Sodium(Natrium), Na, chemical element of group I periodic table 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%). 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 metal element 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(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 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 - colorless crystalline substance, easily decomposed by water. Known large number organosodium compounds, which have chemical properties 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, 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 electrolyzers 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 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).
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 energy 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 certain parts of the circulatory system in 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.
Sodium is a simple substance located in the first group of the third period of the periodic table of chemical elements by D.I. Mendeleev. It is a very soft, silvery alkali metal that has a violet hue when divided into thin layers. The melting point of sodium is just below that required for water to boil, and the boiling point is 883 degrees Celsius. At room temperature its density is 0.968 g/cm3. Due to its low density, sodium can be cut with a regular knife if necessary.
Sodium is very common on our planet: its various compounds can be found here both in the sea or the earth’s crust, where it is found in relatively large quantities, and in many living organisms, but is not found in living nature in pure form due to its amazingly high activity. Sodium is one of the essential microelements necessary for normal human life - therefore, to replenish its natural loss from the body, it is necessary to consume about 4-5 grams of its compound with chlorine - i.e. regular table salt.
Sodium in history
Various sodium compounds have been known to man since the time ancient egypt. The Egyptians were the first to actively use sodium-containing soda from the salty Lake Natron for various everyday needs. Sodium compounds were even mentioned in the Bible as a component detergent However, sodium was first obtained in its pure form by the English chemist Humphrey Devy in 1807, during experiments with its derivative substances.
Initially, sodium was called sodium - a derivative of Arabic word, indicating headache. The word "sodium" was borrowed from the Egyptian language and for the first time, in modern history, was used by the Swedish Society of Physicians as a designation for soda-containing mineral salts.
Chemical properties of sodium
Sodium is an active alkali metal – i.e. It oxidizes very quickly upon contact with air and must be stored in kerosene, while sodium has a very low density and often floats to its surface. Being a very strong reducing agent, sodium reacts with most non-metals, and being an active metal, reactions with its use often occur very quickly and violently. For example, if you place a piece of sodium in water, it begins to actively ignite, which ultimately leads to an explosion. Ignition and the release of oxygen occur when sodium and its derivatives react with many other substances, but with dilute acids it reacts like an ordinary metal. Sodium does not react with noble gases, iodine and carbon, and also reacts very poorly with nitrogen, forming a rather unstable substance in the form of dark gray crystals - sodium nitride.
Applications of sodium
Sodium is mainly used in the chemical industry and metallurgy, where, most often, it is used as a reducing agent, due to its chemical properties. It is also used as a desiccant for such organic solvents like ether and others like it; for the production of wires capable of withstanding enormous voltages. In the same area, sodium is used as the main component in the production of sodium-sulfur batteries, which have a high specific energy, i.e. less fuel consumption. The main disadvantage of this type of battery is the high operating temperature, and, consequently, the risk of ignition and explosion of sodium in an accident.
Another area of application of sodium is pharmacology, where many sodium derivatives are used as reagents, intermediates and excipients in the creation of various complex drugs, as well as antiseptics. A solution of sodium chloride is relatively similar to human blood plasma and is quickly eliminated from the body, so it is used when it is necessary to maintain and normalize blood pressure.
Today, some sodium compounds are an essential component in the production of concrete and other building materials. Thanks to the use of materials containing sodium-derived components, they can be used in construction work during low temperatures.
Due to its abundance and ease of industrial production, sodium has a fairly low cost. Today it is produced in the same way as when it was first obtained - by exposing various sodium-containing rocks to a strong electric current. Thanks to this, as well as its necessity in many types of industry, its production volumes are only growing.
-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 of 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 atom diagram
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
Metallic sodium 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 intended to carry 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% has a record low melting point of −78 °C and has been proposed as a working fluid for ion rocket engines and a 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 qualitative analysis 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
Sodium is found in the body 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 may arise when 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, and gas. gastrointestinal tract, and disruption of 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.
DEFINITION
Sodium- the eleventh element of the Periodic Table. Designation - Na from the Latin "natrium". Located in the third period, group IA. Refers to metals. The nuclear charge is 11.
Sodium is one of the most abundant elements on Earth. It was found in the solar atmosphere and in interstellar space. The most important minerals of sodium: NaCl (halite), Na 2 SO 4 ×10H 2) (mirabelite), Na 3 AlF 6 (cryolite), Na 2 B 4 O 7 ×10H 2) (borax), etc. The content of sodium salts in hydrosphere (about 1.5×10 16 t).
Sodium compounds enter plant and animal organisms, in the latter case, mainly in the form of NaCl. In human blood, Na + ions account for 0.32%, in bones - 0.6%, in muscle tissue - 0.6-1.5%.
In its simple form, sodium is a silvery-white metal (Fig. 1). It is so soft that it can be easily cut with a knife. Due to its easy oxidation in air, sodium is stored under a layer of kerosene.
Rice. 1. Sodium. Appearance.
Atomic and molecular weight of sodium
DEFINITION
Relative molecular mass of the substance (Mr) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms chemical element more than 1/12 the mass of a carbon atom.
Since in the free state sodium exists in the form of monatomic Na molecules, the values of its atomic and molecular masses coincide. They are equal to 22.9898.
Sodium isotopes
Twenty isotopes of sodium are known with mass numbers from 18 to 37, of which the most stable is 23 Na with a half-life of less than a minute.
Sodium ions
The outer energy level of the sodium atom has one electron, which is a valence electron:
1s 2 2s 2 2p 6 3s 1 .
As a result of chemical interaction, sodium gives up its only valence electron, i.e. is its donor, and turns into a positively charged ion:
Na 0 -1e → Na + .
Sodium molecule and atom
In the free state, sodium exists in the form of monoatomic Na molecules. Here are some properties characterizing the sodium atom and molecule:
Sodium alloys
The most important areas of application of sodium are nuclear energy, metallurgy, and the organic synthesis industry. In nuclear energy, sodium and its alloy with potassium are used as liquid metal coolants. An alloy of sodium with potassium, containing 77.2% (wt.) cadium, is in a liquid state in a wide temperature range, has a high heat transfer coefficient and does not interact with most structural materials either at normal or at elevated temperatures.
Sodium is used as an additive to strengthen lead alloys.
With mercury, sodium forms a hard alloy - sodium amalgam, which is sometimes used as a softer reducing agent instead of pure metal.
Examples of problem solving
EXAMPLE 1
| Exercise | Write the reaction equations that can be used to carry out the following transformations: Na 2 O → NaCl → NaOH → Na. |
| Answer | To obtain chloride of the same metal from sodium oxide, it is necessary to dissolve it in acid: 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 . Natron was originally called sodium hydroxide. In 1807, Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. Berzelius and then Hess in Russia proposed the name Natrium, which stuck. Being in nature, receiving:Alkali metals are not found in free form in nature. Sodium is part of various compounds. The most important is the compound of sodium with chlorine NaCl, which forms rock salt deposits (Donbass, Solikamsk, Sol-Iletsk, etc.). Sodium chloride is also found in sea water and salt springs. Sodium is one of the common elements. The sodium content in the earth's crust is 2.64%. Physical properties:Sodium is a silvery-white metal, its density is 0.97 g/cm3, very soft, easy to cut with a knife. There is a metallic bond between atoms. A substance with such a bond is characterized by metallic luster, ductility, softness, good electrical conductivity and thermal conductivity. Chemical properties:During a chemical interaction, a sodium atom easily gives up valence electrons, becoming a positively charged ion. It oxidizes quickly in air, so it is stored under a layer of kerosene. The most important connections:Sodium oxide, Na 2 O (colorless), reacts with water vapor and carbon dioxide, so it is better to store it in anhydrous benzene. Application:Sodium compounds are the most important components of chemical production. Used in soap making, glass production, and household chemicals. Bondareva Maria Alexandrovna Sources: G.P. Khomchenko "A manual on chemistry for those entering universities" |