ALKALI METALS

From Big Medical Encyclopedia

ALKALI METALS — IA chemical elements of group of a periodic system of D. I. Mendeleyev. Treat alkali metals lithium (see), sodium (see), potassium (see), rubidium (see), caesium (see), francium. Potassium and to a lesser extent sodium are the main intracellular cations, and also necessary components of the extracellular environment of all live organisms, participate in implementation of the major vital signs, play a special role as potentsialoobrazuyushchy ions in biol. membranes (see Membranes biological). Sodium plays a cardinal role in a water salt metabolism (see) the person and animals, together with potassium participates in emergence and transfer of nervous impulse (see), influences a condition of muscular and cardiovascular systems. Salts and other compounds of lithium, sodium and potassium in medicine are used as pharmaceuticals. Sodium chloride is foodstuff (see. Sodium chloride).

y. m have close physical and chemical properties, in the connections show valency + 1. These are the metals of silver-white color, low density which are characterized by the high chemical activity increasing from lithium to caesium; they vigorously interact with water (with ignition or explosion), oxygen (easily light up on air), halogens, during the heating react with hydrogen, sulfur and other elements. Are dissolved in liquid ammonia and the lowest aliphatic amines.

Lithium (Lithium, Li), sequence number 3, atomic weight (weight) 6,941; crust contains a lity 3,2-10 "3% (on weight), in water of the World Ocean of 1,5-10-5%. In a stand-at-ease in the nature does not meet, is a part of a large number of minerals, £пл ° 180,5 °, * °kits1317 °. Lithium belongs to biol. to microelements (see), in biological systems can replace sodium, however out of a cell it is brought by 10 — 25 times more slowly than sodium. Influence of lithium on exchange of biogenic amines (see Catecholamines) in c is established. N of page, and also on activity of adenylatecyclase (KF 4.6.1.1) and concentration glutaminic and at - aminobutyric to - t in a brain. As medicine most often use lithium carbonate (Lithium carbonicum).

Sodium (Natrium, Na), sequence number 11, atomic weight 22,9898; in crust is held sodium of 2,5% (on weight), in the soil — apprx. 0,63%, in water of the World Ocean on average of 1,035%, in living material on average of 0,02%, in a body of the person of 0,1 — 0,15%. In a stand-at-ease in the nature sodium does not meet, hl are eurysynusic. obr. its salts; £ °pl sodium 97,83 °, t°Kma 882,9 °. Sodium — one of the basic biological chemical elements (see).

Potassium (Kalium, To), sequence number 19, atomic weight 39,102; contains in crust potassium of 2,5% (on weight), in a human body the content of the general potassium makes 160 — 250 g, apprx. 98% of all potassium is in cells. In a stand-at-ease in the nature does not meet, the hl is widespread. obr. in the form of the salts which are a part of minerals; £пл 63,5 °, £нип 760 °. Potassium — one of the main biol. chemical elements.

Rubidium (Rubidium, Rb), sequence number 37, atomic weight 85,4678, content in crust

of 1,5*10-2% (on weight), does not form own minerals, £ °pl 39,5 °, * °kip 685 °. Rubidium — the constant satellite of potassium in the nature; the human body contains 0,68 g of this element therefore rubidium on weight appears on one of the first places among microelements. With age the content of rubidium in blood increases and by 15 — 20 years reaches the highest sizes (apprx. 0,0003%), however concentration of rubidium in blood considerably fluctuates depending on receipt of this element in an organism. Rubidium is used for production of photo cells, in instrument making, including in medical.

Caesium (Caesium, Cs), sequence number 55, atomic weight 132,905, content in crust 7,0 - • 10 ~ 4% (on weight), the most important mineral pollucite (Cs, Na) [AlSi206] * pn20; g°pltseziya 28,5 °, g°kip 705 °.

Caesium is a microelement, is used in electron-optical converters, in photo cells, etc. Radioisotopes of caesium apply as radiofarma-tsevtichesky drugs to radio-isotope diagnosis, and also contact and remote radiation therapy.

Francium (Francium, Fr), sequence number 87. It is open in 1939 when isotope 223Fr with half-life of 21,8 min. was found, is a part of a natural decay series of an actinouranium. At

crystallization francium is isomorphically besieged with salts of caesium. Bibliography: Kotton F. A. and Wil

kinson D. Fundamentals of inorganic chemistry, the lane with English, M., 1979; H e to r the expert about in B. V. Fundamentals of the general chemistry, t. 3, M., 1970; Hughes M. Inorganic chemistry of biological processes, the lane with English, M., 1983. A. V. Babkov.

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