22, with a half-life of 2.58 years, is used as a source of positrons. Sodium-24 (its half-life is about 15 hours) is used in medicine for the diagnosis and treatment of some forms of leukemia.

Oxidation state +1.

Sodium compounds have been known since ancient times. Sodium chloride is an essential component of human food. It is believed that people began to use it in the Neolithic, i.e. about 5–7 thousand years ago.

The Old Testament mentions a substance called “neter.” This substance was used as a detergent. Most likely, neter is soda, a sodium carbonate that formed in the salty Egyptian lakes with calcareous shores. The Greek authors Aristotle and Dioscorides later wrote about the same substance, but under the name “nitron,” and the ancient Roman historian Pliny the Elder, mentioning the same substance, called it “nitrum.”

In the 18th century Chemists already knew a lot of different sodium compounds. Sodium salts were widely used in medicine, in tanning leather, and in dyeing fabrics.

Metallic sodium was first obtained by the English chemist and physicist Humphry Davy by electrolysis of molten sodium hydroxide (using a voltaic column of 250 pairs of copper and zinc plates). The name "sodium" chosen by Davy for this element reflects its origin from the soda Na 2 CO 3 . The Latin and Russian names of the element are derived from the Arabic “natrun” (natural soda).

Distribution of sodium in nature and its industrial extraction.

Sodium is the seventh most abundant element and the fifth most abundant metal (after aluminum, iron, calcium and magnesium). Its content in the earth's crust is 2.27%. Most of the sodium is found in various aluminosilicates.

Huge deposits of sodium salts in relatively pure form exist on all continents. They are the result of the evaporation of ancient seas. This process is still ongoing in Salt Lake (Utah), the Dead Sea and other places. Sodium is found in the form of NaCl chloride (halite, rock salt), as well as carbonate Na 2 CO 3 NaHCO 3 2H 2 O (trona), nitrate NaNO 3 (saltpeter), sulfate Na 2 SO 4 10H 2 O (mirabilite) , tetraborate Na 2 B 4 O 7 10 H 2 O (borax) and Na 2 B 4 O 7 4H 2 O (kernite) and other salts.

There are inexhaustible reserves of sodium chloride in natural brines and ocean waters (about 30 kg m–3). It is estimated that rock salt in an amount equivalent to the sodium chloride content in the World Ocean would occupy a volume of 19 million cubic meters. km (50% more than the total volume of the North American continent above sea level). A prism of this volume with a base area of ​​1 sq. km can reach the Moon 47 times.

Now the total production of sodium chloride from seawater has reached 6–7 million tons per year, which is about a third of the total world production.

Living matter contains an average of 0.02% sodium; There is more of it in animals than in plants.

Characteristics of a simple substance and industrial production of sodium metal.

Sodium is a silvery-white metal, in thin layers with a purple tint, plastic, even soft (easily cut with a knife), a fresh cut of sodium is shiny. The values ​​of electrical conductivity and thermal conductivity of sodium are quite high, the density is 0.96842 g/cm 3 (at 19.7 ° C), the melting point is 97.86 ° C, the boiling point is 883.15 ° C.

The ternary alloy, containing 12% sodium, 47% potassium and 41% cesium, has the lowest melting point for metal systems, equal to –78 ° C.

Sodium and its compounds color the flame bright yellow. The double line in the sodium spectrum corresponds to transition 3 s 1–3p 1 in the atoms of the element.

The chemical activity of sodium is high. In air, it quickly becomes covered with a film of a mixture of peroxide, hydroxide and carbonate. Sodium burns in oxygen, fluorine and chlorine. When a metal is burned in air, Na 2 O 2 peroxide is formed (with an admixture of Na 2 O oxide).

Sodium reacts with sulfur when ground in a mortar and reduces sulfuric acid to sulfur or even sulfide. Solid carbon dioxide (“dry ice”) explodes on contact with sodium (carbon dioxide fire extinguishers cannot be used to extinguish a sodium fire!). With nitrogen, the reaction occurs only in an electrical discharge. Sodium does not interact only with inert gases.

Sodium reacts actively with water:

2Na + 2H 2 O = 2NaOH + H 2

The heat released during the reaction is enough to melt the metal. Therefore, if a small piece of sodium is thrown into water, it melts due to the thermal effect of the reaction and a drop of metal, which is lighter than water, “runs” along the surface of the water, driven by the reactive force of the released hydrogen. Sodium reacts much more calmly with alcohols than with water:

2Na + 2C 2 H 5 OH = 2C 2 H 5 ONa + H 2

Sodium readily dissolves in liquid ammonia to form bright blue metastable solutions with unusual properties. At –33.8° C, up to 246 g of sodium metal dissolves in 1000 g of ammonia. Dilute solutions are blue, concentrated solutions are bronze. They can be stored for about a week. It has been established that in liquid ammonia, sodium ionizes:

Na Na + + e –

The equilibrium constant of this reaction is 9.9·10 –3. The leaving electron is solvated by ammonia molecules and forms a complex -. The resulting solutions have metallic electrical conductivity. When ammonia evaporates, the original metal remains. When the solution is stored for a long time, it gradually becomes discolored due to the reaction of the metal with ammonia to form the amide NaNH 2 or imide Na 2 NH and the release of hydrogen.

Sodium is stored under a layer of dehydrated liquid (kerosene, mineral oil) and transported only in sealed metal containers.

The electrolytic method for the industrial production of sodium was developed in 1890. Electrolysis was carried out on molten sodium hydroxide, as in Davy's experiments, but using more advanced energy sources than the voltaic column. In this process, along with sodium, oxygen is released:

anode (nickel): 4OH – – 4e – = O 2 + 2H 2 O.

During the electrolysis of pure sodium chloride, serious problems arise, associated, firstly, with the close melting point of sodium chloride and the boiling point of sodium and, secondly, with the high solubility of sodium in liquid sodium chloride. Adding potassium chloride, sodium fluoride, calcium chloride to sodium chloride allows you to reduce the melt temperature to 600° C. Production of sodium by electrolysis of a molten eutectic mixture (an alloy of two substances with the lowest melting point) 40% NaCl and 60% CaCl 2 at ~580° C in a cell developed by the American engineer G. Downs, it was started in 1921 by DuPont near the power plant at Niagara Falls.

The following processes occur on the electrodes:

cathode (iron): Na + + e – = Na

Ca 2+ + 2e – = Ca

anode (graphite): 2Cl – – 2e – = Cl 2.

Sodium and calcium metals form on a cylindrical steel cathode and are lifted up by a cooled tube in which the calcium solidifies and falls back into the melt. Chlorine generated at the central graphite anode is collected under the nickel roof and then purified.

Currently, the production volume of sodium metal is several thousand tons per year.

The industrial use of sodium metal is due to its strong reducing properties. For a long time, most of the metal produced was used to produce tetraethyl lead PbEt 4 and tetramethyl lead PbMe 4 (anti-knock agents for gasoline) by reacting alkyl chlorides with an alloy of sodium and lead at high pressure. Now this production is rapidly declining due to environmental pollution.

Another area of ​​application is the production of titanium, zirconium and other metals by reducing their chlorides. Smaller amounts of sodium are used to produce compounds such as hydride, peroxide and alcoholates.

Dispersed sodium is a valuable catalyst in the production of rubber and elastomers.

There is increasing use of molten sodium as a heat exchange fluid in fast neutron nuclear reactors. Sodium's low melting point, low viscosity, small neutron absorption cross section, combined with extremely high heat capacity and thermal conductivity, make it (and its alloys with potassium) an indispensable material for these purposes.

Sodium reliably cleans transformer oils, ethers and other organic substances from traces of water, and with the help of sodium amalgam you can quickly determine the moisture content in many compounds.

Sodium compounds.

Sodium forms a complete set of compounds with all the usual anions. It is believed that in such compounds there is almost complete separation of charge between the cationic and anionic parts of the crystal lattice.

Sodium oxide Na 2 O is synthesized by the reaction of Na 2 O 2, NaOH, and most preferably NaNO 2, with sodium metal:

Na 2 O 2 + 2Na = 2Na 2 O

2NaOH + 2Na = 2Na2O + H2

2NaNO 2 + 6Na = 4Na 2 O + N 2

In the last reaction, sodium can be replaced with sodium azide NaN 3:

5NaN 3 + NaNO 2 = 3Na 2 O + 8N 2

It is best to store sodium oxide in anhydrous gasoline. It serves as a reagent for various syntheses.

Sodium peroxide Na 2 O 2 in the form of a pale yellow powder is formed during the oxidation of sodium. In this case, under conditions of limited supply of dry oxygen (air), Na 2 O oxide is first formed, which then turns into Na 2 O 2 peroxide. In the absence of oxygen, sodium peroxide is thermally stable up to ~675°C.

Sodium peroxide is widely used in industry as a bleaching agent for fibers, paper pulp, wool, etc. It is a strong oxidizing agent: it explodes when mixed with aluminum powder or charcoal, reacts with sulfur (and becomes hot), and ignites many organic liquids. Sodium peroxide reacts with carbon monoxide to form carbonate. The reaction of sodium peroxide with carbon dioxide releases oxygen:

2Na 2 O 2 + 2CO 2 = 2Na 2 CO 3 + O 2

This reaction has important practical applications in breathing apparatus for submariners and firefighters.

Sodium superoxide NaO 2 is obtained by slowly heating sodium peroxide at 200–450° C under an oxygen pressure of 10–15 MPa. Evidence of the formation of NaO 2 was first obtained in the reaction of oxygen with sodium dissolved in liquid ammonia.

The action of water on sodium superoxide leads to the release of oxygen even in the cold:

2NaO 2 + H 2 O = NaOH + NaHO 2 + O 2

As the temperature rises, the amount of oxygen released increases as the resulting sodium hydroperoxide decomposes:

4NaO 2 + 2H 2 O = 4NaOH + 3O 2

Sodium superoxide is a component of systems for air regeneration in confined spaces.

Sodium ozonide NaO 3 is formed by the action of ozone on anhydrous sodium hydroxide powder at low temperature, followed by extraction of red NaO 3 with liquid ammonia.

Sodium hydroxide NaOH is often called caustic soda or caustic soda. This is a strong base and is classified as a typical alkali. Numerous NaOH hydrates have been obtained from aqueous solutions of sodium hydroxide n H 2 O, where n= 1, 2, 2.5, 3.5, 4, 5.25 and 7.

Sodium hydroxide is very aggressive. It destroys glass and porcelain due to interaction with the silicon dioxide they contain:

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

The name "caustic soda" reflects the corrosive effect of sodium hydroxide on living tissue. Getting this substance into the eyes is especially dangerous.

The Duke of Orleans' physician, Nicolas Leblanc (1742–1806), developed a convenient process for producing sodium hydroxide from NaCl in 1787 (patent 1791). This first large-scale industrial chemical process was a major technological achievement in Europe in the 19th century. The Leblanc process was later superseded by the electrolytic process. In 1874, world production of sodium hydroxide amounted to 525 thousand tons, of which 495 thousand tons were obtained by the Leblanc method; by 1902, the production of sodium hydroxide reached 1800 thousand tons, but only 150 thousand tons were obtained using the Leblanc method.

Today, sodium hydroxide is the most important alkali in industry. Annual production in the USA alone exceeds 10 million tons. It is obtained in huge quantities by electrolysis of brines. When a solution of sodium chloride is electrolyzed, sodium hydroxide is formed and chlorine is released:

cathode (iron) 2H 2 O + 2 e– = H 2 + 2OH –

anode (graphite) 2Cl – – 2 e– = Cl 2

Electrolysis is accompanied by the concentration of alkali in huge evaporators. The largest in the world (at the PPG Inductries "Lake Charles plant) has a height of 41 m and a diameter of 12 m. About half of the sodium hydroxide produced is used directly in the chemical industry to produce various organic and inorganic substances: phenol, resorcinol, b-naphthol, sodium salts (hypochlorite, phosphate, sulfide, aluminates). In addition, sodium hydroxide is used in the production of paper and pulp, soap and detergents, oils, textiles. An important area of ​​application of sodium hydroxide is the neutralization of acids.

Sodium chloride NaCl is known as table salt and rock salt. It forms colorless, slightly hygroscopic cubic crystals. Sodium chloride melts at 801° C, boils at 1413° C. Its solubility in water depends little on temperature: 35.87 g of NaCl dissolves in 100 g of water at 20° C, and 38.12 g at 80° C.

Sodium chloride is a necessary and indispensable seasoning for food. In the distant past, salt was equal in price to gold. In ancient Rome, legionnaires were often paid not in money, but in salt, hence the word soldier.

In Kievan Rus they used salt from the Carpathian region, from salt lakes and estuaries on the Black and Azov Seas. It was so expensive that at ceremonial feasts it was served on the tables of noble guests, while others went away “slurping.”

After the annexation of the Astrakhan region to the Moscow state, the Caspian lakes became important sources of salt, and still there was not enough of it, it was expensive, so there was discontent among the poorest sections of the population, which grew into an uprising known as the Salt Riot (1648)

In 1711 Peter I issued a decree introducing a salt monopoly. Trade in salt became the exclusive right of the state. The salt monopoly lasted for more than a hundred and fifty years and was abolished in 1862.

Nowadays sodium chloride is a cheap product. Together with coal, limestone and sulfur, it is one of the so-called “big four” mineral raw materials, the most essential for the chemical industry.

Most sodium chloride is produced in Europe (39%), North America (34%) and Asia (20%), while South America and Oceania each account for only 3% and Africa 1%. Rock salt forms vast underground deposits (often hundreds of meters thick) that contain more than 90% NaCl. A typical Cheshire salt deposit (the main source of sodium chloride in Great Britain) covers an area of ​​60 × 24 km and has a salt bed of about 400 m thick. This deposit alone is estimated to be worth more than 10 11 tons.

World salt production by the beginning of the 21st century. reached 200 million tons, 60% of which is consumed by the chemical industry (for the production of chlorine and sodium hydroxide, as well as paper pulp, textiles, metals, rubbers and oils), 30% by the food industry, 10% by other fields of activity. Sodium chloride is used, for example, as a cheap deicing agent.

Sodium carbonate Na 2 CO 3 is often called soda ash or simply soda. It is found in nature in the form of ground brines, brine in lakes and the minerals natron Na 2 CO 3 ·10H 2 O, thermonatrite Na 2 CO 3 ·H 2 O, trona Na 2 CO 3 ·NaHCO 3 ·2H 2 O. Sodium forms and other various hydrated carbonates, bicarbonates, mixed and double carbonates, for example Na 2 CO 3 7H 2 O, Na 2 CO 3 3NaHCO 3, aKCO 3 n H 2 O, K 2 CO 3 NaHCO 3 2H 2 O.

Among the salts of alkali elements obtained industrially, sodium carbonate is of greatest importance. Most often, the method developed by the Belgian chemist-technologist Ernst Solvay in 1863 is used for its production.

A concentrated aqueous solution of sodium chloride and ammonia is saturated with carbon dioxide under slight pressure. In this case, a precipitate of relatively poorly soluble sodium bicarbonate is formed (the solubility of NaHCO 3 is 9.6 g per 100 g of water at 20 ° C):

NaCl + NH 3 + H 2 O + CO 2 = NaHCO 3 Ї + NH 4 Cl

To obtain soda, sodium bicarbonate is calcined:

The carbon dioxide released is returned to the first process. Additional carbon dioxide is obtained by calcining calcium carbonate (limestone):

The second product of this reaction, calcium oxide (lime), is used to regenerate ammonia from ammonium chloride:

Thus, the only by-product of soda production using the Solvay method is calcium chloride.

Overall process equation:

2NaCl + CaCO 3 = Na 2 CO 3 + CaCl 2

Obviously, under normal conditions in an aqueous solution the reverse reaction occurs, since the equilibrium in this system is completely shifted from right to left due to the insolubility of calcium carbonate.

Soda ash obtained from natural raw materials (natural soda ash) is of better quality compared to soda produced by the ammonia method (chloride content less than 0.2%). In addition, specific capital investments and the cost of soda from natural raw materials are 40–45% lower than those obtained synthetically. About a third of the world's soda production now comes from natural deposits.

World production of Na 2 CO 3 in 1999 was distributed as follows:

The world's largest producer of natural soda ash is the USA, where the largest explored reserves of trona and brine of soda lakes are concentrated. The deposit in Wyoming forms a layer 3 m thick and an area of ​​2300 km 2. Its reserves exceed 10 10 tons. In the USA, the soda industry is focused on natural raw materials; the last soda synthesis plant was closed in 1985. Production of soda ash in the United States has stabilized at 10.3–10.7 million tons in recent years.

Unlike the United States, most countries in the world depend almost entirely on the production of synthetic soda ash. China ranks second in the world in soda ash production after the United States. The production of this chemical in China in 1999 reached approximately 7.2 million tons. The production of soda ash in Russia in the same year amounted to about 1.9 million tons.

In many cases, sodium carbonate is interchangeable with sodium hydroxide (for example, in the production of paper pulp, soap, cleaning products). About half of the sodium carbonate is used in the glass industry. One growing application is the removal of sulfur contaminants from gas emissions from power generation plants and large furnaces. Sodium carbonate powder is added to the fuel, which reacts with sulfur dioxide to form solid products, particularly sodium sulfite, which can be filtered or precipitated.

Sodium carbonate was previously widely used as "washing soda", but this application has now disappeared due to the use of other household detergents.

Sodium bicarbonate NaHCO 3 (baking soda) is used mainly as a source of carbon dioxide in baking bread, making confectionery, producing carbonated drinks and artificial mineral waters, as a component of fire extinguishing compounds and as a medicine. This is due to the ease of its decomposition at 50–100° C.

Sodium sulfate Na 2 SO 4 occurs in nature in anhydrous form (thenardite) and in the form of decahydrate (mirabilite, Glauber's salt). It is part of astrachonite Na 2 Mg(SO 4) 2 4H 2 O, vanthoffite Na 2 Mg(SO 4) 2, glauberite Na 2 Ca(SO 4) 2. The largest reserves of sodium sulfate are in the CIS countries, as well as in the USA, Chile, and Spain. Mirabilite, isolated from natural deposits or brine of salt lakes, is dehydrated at 100 ° C. Sodium sulfate is also a by-product of the production of hydrogen chloride using sulfuric acid, as well as the end product of hundreds of industrial processes that use neutralization of sulfuric acid with sodium hydroxide.

Data on the production of sodium sulfate are not published, but global production of the natural raw material is estimated to be about 4 million tons per year. The recovery of sodium sulfate as a by-product is estimated globally at 1.5–2.0 million tons.

For a long time, sodium sulfate was little used. Now this substance is the basis of the paper industry, since Na 2 SO 4 is the main reagent in kraft pulping for the preparation of brown wrapping paper and corrugated cardboard. Wood shavings or sawdust are processed in a hot alkaline solution of sodium sulfate. It dissolves lignin (the component of wood that holds the fibers together) and releases the cellulose fibers, which are then sent to paper making machines. The remaining solution is evaporated until it is capable of burning, providing steam for the plant and heat for evaporation. Molten sodium sulfate and hydroxide are flame resistant and can be reused.

A smaller portion of sodium sulfate is used in the production of glass and detergents. The hydrated form of Na 2 SO 4 ·10H 2 O (Glauber's salt) is a laxative. It is used less now than before.

Sodium nitrate NaNO 3 is called sodium or Chilean nitrate. The large deposits of sodium nitrate found in Chile appear to have been formed by the biochemical decomposition of organic remains. The ammonia released initially was probably oxidized to nitrous and nitric acids, which then reacted with dissolved sodium chloride.

Sodium nitrate is obtained by the absorption of nitrous gases (a mixture of nitrogen oxides) with a solution of sodium carbonate or hydroxide, or by the exchange interaction of calcium nitrate with sodium sulfate.

Sodium nitrate is used as a fertilizer. It is a component of liquid salt refrigerants, quenching baths in the metalworking industry, and heat-storing compositions. A ternary mixture of 40% NaNO 2, 7% NaNO 3 and 53% KNO 3 can be used from the melting point (142° C) to ~600° C. Sodium nitrate is used as an oxidizing agent in explosives, rocket fuels, and pyrotechnic compositions. It is used in the production of glass and sodium salts, including nitrite, which serves as a food preservative.

Sodium nitrite NaNO 2 can be obtained by thermal decomposition of sodium nitrate or its reduction:

NaNO 3 + Pb = NaNO 2 + PbO

For the industrial production of sodium nitrite, nitrogen oxides are absorbed by an aqueous solution of sodium carbonate.

Sodium nitrite NaNO 2, in addition to being used with nitrates as heat-conducting melts, is widely used in the production of azo dyes, for corrosion inhibition and meat preservation.

Elena Savinkina

Lecture outline:

1. Distribution of sodium in nature.

2. Historical background.

3. Physical properties of sodium

4. 4.Chemical properties of sodium

5. Obtaining sodium.

6. 6.Obtaining sodium.

Sodium(Natrium), Na, chemical element of group I of the periodic system of Mendeleev: atomic number 11, atomic mass 22.9898; a silvery-white soft metal that quickly oxidizes from the surface in air. The natural element consists of one stable isotope, 23 Na.

Historical reference. Natural compounds of Sodium - table salt NaCl, soda Na 2 CO 3 - have been known since ancient times. The name "Sodium" comes from the Arabic natrun, Greek. nitron, originally referred to natural soda. Already in the 18th century, chemists knew many other sodium compounds. However, the metal itself was obtained only in 1807 by G. Davy by electrolysis of caustic soda NaOH. In the UK, USA, France, the element is called Sodium (from the Spanish word soda - soda), in Italy - sodio.

Spreadingnatria in nature.

Sodium is a typical element in the upper part of the earth's crust. Its average content in the lithosphere is 2.5% by mass, in acidic igneous rocks (granites and others) 2.77, in basic rocks (basalts and others) 1.94, in ultrabasic rocks (mantle rocks) 0.57. Due to the isomorphism of Na + and Ca 2+, due to the proximity of their ionic radii, sodium-calcium feldspars (plagioclases) are formed in igneous rocks. In the biosphere there is a sharp differentiation of Sodium: sedimentary rocks are, on average, depleted in Sodium (0.66% in clays and shales); there is little of it in most soils (average 0.63%). The total number of Sodium minerals is 222. Na is weakly retained on the continents and brought by rivers to the seas and oceans, where its average content is 1.035% (Na is the main metallic element of sea water). During evaporation, sodium salts are deposited in coastal sea lagoons, as well as in continental lakes of steppes and deserts, forming strata of salt-bearing rocks. The main minerals that are the source of Sodium and its compounds are halite (rock salt) NaCl, Chilean saltpeter NaNO 3, thenardite Na 2 SO 4, mirabilite Na 2 SO 4 10H 2 O, trona NaH(CO 3) 2 2H 2 O . Na is an important bioelement; living matter contains on average 0.02% Na; There is more of it in animals than in plants.

Physical propertiesnatrium

At ordinary temperature, Sodium crystallizes in a cubic lattice, a = 4.28 Å. Atomic radius 1.86Å, ionic radius Na+ 0.92Å. Density 0.968 g/cm 3 (19.7 °C), melting point 97.83 °C, boiling point 882.9 °C; specific heat capacity (20 °C) 1.23 10 3 J/(kg K) or 0.295 cal/(g deg); thermal conductivity coefficient 1.32·10 2 W/(m·K) or 0.317 cal/(cm·sec·deg); temperature coefficient of linear expansion (20 °C) 7.1·10 -5; electrical resistivity (0 °C) 4.3·10 -8 ohm·m (4.3·10 -6 ohm·cm). Sodium is paramagnetic, specific magnetic susceptibility +9.2·10 -6; very plastic and soft (easily cut with a knife).

Chemical propertiesnatrium

Normal electrode potential of Sodium is -2.74 V; electrode potential in the melt -2.4 V. Sodium vapor colors the flame a characteristic bright yellow color. The configuration of the outer electrons of the atom is 3s 1; In all known compounds, Sodium is monovalent. Its chemical activity is very high. When directly interacting with oxygen, depending on the conditions, Na 2 O oxide or Na 2 O 2 peroxide is formed - colorless crystalline substances. With water, Sodium forms hydroxide NaOH and H 2; the reaction may be accompanied by an explosion. Mineral acids form corresponding water-soluble salts with Sodium, however, Sodium is relatively inert with respect to 98-100% sulfuric acid.

The reaction of Sodium with hydrogen begins at 200 °C and leads to the production of NaH hydride, a colorless hygroscopic crystalline substance. Sodium reacts directly with fluorine and chlorine even at ordinary temperatures, with bromine - only when heated; no direct interaction is observed with iodine. It reacts violently with sulfur, forming sodium sulfide; the interaction of sodium vapor with nitrogen in the field of a quiet electric discharge leads to the formation of Na 3 N nitride, and with carbon at 800-900 ° C - to the production of Na 2 C 2 carbide.

Sodium dissolves in liquid ammonia (34.6 g per 100 g NH 3 at 0°C) to form ammonia complexes. When gaseous ammonia is passed through molten Sodium at 300-350 °C, sodium amine NaNH 2 is formed - a colorless crystalline substance that is easily decomposed by water. A large number of organosodium compounds are known, which in chemical properties are very similar to organolithium compounds, but are superior to them in reactivity. Organosodium compounds are used in organic synthesis as alkylating agents.

Sodium is a component of many practically important alloys. Na–K alloys, containing 40-90% K (by mass) at a temperature of about 25°C, are silvery-white liquids that are highly chemically reactive and flammable in air. The electrical and thermal conductivities of liquid Na–K alloys are lower than the corresponding values ​​for Na and K. Sodium amalgams are easily obtained by introducing metallic Sodium into mercury; with a content of more than 2.5% Na (by weight) at ordinary temperatures they are already solid substances.

Receiptnatrium.

The main industrial method for producing Sodium is the electrolysis of molten NaCl salt containing additives KCl, NaF, CaCl 2 and others, which reduce the melting point of the salt to 575-585 °C. Electrolysis of pure NaCl would lead to large losses of Sodium from evaporation, since the melting points of NaCl (801 °C) and boiling points of Na (882.9 °C) are very close. Electrolysis is carried out in electrolyzers with a diaphragm, the cathodes are made of iron or copper, the anodes are made of graphite. Chlorine is produced simultaneously with Sodium. The old method of obtaining Sodium is the electrolysis of molten sodium hydroxide NaOH, which is much more expensive than NaCl, but electrolytically decomposes at a lower temperature (320-330 ° C).

Applicationnatrium.

Sodium and its alloys are widely used as coolants for processes requiring uniform heating in the range of 450-650 °C - in aircraft engine valves and especially in nuclear power plants. In the latter case, Na–K alloys serve as liquid metal coolants (both elements have small thermal neutron absorption cross sections, for Na 0.49 barn); these alloys are characterized by high boiling points and heat transfer coefficients and do not interact with structural materials at high temperatures developed in power plants. nuclear reactors. The NaPb compound (10% Na by weight) is used in the production of tetraethyl lead, the most effective anti-knock agent. In the lead-based alloy (0.73% Ca, 0.58% Na and 0.04% Li) used for the manufacture of axle bearings for railway cars, Sodium is a strengthening additive. In metallurgy, Sodium serves as an active reducing agent in the production of some rare metals (Ti, Zr, Ta) by metallothermic methods; in organic synthesis - in reactions of reduction, condensation, polymerization and others.

Due to the high chemical activity of Sodium, handling it requires caution. It is especially dangerous if water comes into contact with Sodium, which can lead to fire and explosion. Eyes should be protected with goggles, hands with thick rubber gloves; Contact of Sodium with wet skin or clothing may cause severe burns.

An inorganic substance, a simple element of the periodic table, belongs to the group of alkali metals. It ranks sixth in abundance in the earth's crust; it is most abundant among metals dissolved in the waters of seas and oceans. It is found in the form of compounds in minerals such as halite, mirabilite, thenardite, sodium nitrate, trona, borax, etc. It is not found in its pure form.

Industrial production method: electrolysis of molten sodium chloride (table salt). Sodium and chlorine are produced at the same time.

Properties

Silver-colored ductile metal. In air it quickly oxidizes and fades. It is so soft that it can be cut with a scalpel, rolled, pressed. Lighter than water. Conducts current and heat well. The color of the flame is bright yellow. This reaction is typical for the detection of many sodium compounds.

It is a chemically very active metal and has basic properties. Reacts with oxygen, carbon dioxide, dilute and concentrated acids, alcohols, gaseous and liquid ammonia, oxides. Self-ignites when interacting with chlorine and fluorine, reacts violently with water (sometimes with an explosion), bromine, and sulfur. Reacts with almost all non-metals (sometimes this requires special conditions, electric discharge or high temperature). With water it forms a strong alkali - sodium hydroxide (caustic soda). Forms compounds with mercury and some other metals, with organic substances.

Sodium has a very significant difference between its melting and boiling points - almost 800 degrees. It melts at about +98 °C, boils at +883 °C. Thanks to this property, sodium makes a good coolant for powerful nuclear reactors, which does not boil to high temperatures.

Sodium plays an important role in the life of living organisms. It is necessary for normal metabolism, the functioning of the nervous and cardiovascular systems. Lack of sodium leads to disturbances in the gastrointestinal tract, convulsions, and neuralgia. Excess - leads to edema, increased blood pressure, problems with kidney function.

Precautionary measures

Sodium should not be handled by hand, as it immediately reacts with skin moisture and forms an alkali, causing severe chemical and thermal burns.

Store sodium under a layer of kerosene or mineral oil in sealed iron containers (the liquid should completely cover the reagent). If stored in a glass container, then it, in turn, must be placed in a fireproof metal cabinet.

After working with sodium metal, residues should be neutralized with alcohol, under no circumstances allowing sodium particles to enter the trash can or drain, as this can cause a fire and rapid destruction of sewer pipes.

Application

Reducing properties are used when obtaining pure metals: potassium, zirconium, tantalum, etc.
In gas discharge lamps.
In metallurgy, sodium is added to lead alloys to give them strength. It makes alloys of other metals more refractory.
In electrical engineering, sodium is used to make energy-intensive batteries, truck engine valves, and tires for very high currents.
Since sodium does not absorb neutrons well, it is used as a coolant in fast neutron nuclear reactors.
For drying organic solvents, for qualitative analysis in organic chemistry.
Sodium isotopes are used in medicine and scientific research.
Many salts are used in the food industry: glutamate, chloride, bicarbonate, benzoate, nitrite, sodium saccharinate.
Table salt is used in water purification.
Sodium hydroxide is in demand in the production of paper, soap, and synthetic fibers; as an electrolyte.
Sodium carbonates and bicarbonates are used in fire fighting and pharmaceuticals.
Sodium phosphate is necessary for the production of detergents, paints, in the glass industry, and photography.
Sodium silicates are used in the production of fire- and acid-resistant concrete.
Azide, cyanide, chlorate, peroxide, tetraborate, sulfate, sodium thiosulfate and many other of its compounds are used.