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Radium and its decay products

Radium and its decay products are members of the uranium-238 radioactive family.

Radium (86Ra226)- metal, chemical properties analogue of barium.

The characteristics of radium and the main products of its decay are given in the table.

To obtain radon, highly soluble salts of radium mixed with barium are used, which do not contain traces of SO4 ions.

A solution of radium salt in distilled water containing HC1 releases 100% radon.

The separation of radium salt from a solution is influenced by the adsorption of radium by glass, which is noticeable at pH 6.5-4.5 and becomes negligible at pH 2.3.

Sulfates, carbonates, chromates, fluorides, oxalates and phosphates of radium are sparingly soluble. All salts of radium gradually decompose under the action of their own radiation, while they turn yellow, brown and orange.

Radon (86Ra222)- an inert gas, the highest homologue of xenon, has zero valence and does not give compounds due to ionic or atomic bonds. The radiological characteristics of radon are given in the table.

Radon is formed from the decay of radium. 1 Ci (37.103 MBq) of radon at a temperature of 0 °C and a pressure of 760 mm Hg. Art. occupies a volume of 0.65 mm3 and has a mass of 6.46. 10-6 g. This amount of radon is formed in a state of radioactive equilibrium from 1 g of radium. Radon is 7.6 times heavier than air. At temperatures from -62 to -65 ° C, radon passes into a liquid state, at a temperature from -110 to -113 ° C - into a solid state. Liquid radon is colorless at first, it becomes cloudy from decay products. Liquid radon causes green fluorescence on glass, while solid radon glows a bright blue-steel color. Part of the decay energy of radon is released in the form of heat (1 Ci of radon forms 29.8 cal/h).

Table. Basic radiological characteristics of isotopes of the Ra-226 series

In a closed volume between liquid and gaseous media, for example between water and air, radon is distributed according to Henry's law:

(1.4)

Or

(1.5)

where Qb and Ql are the amount of radon in the air and liquid, respectively, at steady state; Vb and Wl are the volumes of air and liquid; a is the distribution coefficient of radon in a given liquid compared to air (av = 1).

The solubility coefficient (a) of radon in water depends on its temperature.

For example, if the volume of water and air in a vessel are equal, then at a temperature of 20 ° C, 1/4 of the radon will be in the water, and 3/4 in the air, and with increasing water temperature, the value of a decreases. With mechanical mixing of water and air in a closed volume of 5.5 liters (5 liters of water and 0.5 liters of air), using the Malyutka pump with a capacity of 2-3 l / min, equilibrium is practically achieved in 5-10 minutes; in the static mixing mode, this requires 100 hours, in the convection mode - 64 hours. In one day, in the static mode, 0.676 of the maximum dissolving amount of radon is dissolved in water, in the convection mode - 820.

Radon solubility coefficient

Having a low coefficient of solubility in water and the ability to diffuse, radon easily passes from water into air when they are mixed in an open vessel, escaping from water into air the faster, the larger the area of ​​\u200b\u200btheir contact, the smaller the thickness of the water layer, the higher its temperature and the more intense the mixing of the water. The addition of salts to water reduces the solubility of radon, with an increase in salt concentration, the effect of temperature on the solubility of radon decreases and becomes insignificant at high salt concentrations.

In anhydrous solvents, radon dissolves much better than in water.

The solubility of radon in a mixture with other liquid solvents (for example, with alcohol) is not more, but less than theoretically calculated by the mixing rule. In mixtures of non-aqueous solvents, radon, on the contrary, dissolves better than in each individual component of the mixture. In biological media, radon also dissolves better than in water.

Radon is adsorbed on the surface of many solids. It is especially well absorbed by rubber, celluloid, wax, resin, silica gel, clay, sea foam and many other organic colloidal and polymeric substances. Blood dissolves radon twice as well as water. The best radon adsorbent is activated carbon, which absorbs a significant amount of radon even at ordinary temperatures.

With a decrease in the temperature of coal from -80 to -90 ° C, the adsorption of radon on it noticeably increases, at a temperature of liquid air, radon is adsorbed on coal almost completely and instantly. At a temperature of -140.7 °C (liquid air temperature), radon is completely condensed in a coil, through which a stream of dry air-radon mixture is passed. At a temperature of 300–400°C, radon adsorbed on carbon is almost completely desorbed.

Radon diffuses in air, liquids and some solids. The diffusion coefficient (D) of radon in air at normal temperature and pressure is 0.1 cm2/s.

Radon sorption parameters

The table shows the parameters of radon sorption from water by some materials that are used in technological equipment for working with radon. From this table it follows that glass and metals are most suitable for long-term storage of radon-containing media. Rigid organic polymeric materials are limitedly suitable for short-term storage of radon solutions, although they can be used for the manufacture of pipelines and devices in which radon media move at a sufficiently high speed or are continuously exchanged.

It also follows from the table that special care should be taken to use soft polymers and rubber to isolate radon environments, since these materials behave in relation to radon as organic solvents, their use should be accompanied by a sharp limitation of the area of ​​​​their contact with the radon environment, for example, only when isolating places joints of glass or metal tubes. Under certain circumstances, rubber or capron can be used as radon absorbers from water and air to obtain solid radon concentrates under normal conditions.

Table. Parameters of radon adsorption from water by some materials in static mode

(1.6)

where QRn is the amount of radon accumulated in the vessel; QRa is the amount of radium in the vessel in grams or curie; e is the base of the natural logarithm; λRn is the radon decay constant; t is the accumulation time.

The calculation of the value of QRn depending on t is usually carried out using tables of exponential functions.

In practice, radon comes into a state of radioactive equilibrium with radium four weeks after the vessel with radium is sealed. After the separation of radon from radium, the decay of radon is determined by the formula:

(1.7)

where N0 is the initial number of atoms; Nt is the number of atoms after time t.

During the decay of radon, RaA, RaB, RaC, RaC are successively formed from it, which are called short-lived daughter products of radon. The number of At218, Rn218 and RaC (T1210) isotopes formed during the decay is negligible and has no practical significance. Formulas are known that describe the accumulation and decay of the radioactive series of isotopes (RaA, RaB, RaC).

Radiological characteristics of isotopes

RaA (polonium isotope) in the presence of radon, in 20-30 minutes it comes with it practically into a state of radioactive equilibrium. Isolated from radon, RaA during the same time almost completely decays and passes into RaB.

RaB (lead isotope)- the longest living of the chain of short-lived daughter products of radon, so it determines the time for which it comes into equilibrium with radon (about 3 hours). During the same period, when separated from radon, the entire chain of short-lived daughter products of radon almost completely decays.

The decay of RaB produces RaC (an isotope of bismuth). During the decay of RaC, a series branching occurs, and almost all of its atoms (99.96%) turn into RaC, emitting beta particles, and only 0.04% pass into RaC, emitting alpha particles.

Short-lived daughter products have a number common properties. These are electrically charged atoms. heavy metals. In the air, they are in the form of free atoms or in combination with submicroscopic particles (less than 0.035 microns) - condensation nuclei. In the form of free atoms in the air, there are mainly RaA (90%) and RaB (10%) atoms, which are very mobile (diffusion coefficient 1-1.3 cm/s). The atoms associated with the condensation nuclei are less mobile - the diffusion coefficient is 0.045-0.015 cm/s. Free atoms, to a greater extent than bound ones, settle on various surfaces, forming an active plaque of radon daughter products. Their lifetime before settling on the surface and inactive aerosol particles does not exceed 10–60 s.

In an air-radon bath (ARB), almost 90% of the radon daughter products during the procedure (15-20 minutes) settle from the air onto the inner walls of the box, 5% remain in the air, and the rest settle on the skin of the patient in the bath.

Surfaces immersed in radon water are easily covered by the daughter products of radon deposited on them, especially when a body immersed in water moves; daughter products diffuse in water.

The ratio of the activity of radon and its daughter products in water and air can vary over a very wide range - from the radioactive equilibrium of the entire chain to the almost complete absence of daughter products in water and air.

The decay of short-lived products leads to the formation of the first long-lived decay product of radon - RaD.
RaD (an isotope of lead) has a much longer half-life (22 years) compared to RaC and therefore cannot come into radioactive equilibrium with it if they are isolated from Ra226.

The activity of RaD with the complete decay of radon atoms will be only 0.005 of the initial activity of radon. However, in older radium preparations, RaD can accumulate in significant amounts: for example, 1 g of radium in 22 years produces 500 mCi of RaD.

RaD becomes RaE (an isotope of bismuth). RaF (an isotope of polonium) is formed from it, from which, in turn, a stable lead isotope Pb206 is formed.

Polonium, like RaD, accumulates in old radium preparations. In equilibrium with 1 g of radium, 2.24 is accumulated. 10-4 g of polonium. Being a strong colloid former, polonium is very easily sorbed by dust, filters, dishes, etc. in a moderately acidic environment, has the ability to form big number complex compounds and easily sublimates at a temperature of 450 °C.

The radiation of radon and its daughter products has a significant effect on the surrounding substances. Glass (including quartz) under the influence of radioactive radiation gradually becomes brittle and changes its color. Radium solutions with their radiation decompose water with the formation of H2, O2, O3 and H2O2, i.e. with the formation of explosive gas. Radium in solution (1 g) releases from 0.5 to 1 cm3 of gas per hour.

In practice, there have been cases when an aqueous solution containing 0.5–0.6 g of radium salt, poured up to 3/4 of the volume into a sealed vessel, spontaneously exploded from prolonged (within a month) storage at room temperature. The main cause of the explosion was the insufficient space of the gas above the liquid. Explosions of sealed ampoules with radium salt are possible at the moment of their opening due to the accumulation of explosive gas in them.

Isotopes of the radium series are naturally distributed throughout the earth's surface. In this regard, radium, radon and its daughter products are found in soil, water and atmospheric air. The content of radon over land is on average 1. 10-13 Ci/l. In soil, the content of radon is usually 100 times higher. In the water of rivers, lakes and oceans, radon is practically absent due to favorable conditions for its transition into the atmosphere. in the waters sedimentary rocks radon is found in concentrations from 1.5 to 6. 10-11 Ci / l, radium - 2-3. 10-12 g/l.

In the waters of acidic igneous rocks, the average content of radon is 1 . 10-9 Ci / l, radium - 2-4. 10-12 g/l. In the waters of uranium deposits, the radon content averages 0.5-1. 10-8 Ci / l, radium - 6-8. 10-11 g/l. In high concentrations, radon is found in the waters of a number of radioactive healing springs, the mineral waters of which contain at least 5 nCi / l - 10 nCi / l of radon.

Uranium, radium, thorium

In addition to radon, in the water of some healing springs, uranium, radium, and thorium can be detected in elevated concentrations.

The content of radium or uranium in mineral water is admissible in twelvefold excess in relation to admissible of these isotopes in water of sources of drinking water supply. This is based on the fact that the use of drinking water in the resort does not exceed 1 month per year (drinking water is taken daily throughout life).
It follows from this that, in accordance with NRB-99, the content of radium in the mineral drinking water should not exceed 0.2. 10-9 Ci / l (7.2 Bq / l), and uranium - 37.2 Bq / l.

One way or another, the intake of these isotopes into the body with mineral water should not exceed the values ​​of the maximum annual intake given in NRB-99 (8.4 103 Bq/year and 6.7 102 Bq/year, respectively). In this regard, taking baths with a radium content above 0.2. 109 Ci/l is inappropriate.

In the Russian Federation, only the waters of Ukhta are not allowed for use in the practice of spa treatment (prohibited in the 30s of our century).

I.I. Gusarov

Marie Curie. Radioactivity and the elements [Matter's deepest secret] Paez Adela Munoz

PRODUCTION OF RADIUM AND POLEMIC AROUND POLONIUM

After Maria devoted several years to extracting radium, in early 1902 she managed to isolate a little more than a tenth of a gram (120 mg) of pure radium chloride, on the basis of which she established atomic mass radium, 225±1, which is quite close to its real value (226.03). Getting this minute amount required not only many years of work, but also an extraordinary knowledge of chemistry, taking into account the processes in which radium was involved. For the radioactive series shown in Rutherford and Soddy's table, the decay process never stops; any child element that comes from the decay of the parent element also decays, and both do so in a certain rhythm. Hence, the largest proportion between child and parent elements is given by the quotient of their half-lives. Since uranium (the parent element) is 4500 million years old and radium (the child element) is 1600 million years old, in a mineral that contains both of them, the largest ratio of radium/uranium that can be found is 1600/4470000000, that is 1/2800000, approximately 1 gram/3 tons.

However, Maria did not work with pure uranium, but with the remains of one of its ores, which were contaminated with various impurities, so that the largest proportion approached 1 gram of radium per 10 tons of material. On the other hand, radium and barium have very similar chemical properties, so some of the radium could well have been captured by barium, which, moreover, was present in a much larger proportion in the prototype. Worst of all, Maria did not know the nature of the processes associated with radioactivity, as well as the properties of radium and the reasons for its close relationship with uranium. Nor did she think that his concentration was so negligible. Perhaps if she had assumed such a thing, she simply would not have taken the job.

In this regard, obtaining 120 mg of radium chloride was a feat not only from a chemical point of view, but also from a physical and radiological point of view. In addition, Maria carried out most of the process herself, since as soon as Pierre was convinced of the existence of radium, he began to study the properties of the rays and their effects on the human body.

Some time after the isolation of radium chloride, Maria wrote to her father in Warsaw, informing him of this long-awaited news. Although his health was already severely undermined, Vladislav still found the strength to congratulate his daughter and joke that, judging by the efforts made, this is the most expensive element in the history of mankind. Vladislav died six days later, and Maria came to his funeral.

In December 1902, when it seemed that the problems with radium were already over (although in fact they were just beginning), a fierce controversy arose around polonium. German physicist Wilhelm Markwald of the University of Berlin published an article in which he claimed the discovery of a new chemical element. He called it radiotellurium because the chemical properties of the element were similar to those of tellurium from the oxygen group. This radio element was nothing more than polonium, which Mary gave the name in memory of her then existing country although this was not immediately clear. The controversy was unwittingly stirred up by Marie and Pierre, who, in a 1902 article, argued that polonium was a variety of bismuth and had not yet been proven to be a new element. Another article published by Pierre the following year stated that radium was the only radioactive element whose existence was unquestionably proven. However, Maria did not support this overly painful reaction to Marwald's discovery. In addition, the German scientist was encouraged by the assertion made by the Curies that the activity of polonium was slowly decreasing, while the activity of its radiotellurium remained constant.

Markwald had access to large quantities of pitchblende residues in Joachimsthal and had the best tools in his laboratory. However, by repeating Maria's procedure to isolate a new element, using successive precipitations, the scientist did not obtain radiotellurium in its pure form and used electrochemical methods which led to victory where Mary failed. In this way, Markwald was able to obtain a small amount of the pure substance. He placed radiotellurium in the group periodic table, which actually corresponds to it, is the oxygen group. A few months after Marwald's paper appeared, Maria dismissively dismissed the name in an appendix to her doctoral dissertation: "Choosing a new name for this substance is nonsense, given what is known to date."

But the matter did not end there. It took Mary nine months of intense work to refute Marwald's arguments. At first, she doubted the invariance of radiotellurium activity over a sufficiently long period. Maria was also supported by Frederick Soddy, who, in an article published in 1904, remarked to Marwald that the constancy of radioactivity contradicted what was known at that time about radioactive substances. Soddy also argued that most scientists would agree with Maria's arguments that there was a clear attempt to give a new name to polonium. Finally, Soddy provided the final argument that meant Mary's victory, the radioactive decay law.

Having repeated and supplemented his experiments, Marwald was convinced that Maria and Soddy were right: the activity of radiotellurium decreases with time. He determined that the element had a half-life of 139.8 days. In turn, Maria, on the basis of five samples obtained by precipitation, and another obtained by "a very suitable method of electrolysis" proposed by Markwald, determined that for polonium this period is 140 days. Maria concluded: this definitely proves that we are talking about the same element. Since she was not a member of the French Academy of Sciences, Pierre, who was eventually accepted there, took over the presentation of these results on her behalf, which happened on January 29, 1906, and this was his last scientific communication before his death. In addition, Maria published a retraction in German to prove to Marwald's compatriots how wrong he was. In the end, Markwald nobly abandoned the name "radiotellurium" and settled for "polonium". Trying to hide his vulnerability, the German physicist somewhat ironically quoted the words of William Shakespeare:

What does the name mean? A rose smells like a rose, whether you call it a rose or not.

But polonium no doubt had something of radiotellurium, since, as we have said, tellurium and polonium are in the same group of the periodic table. Since then, it has been accepted that the half-life is a suitable indicator for the identification of a radio element.

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Radium(lat. radium), ra, radioactive chemical element group II periodic system Mendeleev, atomic number 88. R. isotopes with mass numbers 213, 215, 219-230 are known. The longest-lived is a-radioactive 226 ra with a half-life of about 1600 years. In nature as members of the natural radioactive series there are 222 ra (the special name of the isotope is actinium-x, symbol acx), 224 ra (thorium-x, thx), 226 ra and 228 ra (mesothorium-i, msthi).

The discovery of R. was reported in 1898 by the spouses P. and M. Curie together with J. Bemont shortly after A. becquerel For the first time (in 1896) he discovered the phenomenon of radioactivity on uranium salts. In 1897, working in Paris, M. Sklodowska-Curie found that the intensity of radiation emitted by uranium pitch (mineral uraninite), much higher than would be expected given the uranium content of the tar. Sklodowska-Curie suggested that this was due to the presence of still unknown highly radioactive substances in the mineral. Careful chemical research uranium pitch made it possible to discover two new elements - first polonium, and a little later - and R. During the allocation of R., the behavior of the new element was monitored by its radiation, which is why the element was named from lat. radius - ray. In order to isolate the pure compound R., the Curie couple processed about 1 t factory waste left after the extraction of uranium from uranium pitch. In particular, at least 10,000 recrystallizations from aqueous solutions of a mixture of bacl 2 and racl 2 (compounds barium serve the so-called. isomorphic carriers when extracting R.). As a result, we managed to get 90 mg clean raci 2.

In the USSR, work on the isolation of R. from domestic raw materials began shortly after October revolution 1917 on the direct orders of V. I. Lenin. The first preparations of R. were obtained in the USSR in 1921 by V. G. Khlopin and I. Ya. Bashilov. Samples of R. salts were demonstrated in May 1922 to participants in the Third Mendeleev Congress.

R. is an extremely rare element. AT uranium ores, which are its main source, by 1 t u accounts for no more than 0.34 G ra. R. belongs to highly scattered elements and is found in very small concentrations in a wide variety of objects.

All compounds R. in the air have a pale bluish glow. Due to self-absorption of a - and b -particles emitted at radioactive decay 226 ra and its daughter products, each gram of 226 ra releases about 550 j (130 feces) heat per hour, so the temperature of R.'s preparations is always slightly higher than the ambient temperature.

R. is a silvery-white lustrous metal that quickly tarnishes in air. Body-centered cubic lattice, calculated density 5.5 g/cm 3 . According to various sources, t sq. is 700-960 ° C, t kip about 1140 °С. On the outside electron shell atom R. there are 2 electrons (configuration 7 s 2). In accordance with this, R. has only one oxidation state, +2 (valence ii). By chemical properties, R. is most similar to barium, but is more active. At room temperature, R. combines with oxygen, giving the oxide rao, and with nitrogen, giving the nitride ra 3 n 2 . R. reacts violently with water, releasing h 2 , and forms strong base ra (oh) 2 . Chloride, bromide, iodide, nitrate, and R. sulfide are readily soluble in water; carbonate, sulfate, chromate, and oxalate are poorly soluble.

The study of the properties of R. has played a huge role in the development of scientific knowledge, because. made it possible to clarify many questions related to the phenomenon radioactivity. For a long time, R. was the only element whose radioactive properties found practical application (in medicine; for the preparation of luminous compositions, etc.). Today, however, in most cases it is more advantageous to use not radioactive but cheaper artificial radioactive isotopes of other elements. R. retained some importance in medicine as a source radon in the treatment of radon baths. In small quantities, R. is spent on the preparation of neutron sources (mixed with beryllium) and in the production of light compositions (mixed with zinc sulfide).

Lit.: Vdovenko V. M., Dubasov Yu. V., Analytical chemistry radium, L., 1973; Pogodin S. A., Libman E. P., How Soviet radium was obtained, M., 1971.

S. S. Berdonosov.

Radium in the body. Of the natural radioactive isotopes, the largest biological significance has a long-lived 226 ra. R. unevenly distributed in different areas biosphere. Exist geochemical provinces with a high content of R. The accumulation of R. in the organs and tissues of plants is subject to the general patterns of absorption of mineral substances and depends on the type of plant and the conditions of its growth. As a rule, there is more R. in the roots and leaves of herbaceous plants than in the stems and reproductive organs; most R. in the bark and wood. The average content of R. in flowering plants is 0.3-9.0? 10-11 curie/ kg, into the sea algae 0.2-3.2? 10-11 curie/ kg.

It enters the body of animals and humans with food in which it is constantly present (in wheat 20-26 × 10-15 G/ G, in potatoes 67-125 ? 10 -15 G/ G, in meat 8 ? 10 -15 G/ G) , and also with drinking water. The daily intake of 226 ra in the human body with food and water is 2.3? 10-12 curie, and losses with urine and feces 0.8? 10 -13 and 2.2? 10-12 curie. Approximately 80% of the R. that enters the body (it is close in chemical properties to ca) accumulates in the bone tissue. R.'s maintenance in a human body depends on the area of ​​residence and character of food. Large concentrations of R. in the body have a harmful effect on animals and humans, causing painful changes in the form osteoporosis, spontaneous fractures, tumors. R.'s content in the soil over 1? 10-7 - 10 -8 curie/ kg markedly inhibits the growth and development of plants.

Lit.: Vernadsky V.I., On the concentration of radium by plant organisms, “Dokl. Academy of Sciences of the USSR. Ser. A", 1930, No. 20; Radioecological research in natural biogeocenoses, M., 1972.

V. A. Kalchenko, V. A. Shevchenko.

Story

Receipt

Getting pure radium at the beginning of the 20th century cost a lot of work. Marie Curie worked for 12 years to obtain a grain of pure radium. To get just 1 g of pure radium, you needed several wagons of uranium ore, 100 wagons of coal, 100 water tanks and 5 wagons of various chemical substances. Therefore, at the beginning of the 20th century, there was no more expensive metal in the world. For 1 g of radium it was necessary to pay more than 200 kg of gold.

Radium is usually mined from uranium ores. In ores old enough to establish secular radioactive equilibrium in the uranium-238 series, there are 333 milligrams of radium-226 per ton of uranium.

There is also a method for extracting radium from radioactive natural waters that leach radium from uranium-bearing minerals. The content of radium in them can reach up to 7.5×10 −9 g/g. Thus, from 1931 to 1956, on the site of the current village of Vodny in the Ukhta region of the Komi Republic, the only enterprise in the world operated, where radium was isolated from the underground mineralized waters of the Ukhta deposit, the so-called "Water industry".

From the analysis of documents preserved in the archives of the successor of this plant (OAO Ukhta Electroceramic Plant "Progress"), it was calculated that approximately 271 g of radium had been released at the "Water industry" before the closure. In 1954, the world's supply of mined radium was estimated at 2.5 kg. Thus, by the beginning of the 1950s, approximately one in ten grams of radium had been produced at Vodnoy Promysly.

Physical and chemical properties

Radium is a lustrous white metal under normal conditions, darkening in air (probably due to the formation of radium nitride). Reacts with water. It behaves similarly to barium and strontium, but is more reactive. The usual oxidation state is +2. Radium hydroxide Ra(OH) 2 is a strong, corrosive base.

Due to the strong radioactivity, all radium compounds glow with a bluish light (radiochemiluminescence), which is clearly visible in the dark, and in aqueous solutions its salts undergo radiolysis.

Application

Today, radium is sometimes used in compact neutron sources by alloying small amounts of it with beryllium. Under the action of alpha radiation (helium-4 nuclei), neutrons are knocked out of beryllium:

9 B e + 2 4 α → 12 C + 1 n . (\displaystyle (\mathsf (^(9)Be+_(2)^(4)\alpha \to ^(12)C+^(1)n)).)

In medicine, radium is used as a source of radon for the preparation of radon baths (although their usefulness is currently disputed). In addition, radium is used for short-term exposure in the treatment of malignant diseases of the skin, nasal mucosa, and genitourinary tract.

However, at present there are many radionuclides with the desired properties that are more suitable for these purposes, which are obtained at accelerators or in nuclear reactors, for example, 60 Co ( T 1/2 = 5.3 years), 137 Cs ( T 1/2 = 30.2 years), 182 Ta ( T 1/2 = 115 days), 192 Ir ( T 1/2 = 74 days), 198 Au ( T 1/2 = 2.7 days) etc.

Until the 1970s, radium was often used to make permanently glowing luminous paints (for marking the dials of aviation and marine instruments, special watches and other devices), but now it is usually replaced by less dangerous isotopes: tritium ( T 1/2 = 12.3 years) or 147 Pm ( T 1/2 = 2.6 years). Sometimes watches with a radium light composition were also produced in civilian versions, including wristwatches. Also, radium phosphor in everyday life can be found in some old Christmas decorations, toggle switches with illuminated lever tip, on the scales of some old radios, and so on. characteristic feature Soviet-made permanent light composition - mustard yellow paint, although sometimes the color can be different (white, greenish, dark orange, etc.). The danger of such devices is that they did not contain warning labels; they can only be detected by dosimeters. Also, the phosphor degrades over the years and the paint often ceases to glow by our time, which, of course, does not make it less dangerous, since radium does not disappear anywhere. Another dangerous feature of radium phosphor mass is that over time the paint degrades and may begin to crumble, and a speck of such paint that has entered the body with food or when inhaled can cause great harm due to alpha radiation.

Biological role

Radium is extremely radiotoxic. In the body, it behaves like calcium - about 80% of the radium that enters the body accumulates in bone tissue. Large concentrations of radium cause osteoporosis, spontaneous bone fractures, and malignant tumors of bone and hematopoietic tissue. Radon, a gaseous radioactive decay product of radium, is also dangerous.

isotopes

There are 35 known isotopes of radium in the range of mass numbers from 201 to 235. Isotopes 223 Ra , 224 Ra , 226 Ra , 228 Ra are found in nature as members of the radioactive series uranium-238, uranium-235 and thorium-232. The remaining isotopes can be obtained artificially. Most of the known isotopes of radium undergo alpha decay into radon isotopes with a mass number 4 less than that of the parent nucleus. Neutron-deficient radium isotopes also have an additional beta decay channel with positron emission or orbital electron capture; in this case, an isotope of francium is formed with the same mass number as that of the parent nucleus. In neutron-rich isotopes of radium (mass number range from 227 to 235), only beta-minus decay was found; it occurs with the formation of nuclei