Na 2 O → NaCl → NaOH → Na.

Na 2 O+ 2HCl → 2NaCl + H 2 O.

To obtain sodium hydroxide from the chloride of the same metal, it is necessary to dissolve it in water, however, it should be remembered that hydrolysis does not occur in this case:

NaCl+ H 2 O → NaOH + HCl.

Obtaining sodium from the corresponding hydroxide is possible if the alkali is subjected to electrolysis:

NaOH ↔ Na + + Cl - ;

K(-): Na + + e → Na 0:

A(+): 4OH — — 4e → 2H 2 O + O 2 .

Atomic mass is the sum of the masses of all protons, neutrons and electrons that make up an atom or molecule. Compared to protons and neutrons, the mass of electrons is very small, so it is not taken into account in calculations. Although this is not formally correct, the term is often used to refer to the average atomic mass of all isotopes of an element. This is actually relative atomic mass, also called atomic weight element. Atomic weight is the average of the atomic masses of all isotopes of an element found in nature. Chemists must differentiate between these two types of atomic mass when doing their work—an incorrect atomic mass value can, for example, result in an incorrect result for the yield of a reaction product.

Steps

Finding atomic mass from the periodic table of elements

Learn how atomic mass is written. Atomic mass, that is, the mass of a given atom or molecule, can be expressed in standard SI units - grams, kilograms, and so on. However, because atomic masses expressed in these units are extremely small, they are often written in unified atomic mass units, or amu for short. – atomic mass units. One atomic mass unit is equal to 1/12 the mass of the standard isotope carbon-12.

• The atomic mass unit characterizes the mass one mole of a given element in grams. This value is very useful in practical calculations, since it can be used to easily convert the mass of a given number of atoms or molecules of a given substance into moles, and vice versa.

1. Find the atomic mass in the periodic table. Most standard periodic tables contain the atomic masses (atomic weights) of each element. As a rule, they are given as a number at the bottom of the cell with the element, under the letters indicating chemical element. Usually this is not a whole number, but a decimal fraction.

   Remember that the periodic table gives the average atomic masses of elements. As noted earlier, the relative atomic masses given for each element in the periodic table are the average of the masses of all isotopes of the atom. This average value is valuable for many practical purposes: for example, it is used in calculating the molar mass of molecules consisting of several atoms. However, when you are dealing with individual atoms, this value is usually not enough.

   • Since the average atomic mass is an average of several isotopes, the value shown in the periodic table is not accurate the value of the atomic mass of any single atom.
   • The atomic masses of individual atoms must be calculated taking into account the exact number of protons and neutrons in a single atom.

   Calculation of the atomic mass of an individual atom

   1. Find the atomic number of a given element or its isotope. Atomic number is the number of protons in the atoms of an element and never changes. For example, all hydrogen atoms, and only they have one proton. The atomic number of sodium is 11 because it has eleven protons in its nucleus, while the atomic number of oxygen is eight because it has eight protons in its nucleus. You can find the atomic number of any element in the periodic table - in almost all its standard versions, this number is indicated above the letter designation of the chemical element. The atomic number is always a positive integer.

      • Suppose we are interested in the carbon atom. Carbon atoms always have six protons, so we know that its atomic number is 6. In addition, we see that in the periodic table, at the top of the cell with carbon (C) is the number "6", indicating that the atomic carbon number is six.
      • Note that the atomic number of an element is not uniquely related to its relative atomic mass in the periodic table. Although, especially for the elements at the top of the table, it may appear that an element's atomic mass is twice its atomic number, it is never calculated by multiplying the atomic number by two.

   2. Find the number of neutrons in the nucleus. The number of neutrons can be different for different atoms of the same element. When two atoms of the same element with the same number of protons have different numbers of neutrons, they are different isotopes of that element. Unlike the number of protons, which never changes, the number of neutrons in the atoms of a given element can often change, so the average atomic mass of an element is written as a decimal fraction with a value lying between two adjacent whole numbers.

      Add up the number of protons and neutrons. This will be the atomic mass of this atom. Ignore the number of electrons that surround the nucleus - their total mass is extremely small, so they have virtually no effect on your calculations.

   Calculating the relative atomic mass (atomic weight) of an element

   1. Determine which isotopes are contained in the sample. Chemists often determine the isotope ratios of a particular sample using a special instrument called a mass spectrometer. However, in training, this data will be provided to you in assignments, tests, and so on in the form of values ​​​​taken from the scientific literature.

      • In our case, let's say that we are dealing with two isotopes: carbon-12 and carbon-13.

   2. Determine the relative abundance of each isotope in the sample. For each element, different isotopes occur in different ratios. These ratios are almost always expressed as percentages. Some isotopes are very common, while others are very rare—sometimes so rare that they are difficult to detect. These values ​​can be determined using mass spectrometry or found in a reference book.

      • Let's assume that the concentration of carbon-12 is 99% and carbon-13 is 1%. Other carbon isotopes really exist, but in quantities so small that in this case they can be neglected.

   3. Multiply the atomic mass of each isotope by its concentration in the sample. Multiply the atomic mass of each isotope by its percentage abundance (expressed as a decimal). To convert percentages to a decimal, simply divide them by 100. The resulting concentrations should always add up to 1.

      • Our sample contains carbon-12 and carbon-13. If carbon-12 makes up 99% of the sample and carbon-13 makes up 1%, then multiply 12 (the atomic mass of carbon-12) by 0.99 and 13 (the atomic mass of carbon-13) by 0.01.
      • The reference books give percentages based on the known quantities of all isotopes of a particular element. Most chemistry textbooks contain this information in a table at the end of the book. For the sample being studied, the relative concentrations of isotopes can also be determined using a mass spectrometer.

   4. Add up the results. Sum up the multiplication results you got in the previous step. As a result of this operation, you will find the relative atomic mass of your element - the average value of the atomic masses of the isotopes of the element in question. When considering an element as a whole, rather than a specific isotope of a given element, this is the value used.

      • In our example, 12 x 0.99 = 11.88 for carbon-12, and 13 x 0.01 = 0.13 for carbon-13. The relative atomic mass in our case is 11.88 + 0.13 = 12,01 .
   • Some isotopes are less stable than others: they break down into atoms of elements with fewer protons and neutrons in the nucleus, releasing particles that make up the atomic nucleus. Such isotopes are called radioactive.

(Natrium, Na) - a chemical element with atomic number 11, and the corresponding simple substance - an alkaline silvery-white soft metal, chemically very active, oxidizes quickly in air.
Density 0.968, melting temperature 97.83 ° C, boiling temperature 882.9 ° C, coefficient. Op. Mohs 0.5. Sodium is a very common lithophile element (sixth place among chemical elements), its Clarke is 2.64 by mass. More than 220 sodium minerals of different classes are known (feldspars, plagioclase, halite, saltpeter, thenardite, mirabilite). The abundance of sodium (in% by mass) in stony meteorites is 7x10 -1, in ultrabasic rocks 5.7 x 10 -1, basic -1.94, in intermediate - 3.0, in acidic - 2.77, in clays - 0 .96, in sandstones – 0.33, in carbonate rocks – 0.04, in ocean water – 1.03534. Sodium is used as a reducing agent, coolant, etc. Sodium salts are widely used in various sectors of the economy.
Story
Sodium was first obtained by the English chemist Humphry Davy in 1807 by electrolysis of solid NaOH.
Distribution in nature
Sodium belongs to the most common elements. It accounts for 2.64% of the mass of the earth's crust. Due to its high chemical activity, it is found only in the form of various compounds. Some of them, such as sodium chloride and sodium sulfate, form powerful deposits.
The largest deposits of sodium chloride NaCl (rock salt, or halite) are in the Urals in the areas of Solikamsk and Sol-Iletsk, in the Donbass and other places. Significant quantities of sodium chloride are extracted in the form of self-salt from the Elton and Baskunchak salt lakes in western Kazakhstan. Huge reserves of sodium sulfate Na 2 SO 4 · 10H 2 O (mirabilite) accumulated in the Kara-Bogaz-Gol Bay in the eastern part of the Caspian Sea.
Physical properties
In its free state, sodium is a silvery-white, light and soft metal. Density – 0.968 g/cm3. Melting point – 97.83 ° C.
Metallic sodium.

Chemical properties
Sodium belongs to the main subgroup of the first group of the Mendeleev periodic system. Its atoms have one electron in their outer electron layer, which they easily lose and turn into ions with one positive charge. Therefore, in its compounds, sodium is only positively monovalent.
Sodium is a very reactive metal. Easily losing its valence electrons, it is a very strong reducing agent. In the electrochemical voltage series, it occupies second place to the left of hydrogen.
In dry air, sodium vigorously interacts with oxygen in the air and turns into peroxide:

2Na + O 2 = Na 2 O 2

Therefore, it is stored under a layer of kerosene or mineral oil. Sodium reacts very vigorously with halogens to form salts of halogenated acids: NaCl, NaBr, etc. It combines with liquid bromine even explosively. When heated with sulfur, it forms sulfides: Na 2 S. It reacts very violently with water, even explosively. Reacts even more violently with acids (also explosively). In humid air, the metal easily turns into hydroxide:

2Na + 2H2O = 2NaOH + H2?

And the latter, interacting with carbon dioxide air, – into carbonate:

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

At high temperatures, sodium can reduce oxides of aluminum, silicon, etc. to free elements:

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

Receipt
In the free state, sodium is obtained by electrolysis of molten chlorides or hydroxides. During the electrolysis of molten caustic alkalis, positively charged metal ions are attracted to the negatively charged cathode, add one electron each (reduced) and turn into atoms of free metals, and negatively charged hydroxyl ions are attracted to the positively charged anode, give it one electron each and turn into electrons. neutral OH groups that decompose to form water and oxygen released at the anode. The production of sodium metal by electrolysis of NaOH can be represented by the following equations:
NaOH? ? – Cathode Anode + 4Na + + 4e = 4Na ° 4OH - – 4e = 4OH ° 4OH ° = 2H 2 O + O 2 ?
Application
Metallic sodium is used in the synthesis of many organic substances, for the manufacture of some alloys, as well as in metallurgy for the production of a number of metals from their compounds, for example titanium by the reaction

TiCl 4 + 4Na = Ti + 4NaCl

Sodium salts
Sodium forms salts with all acids. The vast majority of sodium salts dissolve well in water. The most important of them:

Sodium chloride NaCl, or table salt
Sodium carbonate Na 2 CO 3, or soda
Sodium bicarbonate NaHCO 3, or baking soda
Sodium sulfate Na 2 SO 4

The most interesting topic in school chemistry lessons was the properties of active metals. We were not only given theoretical material, but also interesting experiments were demonstrated. Probably everyone remembers how the teacher threw a small piece of metal into the water, and it rushed along the surface of the liquid and ignited. In this article we will understand how the reaction of sodium and water occurs and why metal explodes.

Sodium metal is a silvery substance, similar in density to soap or paraffin. Sodium is characterized by good thermal and electrical conductivity. That is why it is used in industry, in particular for the manufacture of batteries.

Sodium is highly chemically reactive. Often reactions occur with the release of large amounts of heat. Sometimes this is accompanied by fire or explosion. Working with active metals requires good information training and experience. Sodium can only be stored in well-closed containers under a layer of oil, since the metal quickly oxidizes in air.

The most popular reaction of sodium is its interaction with water. The reaction of sodium plus water produces an alkali and hydrogen:

2Na + 2H2O = 2NaOH + H2

Hydrogen is oxidized by oxygen from the air and explodes, which is what we observed during the school experiment.

Reaction studies by scientists from the Czech Republic

The reaction of sodium with water is very simple to understand: the interaction of the substances leads to the formation of H2 gas, which in turn is oxidized by O2 in the air and ignites. It seems simple. But Professor Pavel Jungvirt from the Czech Academy of Sciences did not think so.

The fact is that during the reaction not only hydrogen is formed, but also water vapor, since large number energy, the water heats up and evaporates. Since sodium has a low density, the vapor cushion must push it upward, isolating it from the water. The reaction should die down, but it doesn't.

Jungwirth decided to study this process in detail and filmed the experiment with a high-speed camera. The process was filmed at 10 thousand frames per second and viewed at 400x slow motion. Scientists noticed that metal, entering the liquid, begins to produce processes in the form of spikes. This is explained as follows:

• Alkali metals, once in water, begin to act as electron donors and give off negatively charged particles.
• A piece of metal acquires a positive charge.
• The positively charged protons begin to repel each other, forming metallic appendages.
• The spikes pierce the steam cushion, the contact surface of the reacting substances increases, and the reaction intensifies.

How to conduct an experiment

In addition to hydrogen, alkali is formed during the reaction of water and sodium. To check this, you can use any indicator: litmus, phenolphthalein or methyl orange. It will be easiest to work with phenolphthalein, since it is colorless in a neutral environment and the reaction will be easier to observe.

To conduct the experiment you need:

1. Pour distilled water into the crystallizer so that it occupies more than half the volume of the vessel.
2. Add a few drops of indicator to the liquid.
3. Cut a piece of sodium the size of half a pea. To do this, use a scalpel or a thin knife. You need to cut metal in a container, without removing the sodium from the oil, to avoid oxidation.
4. Remove the piece of sodium from the jar with tweezers and blot with filter paper to remove any oil.
5. Throw sodium into the water and observe the process from a safe distance.

All instruments used in the experiment must be clean and dry.

You will see that sodium does not sink into the water, but remains on the surface, due to the density of the substances. The sodium will begin to react with the water, releasing heat. This will cause the metal to melt and turn into a droplet. This droplet will begin to actively move through the water, emitting a characteristic hissing sound. If the sodium piece was not too small, it will light up with a yellow flame. If the piece was too large, an explosion may occur.

The water will also change color. This is explained by the release of alkali into the water and the coloring of the indicator dissolved in it. Phenolphthalein will turn pink, litmus blue, and methyl orange yellow.

It's dangerous

The interaction of sodium with water is very dangerous. Serious injury may occur during the experiment. The hydroxide, peroxide and sodium oxide that are formed during the reaction can corrode the skin. Alkali splashing can get into your eyes and cause serious burns and even blindness.

The name "sodium" comes from the Latin word sodium(cf. ancient Greek νίτρον), which was borrowed from the Middle Egyptian language ( nṯr), where it meant, among other things: “soda”, “caustic soda”.

Abbreviation "Na" and the word sodium were first used by academician, founder of the Swedish Society of Physicians, Jöns Jakob Berzelius (1779-1848) to refer to natural mineral salts, which included soda. Previously (and also still in English, French and a number of other languages) the element was called sodium(lat. sodium) is the name sodium possibly goes back to the Arabic word suda, meaning “headache,” since soda was used at that time as a cure for headaches.

Sodium was first obtained by the English chemist Humphry Davy, who reported it on November 19, 1807. Baker's lecture(in his lecture manuscript, Davy indicated that he discovered potassium on October 6, 1807, and sodium a few days after potassium), by electrolysis of molten sodium hydroxide.

Being in nature

Instead of coal, calcium carbide, aluminum, silicon, ferrosilicon, and silicoaluminum can be used.

With the advent of electric power, another method of producing sodium became more practical - electrolysis of molten caustic soda or sodium chloride. Currently, electrolysis is the main method for producing sodium.

Sodium can also be obtained by the zirconium thermal method or by thermal decomposition of sodium azide.

Physical properties

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 electrical and thermal conductivity values ​​of sodium are quite high, the density is 0.96842 g/cm³ (at 19.7 °C), the melting point is 97.86 °C, and the boiling point is 883.15 °C.

Under pressure it becomes transparent and red, like a ruby.

At room temperature, sodium forms crystals in the cubic system, space group I m 3m, cell parameters a= 0.42820 nm, Z = 2 .

At a temperature of −268 °C (5 K), sodium transforms into the hexagonal phase, space group P 6 3 /mmc, cell parameters a= 0.3767 nm, c= 0.6154 nm, Z = 2 .

Chemical properties

Alkali metal in air easily oxidizes to sodium oxide. To protect against atmospheric oxygen, sodium metal is stored under a layer of kerosene.

When burned in air or oxygen, sodium peroxide is formed:

Sodium reacts very violently with water; a piece of sodium placed in water floats up, melts due to the heat generated, turning into a white ball that quickly moves in different directions on the surface of the water, the reaction occurs with the release of hydrogen, which can ignite. Reaction equation:

Like all alkali metals, sodium is a strong reducing agent and reacts vigorously with many non-metals (with the exception of nitrogen, iodine, carbon, noble gases):

Sodium is also used in high- and high-gas discharge lamps. low pressure(NLVD and NLND). NLVD lamps of the DNaT (Arc Sodium Tubular) type are very widely used in street lighting. They give off a bright yellow light. The service life of HPS lamps is 12-24 thousand hours. Therefore, gas-discharge lamps of the HPS type are indispensable for urban, architectural and industrial lighting. There are also lamps DNaS, DNaMT (Arc Sodium Matte), DNaZ (Arc Sodium Mirror) and DNaTBR (Arc Sodium Tubular Without Mercury).

Sodium metal is used in the qualitative analysis of organic matter. The alloy of sodium and the test substance is neutralized with ethanol, a few milliliters of distilled water are added and divided into 3 parts; the J. Lassaigne test (1843) is aimed at determining nitrogen, sulfur and halogens (Beilstein test).

Sodium chloride (table salt) is the oldest used flavoring and preservative.

Sodium azide (NaN 3) is used as a nitriding agent in metallurgy and in the production

Sodium —element the main subgroup of the first group, the third period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 11. Denoted by the symbol Na (lat. Natrium). The simple substance sodium (CAS number: 7440-23-5) is a soft alkali metal with a silvery-white color.

In water, sodium behaves almost the same as lithium: the reaction proceeds with the rapid release of hydrogen, and sodium hydroxide is formed in the solution.

History and origin of the name

Sodium (or rather, its compounds) has been used since ancient times. For example, soda (natron), found naturally in the waters of soda lakes in Egypt. The ancient Egyptians used natural soda for embalming, bleaching canvas, cooking food, and making paints and glazes. Pliny the Elder writes that in the Nile Delta, soda (it contained a sufficient proportion of impurities) was isolated from river water. It went on sale in the form of large pieces, colored gray or even black due to the admixture of coal.

Sodium was first obtained by the English chemist Humphry Davy in 1807 by electrolysis of solid NaOH.

The name "sodium" comes from the Arabic natrun in Greek - nitron and originally it referred to natural soda. The element itself was previously called Sodium.

Receipt

The first way to produce sodium was the reduction reaction sodium carbonate coal when heating a close mixture of these substances in an iron container to 1000°C:

Na 2 CO 3 +2C=2Na+3CO

Then another method of producing sodium appeared - electrolysis of molten sodium hydroxide or sodium chloride.

Physical properties

Metallic sodium stored in kerosene

Qualitative determination of sodium using a flame - bright yellow color of the emission spectrum of the “sodium D-line”, doublet 588.9950 and 589.5924 nm.

Sodium is a silvery-white metal, in thin layers with a violet tint, plastic, even soft (easily cut with a knife), a fresh cut of sodium is shiny. The electrical and thermal conductivity values ​​of sodium are quite high, the density is 0.96842 g/cm³ (at 19.7° C), the melting point is 97.86° C, and the boiling point is 883.15° C.

Chemical properties

An alkali metal that oxidizes easily in air. To protect against atmospheric oxygen, metallic sodium is stored under a layer kerosene. Sodium is less active than lithium, therefore with nitrogen reacts only when heated:

2Na + 3N 2 = 2NaN 3

When there is a large excess of oxygen, sodium peroxide is formed

2Na + O 2 = Na 2 O 2

Application

Sodium metal is widely used in preparative chemistry and industry as a strong reducing agent, including in metallurgy. Sodium is used in the production of highly energy-intensive sodium-sulfur batteries. It is also used in truck exhaust valves as a heat sink. Occasionally, sodium metal is used as a material for electrical wires, designed for very high currents.

In an alloy with potassium, as well as with rubidium and cesium used as a highly efficient coolant. In particular, the alloy composition is sodium 12%, potassium 47 %, cesium 41% have a record low temperature melting point −78 °C and was proposed as a working fluid for ion rocket engines and coolant for nuclear power plants.

Sodium is also used in high and low pressure discharge lamps (HPLD and LPLD). NLVD lamps of the DNaT (Arc Sodium Tubular) type are very widely used in street lighting. They give off a bright yellow light. The service life of HPS lamps is 12-24 thousand hours. Therefore, gas-discharge lamps of the HPS type are indispensable for urban, architectural and industrial lighting. There are also lamps DNaS, DNaMT (Arc Sodium Matte), DNaZ (Arc Sodium Mirror) and DNaTBR (Arc Sodium Tubular Without Mercury).

Sodium metal is used in the qualitative analysis of organic matter. The alloy of sodium and the test substance is neutralized ethanol, add a few milliliters of distilled water and divide into 3 parts, J. Lassaigne's test (1843), aimed at determining nitrogen, sulfur and halogens (Beilstein test)

— Sodium chloride (table salt) is the oldest used flavoring and preservative.
— Sodium azide (Na 3 N) is used as a nitriding agent in metallurgy and in the production of lead azide.
— Sodium cyanide (NaCN) is used in the hydrometallurgical method of leaching gold from rocks, as well as in the nitrocarburization of steel and in electroplating (silvering, gilding).
— Sodium chlorate (NaClO 3) is used to destroy unwanted vegetation on railway tracks.

Biological role

In the body, sodium is found mostly outside the cells (about 15 times more than in the cytoplasm). This difference is maintained by the sodium-potassium pump, which pumps out sodium trapped inside the cell.

Together withpotassiumsodium performs the following functions:
Creating conditions for the occurrence of membrane potential and muscle contractions.
Maintaining blood osmotic concentration.
Maintaining acid-base balance.
Normalization of water balance.
Ensuring membrane transport.
Activation of many enzymes.

Sodium is found in almost all foods, although the body gets most of it from table salt. Absorption mainly occurs in the stomach and small intestine. Vitamin D improves the absorption of sodium, however, excessively salty foods and foods rich in protein interfere with normal absorption. The amount of sodium taken in from food shows the sodium content in the urine. Sodium-rich foods are characterized by accelerated excretion.

Sodium deficiency in the dieter balanced food does not occur in humans, however, some problems can arise with vegetarian diets. Temporary deficiency may be caused by diuretic use, diarrhea, excessive sweating, or excess water intake. Symptoms of sodium deficiency include weight loss, vomiting, gas in the gastrointestinal tract, and impaired absorption amino acids and monosaccharides. Long-term deficiency causes muscle cramps and neuralgia.

Excess sodium causes swelling of the legs and face, as well as increased excretion of potassium in the urine. Maximum quantity salt that can be processed by the kidneys is approximately 20-30 grams; a larger amount is already life-threatening.

Sodium compounds

Sodium, Natrium, Na (11)
The name sodium - sodium, natrium comes from an ancient word common in Egypt, among the ancient Greeks (vixpov) and Romans. It is found in Pliny (Nitron) and other ancient authors and corresponds to the Hebrew neter. In ancient Egypt, natron, or nitron, was generally called an alkali obtained not only from natural soda lakes, but also from plant ash. It was used for washing, making glazes, and mummifying corpses. In the Middle Ages, the name nitron (nitron, natron, nataron), as well as boron (baurach), also applied to saltpeter (Nitrum). Arab alchemists called alkali alkali. With the discovery of gunpowder in Europe, saltpeter (Sal Petrae) began to be strictly distinguished from alkalis, and in the 17th century. already distinguished between non-volatile, or fixed alkalis, and volatile alkali (Alkali volatile). At the same time, a difference was established between vegetable (Alkali fixum vegetabile - potash) and mineral alkali (Alkali fixum minerale - soda).

At the end of the 18th century. Klaproth introduced the name Natron, or soda, for the mineral alkali, and for the vegetable alkali, Kali. Lavoisier did not place alkali in the “Table of Simple Bodies,” indicating in a note to it that these were probably complex substances that once Someday they will be decomposed. Indeed, in 1807 Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. The following year, Gilbert, publisher of the famous Annals of Physics, proposed calling the new metals potassium and sodium (Natronium); Berzelius shortened the latter name to “sodium” (Natrium). At the beginning of the 19th century. in Russia sodium was called sodia (Dvigubsky, 182i; Solovyov, 1824); Strakhov proposed the name sod (1825). Sodium salts were called, for example, soda sulfate, hydrochloric soda, and at the same time acetic soda (Dvigubsky, 1828). Hess, following the example of Berzelius, introduced the name 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 information. 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.

Distribution of Sodium 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%). Total number minerals Sodium 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 properties of Sodium. 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; specific electrical resistance(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 properties of Sodium. 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 chemical properties are very similar to organolithium compounds, but surpass 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, characterized by high chemical activity, flammable in air. The electrical conductivity and thermal conductivity 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.

Obtaining Sodium. 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 electrolytic cells with a diaphragm, the cathodes are made of iron or copper, and the anodes are made of graphite. Chlorine is produced simultaneously with Sodium. The old way obtaining Sodium - electrolysis of molten sodium hydroxide NaOH, which is much more expensive than NaCl, but electrolytically decomposes at a lower temperature (320-330 ° C).

Application of Sodium. 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 in 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.

Sodium in the body. Sodium is one of the main elements involved in the mineral metabolism of animals and humans. Contained mainly in extracellular fluids (about 10 mmol/kg in human erythrocytes, 143 mmol/kg in blood serum); participates in maintaining osmotic pressure and acid-base balance, in the conduction of nerve impulses. A person's daily need for sodium chloride ranges from 2 to 10 g and depends on the amount of this salt lost through sweat. The concentration of sodium ions in the body is regulated mainly by the hormone of the adrenal cortex - aldosterone. The sodium content in plant tissues is relatively high (about 0.01% by wet weight). In halophytes (species growing on highly saline soils), sodium creates high osmotic pressure in the cell sap and thereby promotes the extraction of water from the soil.

In medicine, the most commonly used sodium preparations are sodium sulfate, NaCl chloride (for blood loss, fluid loss, vomiting, etc.), Na 2 B 4 O 7 10H 2 O borate (as an antiseptic), NaHCO 3 bicarbonate (as expectorant, as well as for washing and rinsing for rhinitis, laryngitis and others), Na 2 S 2 O 3 5H 2 O thiosulfate (anti-inflammatory, desensitizing and antitoxic agent) and Na 3 C 6 H 5 O 7 5½H 2 O citrate (a drug from the group of anticoagulants).

Artificially obtained radioactive isotopes 22 Na (half-life T ½ = 2.64 g) and 24 Na (T ½ = 15 hours) are used to determine the speed of blood flow in individual areas circulatory system for cardiovascular and pulmonary diseases, obliterating endarteritis and others. Radioactive solutions of Sodium salts (for example, 24 NaCl) are also used to determine vascular permeability, study the total content of exchangeable Sodium in the body, water-salt metabolism, absorption from the intestines, processes of nervous activity, and in some other experimental studies.

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