The most important natural compound of potassium is. Getting potassium: methods, reactions, formulas, types of potassium and its chemical properties. The electronic structure of the potassium atom

- an element of the main subgroup of the first group, the fourth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 19. It is designated by the symbol K (Latin Kalium). Simple substance potassium (CAS number: 7440-09-7) is a soft alkali metal silvery white... In nature, potassium is found only in compounds with other elements, for example, in seawater, as well as in many minerals. It oxidizes very quickly in air and very easily enters into chemical reactions, especially with water, forming an alkali. In many ways, the chemical properties of potassium are very close to sodium, but in terms of biological function and their use by the cells of living organisms, they are still different. History and origin of the name potassium

Potassium (more precisely, its compounds) has been used since ancient times. So, the production of potash (which was used as a detergent) already existed in the 11th century. The ash formed during the combustion of straw or wood was treated with water, and the resulting solution (lye) was evaporated after filtration. The dry residue, in addition to potassium carbonate, contained potassium sulfate K 2 SO 4, soda and potassium chloride KCl.

In 1807, the English chemist Davy isolated potassium by electrolysis of solid caustic potassium (KOH) and named it "Potassius"(lat. potassium; this name is still used in English, French, Spanish, Portuguese and Polish). In 1809 L. V. Gilbert proposed the name "potassium" (lat. kalium, from arab. al-kali - potash). This name entered the German language, from there into most languages ​​of Northern and Eastern Europe (including Russian) and "won" when choosing a symbol for this element - K.

The presence of potassium in nature

Does not occur in a free state. Potassium is a part of sylvinite KCl NaCl, carnallite KCl MgCl 2 6H 2 O, kainite KCl MgSO 4 6H 2 O, and is also present in the ash of some plants in the form of carbonate K 2 CO 3 (potash). Potassium is part of all cells (see section below Biological role).

Potassium - getting potassium

Potassium, like other alkali metals, is produced by electrolysis of molten chlorides or alkalis. Since chlorides have a higher melting point (600-650 ° C), electrolysis of straightened alkalis with the addition of soda or potash (up to 12%) is more often carried out. During the electrolysis of molten chlorides, molten potassium is released at the cathode, and chlorine at the anode:
K + + e - → K
2Cl - - 2e - → Cl 2

During the electrolysis of alkalis, molten potassium is also released at the cathode, and oxygen at the anode:
4OH - - 4e - → 2H 2 O + O 2

The water from the melt evaporates quickly. To prevent potassium from interacting with chlorine or oxygen, the cathode is made of copper and a copper cylinder is placed above it. The resulting potassium in molten form is collected in a cylinder. The anode is also made in the form of a cylinder of nickel (for the electrolysis of alkalis) or of graphite (for the electrolysis of chlorides).

Physical properties of potassium

Potassium is a silvery substance with a characteristic luster on a freshly formed surface. It is very light and easy to melt. It dissolves relatively well in mercury, forming amalgams. When added to the burner flame, potassium (as well as its compounds) colors the flame in a characteristic pink-violet color.

Chemical properties of potassium

Potassium, like other alkali metals, exhibits typical metallic properties and is very reactive, easily donating electrons.

It is a powerful reducing agent. It combines so actively with oxygen that not an oxide is formed, but potassium superoxide KO 2 (or K 2 O 4). When heated in a hydrogen atmosphere, potassium hydride KH is formed. It interacts well with all non-metals, forming halides, sulfides, nitrides, phosphides, etc., as well as with complex substances such as water (the reaction proceeds with an explosion), various oxides and salts. In this case, they reduce other metals to a free state.

Potassium is stored under a layer of kerosene.

Potassium oxides and potassium peroxides

When potassium interacts with atmospheric oxygen, not an oxide is formed, but peroxide and superoxide:

Potassium oxide can be obtained by heating the metal to a temperature not exceeding 180 ° C in an environment containing very little oxygen, or by heating a mixture of potassium superoxide with metallic potassium:

Potassium oxides have pronounced basic properties, react violently with water, acids and acid oxides... They have no practical meaning. Peroxides are yellowish-white powders that dissolve well in water and form alkalis and hydrogen peroxide:

The property of exchanging carbon dioxide for oxygen is used in insulating gas masks and on submarines. An equimolar mixture of potassium superoxide and sodium peroxide is used as an absorber. If the mixture is not equimolar, then in the case of an excess of sodium peroxide, more gas will be absorbed than released (when two volumes of CO 2 are absorbed, one volume of O 2 is released), and the pressure in confined space drops, and in the case of an excess of potassium superoxide (when two volumes of CO 2 are absorbed, three volumes of O 2 are released) more gas is released than is absorbed, and the pressure will rise.

In the case of an equimolar mixture (Na 2 O 2: K 2 O 4 = 1: 1), the volumes of absorbed and emitted gases will be equal (when four volumes of CO 2 are absorbed, four volumes of O 2 are released).

Peroxides are strong oxidants, so they are used for bleaching fabrics in the textile industry.

Peroxides are obtained by calcining metals in air freed from carbon dioxide.

Potassium hydroxides

Potassium hydroxide (or caustic potassium) are solid white, opaque, highly hygroscopic crystals that melt at 360 ° C. Potassium hydroxide is an alkali. It dissolves well in water, giving off a lot of heat. The solubility of caustic potassium at 20 ° C in 100 g of water is 112 g.

Potassium use

• An alloy of potassium and sodium, liquid at room temperature, is used as a coolant in closed systems, for example, in nuclear power plants using fast neutrons. In addition, its liquid alloys with rubidium and cesium are widely used. An alloy with a composition of sodium 12%, potassium 47%, cesium 41% has a record low melting point of −78 ° C.
• Potassium compounds are the most important biogenic element and therefore are used as fertilizers.
• Potassium salts are widely used in electroplating, since, despite their relatively high cost, they are often more soluble than the corresponding sodium salts, and therefore provide intensive work of electrolytes at an increased current density.

Important connections

Purple color of the flame of potassium ions in the flame of the burner

• Potassium bromide - used in medicine and as a sedative for the nervous system.
• Potassium hydroxide (caustic potassium) - used in alkaline batteries and for drying gases.
• Potassium carbonate (potash) - used as a fertilizer in glass melting.
• Potassium chloride (sylvin, "potassium salt") - used as fertilizer.
• Potassium nitrate (potassium nitrate) is a fertilizer, a component of black powder.
• Potassium perchlorate and chlorate (berthollet's salt) are used in the production of matches, rocket powder, lighting charges, explosives, and electroplating.
• Potassium dichromate (chrompik) is a strong oxidizing agent, used to prepare a "chromium mixture" for washing chemical dishes and leather processing (tanning). It is also used for the purification of acetylene in acetylene plants from ammonia, hydrogen sulfide and phosphine.
• Potassium permanganate is a strong oxidizing agent used as an antiseptic in medicine and for the production of oxygen in the laboratory.
• Sodium potassium tartrate (Rochelle salt) as a piezoelectric.
• Potassium dihydrogen phosphate and dideuterophosphate in the form of single crystals in laser technology.
• Potassium peroxide and potassium superoxide are used for air regeneration in submarines and in insulating gas masks (absorbs carbon dioxide with the release of oxygen).
• Potassium fluoroborate is an important flux for brazing steels and non-ferrous metals.
• Potassium cyanide is used in electroplating (silvering, gilding), in gold mining and in steel nitrocarburizing.
• Potassium together with potassium peroxide is used in the thermochemical decomposition of water into hydrogen and oxygen (potassium cycle "Gaz de France", France).

Biological role

Potassium is an essential nutrient, especially in the plant kingdom. With a lack of potassium in the soil, plants develop very poorly, the yield decreases, so about 90% of the extracted potassium salts are used as fertilizers.

Potassium in the human body

Potassium is found mostly in cells, up to 40 times more than in the intercellular space. During the functioning of cells, excess potassium leaves the cytoplasm, therefore, to maintain concentration, it must be pumped back using a sodium-potassium pump.

Potassium and sodium are functionally related to each other and perform the following functions:

• Creation of conditions for the emergence of membrane potential and muscle contractions.
• Maintaining the osmotic concentration of the blood.
• Maintaining acid-base balance.
• Water balance normalization.
• Providing membrane transport.
• Activation of various enzymes.
• Normalization of the heart rhythm.

The recommended daily potassium content for children is from 600 to 1700 milligrams, for adults from 1800 to 5000 milligrams. The need for potassium depends on total weight body, physical activity, physiological condition, and the climate of the place of residence. Vomiting, prolonged diarrhea, profuse sweating, and the use of diuretics increase the body's need for potassium.

The main food sources are dried apricots, melon, beans, kiwi, potatoes, avocados, bananas, broccoli, liver, milk, nut butter, citrus fruits, and grapes. There is a lot of potassium in fish and dairy products.

Absorption takes place in the small intestine. The assimilation of potassium is facilitated by vitamin B6, and it is difficult by alcohol.

With a lack of potassium, hypokalemia develops. Disorders of the heart and skeletal muscles occur. Prolonged potassium deficiency can cause acute neuralgia.

Potassium

POTASSIUM-I am; m.[Arab. kali] Chemical element (K), a silvery-white metal extracted from carbonate salt (potash).

◁ Potassium, th, th. K-th deposits. K-th salts. Potash, th, th. K-th industry. K-th fertilizers.

(lat. Kalium), a chemical element of group I of the periodic system, refers to alkali metals. The name from the Arabic al-kali is potash (a long-known potassium compound extracted from wood ash). Silver-white metal, soft, fusible; density 0.8629 g / cm 3, t pl 63.51ºC. It quickly oxidizes in air, reacts with water explosively. In terms of prevalence in the earth's crust, it takes 7th place (minerals: sylvin, cainite, carnallite, etc.; see Potassium salts). It is part of the tissues of plant and animal organisms. About 90% of the extracted salts are used as fertilizers. Metallic potassium is used in chemical current sources, as a getter in electronic tubes, to obtain superperoxide KO 2; alloys K with Na - coolants in nuclear reactors.

POTASSIUM (lat. Kalium), K (read "potassium"), a chemical element with atomic number 19, atomic mass 39.0983.
Potassium occurs naturally as two stable nuclides (cm. NUCLID): 39 K (93.10% by mass) and 41 K (6.88%), as well as one radioactive 40 K (0.02%). The half-life of potassium-40 T 1/2 is about 3 times less than T 1/2 of uranium-238 and is 1.28 billion years. In the b-decay of potassium-40, stable calcium-40 is formed, and in the decay by the type of electron capture (cm. ELECTRONIC CAPTURE) an inert gas argon-40 is formed.
Potassium is an alkali metal (cm. ALKALINE METALS)... In the periodic system of Mendeleev, potassium occupies a place in the fourth period in the subgroup IA. Configuration of the outer electron layer 4 s 1, therefore potassium always exhibits an oxidation state of +1 (valence I).
The atomic radius of potassium is 0.227 nm, the radius of the K + ion is 0.133 nm. The energies of successive ionization of the potassium atom are 4.34 and 31.8 eV. Electronegativity (cm. ELECTRIC NEGATIVITY) potassium according to Pauling 0.82, which indicates its pronounced metallic properties.
Free - soft, light, silvery metal.
Discovery history
Potassium compounds, like its closest chemical analogue, sodium (cm. SODIUM), have been known since antiquity and have been used in various fields of human activity. However, these metals themselves were first isolated in a free state only in 1807 during the experiments of the English scientist G. Davy (cm. DEVI Humphrey)... Davy, using galvanic cells as a source of electric current, carried out electrolysis of potash melts (cm. POTASH) and caustic soda (cm. CAUSTIC SODA) and thus isolated metallic potassium and sodium, which he called "potassium" (hence the name potassium preserved in the English-speaking countries and France) and "sodium". In 1809 the English chemist L. V. Gilbert proposed the name "potassium" (from the Arabic al-kali - potash).
Being in nature
The potassium content in the earth's crust is 2.41% by mass, potassium is among the top ten most common elements in the earth's crust. Key minerals containing potassium: sylvin (cm. SILVIN) KCl (52.44% K), sylvinite (Na, K) Cl (this mineral is a tightly compressed mechanical mixture of crystals of potassium chloride KCl and sodium chloride NaCl), carnallite (cm. CARNALLIT) KCl MgCl 2 6H 2 O (35.8% K), various aluminosilicates (cm. ALUMOSILICATES) containing potassium, kainite (cm. KAINIT) KCl MgSO 4 3H 2 O, polyhalite (cm. POLIGALIT) K 2 SO 4 MgSO 4 2CaSO 4 2H 2 O, alunite (cm. ALUNITE) KAl 3 (SO 4) 2 (OH) 6. Seawater contains about 0.04% potassium.
Receiving
Currently, potassium is obtained by interacting with liquid sodium molten KOH (at 380-450 ° C) or KCl (at 760-890 ° C):
Na + KOH = NaOH + K
Potassium is also obtained by electrolysis of KCl melt mixed with K 2 CO 3 at temperatures close to 700 ° C:
2KCl = 2K + Cl 2
Potassium is removed from impurities by vacuum distillation.
Physical and chemical properties
Metallic potassium is soft, easy to cut with a knife and amenable to pressing and rolling. Has a cubic body-centered cubic lattice, the parameter a= 0.5344 nm. The density of potassium is less than the density of water and is equal to 0.8629 g / cm 3. Like all alkali metals, potassium melts easily (melting point 63.51 ° C) and begins to evaporate even at relatively low heating (boiling point of potassium 761 ° C).
Potassium, like other alkali metals, is chemically very reactive. It easily interacts with atmospheric oxygen to form a mixture, mainly consisting of K 2 O 2 peroxide and KO 2 superoxide (K 2 O 4):
2K + O 2 = K 2 O 2, K + O 2 = KO 2.
When heated in air, potassium burns with a violet-red flame. With water and dilute acids, potassium interacts with an explosion (the resulting hydrogen ignites):
2K + 2H 2 O = 2KOH + H 2
Oxygen-containing acids can be reduced during this interaction. For example, the sulfur atom of sulfuric acid is reduced to S, SO 2 or S 2–:
8K + 4H 2 SO 4 = K 2 S + 3K 2 SO 4 + 4H 2 O.
When heated to 200-300 ° C, potassium reacts with hydrogen to form a salt-like hydride KH:
2K + H 2 = 2KH
With halogens (cm. HALOGENS) potassium interacts with an explosion. It is interesting to note that potassium does not interact with nitrogen.
Like other alkali metals, potassium readily dissolves in liquid ammonia to form blue solutions. In this state, potassium is used for some reactions. During storage, potassium slowly reacts with ammonia to form the amide KNH 2:
2K + 2NH 3 fl. = 2KNH 2 + H 2
The most important potassium compounds are K 2 O oxide, K 2 O 2 peroxide, K 2 O 4 superoxide, KOH hydroxide, KI iodide, K 2 CO 3 carbonate and KCl chloride.
Potassium oxide K 2 O is usually obtained indirectly through the reaction of peroxide and metallic potassium:
2K + K 2 O 2 = 2K 2 O
This oxide exhibits pronounced basic properties, easily reacts with water to form potassium hydroxide KOH:
K 2 O + H 2 O = 2KOH
Potassium hydroxide, or caustic potassium, is readily soluble in water (up to 49.10% by weight at 20 ° C). The resulting solution is a very strong base, related to alkalis ( cm. ALKALI). KOH reacts with acidic and amphoteric oxides:
SO 2 + 2KOH = K 2 SO 3 + H 2 O,
Al 2 O 3 + 2KOH + 3H 2 O = 2K (this is how the reaction proceeds in solution) and
Al 2 O 3 + 2KOH = 2KAlO 2 + H 2 O (this is how the reaction proceeds when the reagents are melted).
In industry, potassium hydroxide KOH is obtained by electrolysis of aqueous solutions of KCl or K 2 CO 3 using ion-exchange membranes and diaphragms:
2KCl + 2H 2 O = 2KOH + Cl 2 + H 2,
or due to exchange reactions of solutions of K 2 CO 3 or K 2 SO 4 with Ca (OH) 2 or Ba (OH) 2:
K 2 CO 3 + Ba (OH) 2 = 2KOH + BaCO 3
Contact with solid potassium hydroxide or drops of its solutions on the skin and eyes causes severe burns to the skin and mucous membranes; therefore, work with these caustic substances should only be done with protective glasses and gloves. During storage, aqueous solutions of potassium hydroxide destroy glass, melts destroy porcelain.
Potassium carbonate K 2 CO 3 (the common name is potash) is obtained by neutralizing a potassium hydroxide solution with carbon dioxide:
2KOH + CO 2 = K 2 CO 3 + H 2 O.
Potash is found in significant amounts in the ash of some plants.
Application
Metallic potassium is a material for electrodes in chemical current sources. An alloy of potassium with another alkali metal - sodium is used as a heat carrier (cm. HEAT CARRIER) in nuclear reactors.
On a much larger scale than metallic potassium, its compounds are used. Potassium is an important component of the mineral nutrition of plants, they need it in significant quantities for normal development, therefore potash fertilizers are widely used (cm. POTASSIUM FERTILIZERS): potassium chloride KCl, potassium nitrate, or potassium nitrate, KNO 3, potash K 2 CO 3 and other potassium salts. Potash is also used in the production of special optical glasses, as an absorber of hydrogen sulfide in the purification of gases, as a dehydrating agent and in tanning leather.
As medicinal product potassium iodide KI finds application. Potassium iodide is also used in photography and as a micronutrient fertilizer. A solution of potassium permanganate KMnO 4 ("potassium permanganate") is used as an antiseptic.
According to the content of radioactive 40 K in rocks, their age is determined.
Potassium in the body
Potassium is one of the most important nutrients (cm. BIOGENIC ELEMENTS), constantly present in all cells of all organisms. Potassium ions K + are involved in the work of ion channels (cm. ION CHANNELS) and regulation of the permeability of biological membranes (cm. BIOLOGICAL MEMBRANES), in the generation and conduct of a nerve impulse, in the regulation of the activity of the heart and other muscles, in various metabolic processes. The content of potassium in tissues of animals and humans is regulated by steroid hormones of the adrenal glands. On average, the human body (body weight 70 kg) contains about 140 g of potassium. Therefore, for normal life with food, the body should receive 2-3 g of potassium per day. Foods such as raisins, dried apricots, peas and others are rich in potassium.
Features of handling potassium metal
Potassium metal can cause very severe skin burns, if the smallest particles of potassium get into the eyes, severe lesions with loss of vision occur, therefore, you can only work with metal potassium with protective gloves and goggles. The ignited potassium is poured with mineral oil or covered with a mixture of talc and NaCl. Store potassium in hermetically sealed iron containers under a layer of dehydrated kerosene or mineral oil.

encyclopedic Dictionary. 2009 .

See what "potassium" is in other dictionaries:

Potassium 40 ... Wikipedia

Novolatinsk. kalium, from the Arab. kali, alkali. The soft and light metal that makes up the potassium base. Discovered by Devi in ​​1807. An explanation of the 25,000 foreign words that have come into use in the Russian language, with the meaning of their roots. Mikhelson A.D., 1865. ... ... Dictionary of foreign words of the Russian language

- (Kalium), K, chemical element of group I of the periodic table, atomic number 19, atomic mass 39.0983; refers to alkali metals; tm 63.51shC. In living organisms, potassium is the main intracellular cation, is involved in the generation of bioelectric ... ... Modern encyclopedia

POTASSIUM- (Kalium, s. Potassium), chem. element, char. K, atomic number 19, silvery white, lustrous metal, having the density of wax at ordinary ta; opened by Devi in ​​1807, Ud. v. at 20 ° 0.8621, atomic weight 39.1, monovalent; melting point ... Great medical encyclopedia

Potassium- (Kalium), K, chemical element of group I of the periodic table, atomic number 19, atomic mass 39.0983; refers to alkali metals; m.p. 63.51 ° C. In living organisms, potassium is the main intracellular cation, is involved in the generation of bioelectric ... ... Illustrated Encyclopedic Dictionary

- (symbol K), a common chemical element related to ALKALINE METALS. It was first isolated by Sir Humphrey Davy in 1807. Its main ores are sylvite (potassium chloride), carnallite and polyhalite. Potassium is a coolant in NUCLEAR ... Scientific and technical encyclopedic dictionary

Husband. potasium, the metal that makes up the base of potassium, very similar to sodium (sodium). Kali Wed, neskl., Vegetable alkali or alkaline salt; potassium carbonate, pure potash. Potassium, related to potassium. Calisty containing potassium. Sensible ... ... Dahl's Explanatory Dictionary - POTASSIUM, potassium, pl. no, husband., and kali, neskl., cf. (Arabic potash) (chem.). The chemical element is a silvery white alkali metal extracted from carbonate salt. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

DEFINITION

Potassium- the nineteenth element of the Periodic Table. The designation is K from the Latin "kalium". Located in the fourth period, IA group. Refers to metals. The nuclear charge is 19.

Potassium does not occur naturally in a free state. The most important potassium minerals are: sylvinite KCl, sylvinite NaCl × KCl, carnallite KCl × MgCl 2 × 6H 2 O, kainite KCl × MgSO 4 × 3H 2 O.

As a simple substance, potassium is a shiny silver-gray metal (Fig. 1) with a body-centered crystal lattice. Exceptionally reactive metal: quickly oxidizes in air, forming friable reaction products.

Rice. 1. Potassium. Appearance.

Atomic and molecular weight of potassium

Relative molecular weight of the substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms of a chemical element is more than 1/12 of the mass of a carbon atom.

Since in the free state potassium exists in the form of monatomic K molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 39.0983.

Potassium isotopes

It is known that in nature, potassium can be in the form of two stable isotopes 39 K and 41 K. Their mass numbers are 39 and 41, respectively. The nucleus of the 39 K potassium isotope contains nineteen protons and twenty neutrons, while the 41 K isotope contains the same number of protons and twenty-two neutrons.

There are artificial isotopes of potassium with mass numbers from 32 to 55, among which the most stable is 40 K with a half-life of 1.248 × 10 9 years.

Potassium ions

At the external energy level of the potassium atom, there is one electron, which is valence:

1s 2 2s 2 2p 6 3s 2 3p 6 4s 1.

As a result of chemical interaction, potassium gives up its only valence electron, i.e. is its donor, and turns into a positively charged ion:

K 0 -1e → L +.

Molecule and atom of potassium

In a free state, potassium exists in the form of monatomic molecules L. Let us give some properties that characterize the atom and molecule of potassium:

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise

Calculate the mass of potassium hydroxide, which is required to prepare a 20 ml alkali solution (mass fraction of KOH 20%, density 1.22 g / ml).

Solution

Find the mass of the potassium hydroxide solution: K - Potassium POTASSIUM(lat. Kalium), K (read "potassium"), a chemical element with atomic number 19, atomic mass 39.0983. Potassium occurs naturally in the form of two stable nuclides: 39 K (93.10% by mass) and 41 K (6.88%), as well as one radioactive 40 K (0.02%). The half-life of potassium-40 T 1/2 is about 3 times less than T 1/2 of uranium-238 and is 1.28 billion years. At b the decay of potassium-40 forms stable calcium-40, and during decay by the type of electron capture, an inert gas argon-40 is formed. 2K + 2H 2 O = 2KOH + H 2 8K + 4H 2 SO 4 = K 2 S + 3K 2 SO 4 + 4H 2 O. When heated to 200-300 ° C, potassium reacts with hydrogen (H) to form salt-like hydride KH: Receiving: currently, potassium is obtained by interacting with liquid sodium (Na) molten KOH (at 380-450 ° C) or KCl (at 760-890 ° C): Na + KOH = NaOH + K Potassium is also obtained by electrolysis of KCl melt mixed with K 2 CO 3 at temperatures close to 700 ° C: 2KCl = 2K + Cl 2 Potassium is removed from impurities by vacuum distillation. Application: metallic potassium is a material for electrodes in chemical current sources. An alloy of potassium with another alkali metal - sodium (Na) is used as a coolant in nuclear reactors. On a much larger scale than metallic potassium, its compounds are used. Potassium is an important component of the mineral nutrition of plants (this takes about 90% of the extracted potassium salts), they need it in significant quantities for normal development, therefore potassium fertilizers are widely used: potassium chloride KCl, potassium nitrate, or potassium nitrate, KNO 3, potash K 2 CO 3 and other potassium salts. Potash is also used in the production of special optical glasses, as an absorber of hydrogen sulfide in the purification of gases, as a dehydrating agent and in tanning leather. Potassium iodide KI is used as a medicine. Potassium iodide is also used in photography and as a micronutrient fertilizer. A solution of potassium permanganate KMnO 4 ("potassium permanganate") is used as an antiseptic. Biological role: potassium is one of the most important biogenic elements that is constantly present in all cells of all organisms. Potassium ions K + are involved in the work of ion channels and regulation of the permeability of biological membranes, in the generation and conduction of nerve impulses, in the regulation of the activity of the heart and other muscles, in various metabolic processes. The content of potassium in tissues of animals and humans is regulated by steroid hormones of the adrenal glands. On average, the human body (body weight 70 kg) contains about 140 g of potassium. Therefore, for normal life with food, the body should receive 2-3 g of potassium per day. Foods such as raisins, dried apricots, peas and others are rich in potassium. Potassium is an element that is in the periodic system of Mendeleev under the 19th number. The substance is usually denoted capital letter K (from Latin Kalium). In the Russian chemical nomenclature, the real name of the element appeared thanks to G.I. Hess in 1831. Initially, potassium was called "al-kali", which means "plant ash" in Arabic. It was caustic potassium that became the material for the very first production of the substance. Caustic potassium, in turn, was extracted from potash, which was a plant combustion product (potassium carbonate). H. Davy became its discoverer. It should be noted that potassium carbonate is the prototype of a modern detergent. It was later used for fertilizers used in agriculture, in the production of glass and other purposes. At present, potash is food supplement, which passed the official registration, and they learned to extract potassium in completely different ways. In nature, potassium can only be found in the form of compounds with other elements (for example, sea ​​water, or minerals), its free form does not occur at all. It is capable of oxidizing in the open air in a fairly short period of time, as well as entering into chemical reactions (for example, when potassium interacts with water, alkali is formed). Table 1 Reserves of potash salts (million tons in terms of k2o) and the average content of k2o in ores,% Country, part of the world General stocks Reserves confirmed Their% of the world Average content 1 2 3 4 5 Russia 19118 3658 31,4 17,8 Europe 3296 2178 18,5 - Belarus 1568 1073 9,1 16 United Kingdom 30 23 0,2 14 Germany 1200 730 6,2 14 Spain 40 20 0,2 13 Italy 40 20 0,2 11 Poland 10 10 0,1 12 Ukraine 375 292 2,5 11 France 33 10 0,1 15 Asia 2780 1263 10,8 - Israel 600 44 0,4 1,4 Jordan 600 44 0,4 1,4 Kazakhstan 102 54 0,5 8 China 320 320 2,7 12 Thailand 150 75 0,6 2,5 Turkmenistan 850 633 5,4 11 Uzbekistan 159 94 0,8 12 Africa 179 71 0,6 - Congo 40 10 0,1 15 Tunisia 34 19 0,2 1,5 Ethiopia 105 42 >0,4 25 14915 4548 38,7 - Argentina 20 15 0,1 12 Brazil 160 50 0,4 15 Canada 14500 4400 37,5 23 Mexico 10 - 0 12 USA 175 73 0,6 12 Chile 50 10 0,1 3 Total: 40288 11744 100 - Description of potassium Potassium as a simple substance is an alkali metal. It is characterized by a silvery-white color. Shine instantly appears on a fresh surface. Potassium is a soft metal that melts easily. If the substance or its compounds are placed in a burner flame, then the fire will acquire a pink-violet color. Physical properties of potassium Potassium is a very soft metal that can be easily cut with an ordinary knife. Its Brinell hardness is 400 kn / m 2 (or 0.04 kgf / mm 2). It has a body-centered cubic crystal lattice (5 = 5.33 A). Its density is 0.862 g / cm 3 (20 0 С). The substance begins to melt at a temperature of 63.55 0 С, boil at 760 0 С. It has a coefficient of thermal expansion equal to 8.33 * 10 -5 (0-50 0 С). Its specific heat at a temperature of 20 ° C is 741.2 J / (kg * K) or 0.177 cal / (g * 0 C). At the same temperature, it has a specific electrical resistance equal to 7.118 * 10 -8 ohm * m. The temperature coefficient of the electrical resistance of the metal is 5.8 * 10 -15. Potassium forms crystals of a cubic system, space group I m3m, cell parameters a= 0.5247 nm, Z = 2. Chemical properties Potassium is an alkali metal. In this regard, the metallic properties of potassium are typically manifested in the same way as other similar metals. The element exhibits its strong chemical activity, and in addition, it also acts as a strong reducing agent.As mentioned above, the metal actively reacts with air, as evidenced by the appearance of films on its surface, as a result of which its color becomes dull. This reaction can be observed with the naked eye. If potassium is in contact with the atmosphere for a sufficiently long time, then there is a possibility of its complete destruction. Upon reaction with water, a characteristic explosion occurs. This is due to the release of hydrogen, which ignites with a characteristic pinkish-violet flame. And when phenolphthalein is added to water that reacts with potassium, it acquires a crimson color, which indicates an alkaline reaction of the resulting potassium hydroxide (KOH). When a metal interacts with elements such as Na, Tl, Sn, Pb, Bi, intermetallic compounds are formed The specified characteristics of potassium indicate the need to comply with certain safety rules and conditions during storage of the substance. So, the substance should be covered with a layer of gasoline, kerosene or silicone. This is done to completely exclude its contact with air or water. It should be noted that at room temperature, the metal reacts with halogens. If you heat it a little, then it easily interacts with sulfur. If the temperature rises, potassium is able to combine with selenium and tellurium. If the temperature is raised to more than 200 0 C in a hydrogen atmosphere, then KH hydride is formed, which is capable of igniting without outside help, i.e. on one's own. Potassium does not interact with nitrogen at all, even if proper conditions are created for this (elevated temperature and pressure). However, these two substances can be made to come into contact by affecting them with an electric discharge. In this case, you get potassium azide KN 3 and potassium nitride K 3 N. If graphite and potassium are heated together, the result is carbides KC 8 (at 300 ° C) and KC 16 (at 360 ° C). When potassium and alcohols interact, alcoholates are obtained. In addition, potassium makes the process of polymerization of olefins and diolefins much faster. Haloalkyls and haloaryls together with the nineteenth element give potassium alkyls and potassium aryls. Table 2. Chemical properties of potassium Characteristic Meaning Atom properties Name, symbol, number Potassium / Kalium (K), 19 Atomic mass (molar mass) 39.0983 (1) a. e.m. (g / mol) Electronic configuration 4s1 Atom radius 235 pm Chemical properties Covalent radius 203 pm Ion radius 133 pm Electronegativity 0.82 (Pauling scale) Electrode potential −2.92 V Oxidation states 0; +1 Ionization energy (first electron) 418.5 (4.34) kJ / mol (eV) Thermodynamic properties of a simple substance Density (at n.o.) 0.856 g / cm³ Melting temperature 336.8K; 63.65 ° C Boiling temperature 1047K; 773.85 ° C Ud. heat of fusion 2.33 kJ / mol Ud. heat of vaporization 76.9 kJ / mol Molar heat capacity 29.6 J / (K mol) Molar volume 45.3 cm³ / mol Crystal lattice of a simple substance Lattice structure Cubic body-centered Lattice parameters 5.332 Å Debye temperature 100 K The electronic structure of the potassium atom Potassium has a positively charged atomic nucleus (+19). In the middle of this atom there are 19 protons and 19 neutrons, which are surrounded by four orbits, where 19 electrons are in constant motion. The electrons are distributed in the orbitals in the following order: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 . At the outer energy level of a metal atom, there is only 1 valence electron. This explains the fact that absolutely in all compounds potassium has a valence of 1. Unlike lithium and sodium, this electron is located at a farther distance from the atomic nucleus. This is the reason for the increased chemical activity of potassium, which cannot be said about the two mentioned metals. Thus, the outer electron shell of potassium is represented by the following configuration: Despite the presence of vacancies 3 p- and 3 d-orbitals, there is no excited state. Recommended to read Tablets If you dreamed that you were crying from deceiving scammers Office programs Jokes about photographers in stories and photographs Jokes about photographers Android instructions Features of studying in Finland What you need to study in Finland Smartphones What do you need to know and do to make food beneficial? 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