Uranium element. Properties, extraction, application and price of uranium. Chemical element uranium: properties, characteristics, formula. Extraction and use of uranium What letter denotes uranium in the periodic table

It is difficult to say what name the German scientist Martin Klaproth would have given to the element discovered in 1789 if an event had not occurred a few years earlier that excited all circles of society: in 1781, the English astronomer William Herschel, observing the starry sky with a homemade telescope, discovered a luminous cloud, which he at first mistook for a comet, but later became convinced that he was seeing a new, hitherto unknown seventh planet in the solar system. In honor of the ancient Greek god of the sky, Herschel named it Uranus. Impressed by this event, Klaproth gave the newborn element the name of the new planet.

About half a century later, in 1841, the French chemist Eugene Peligot managed to obtain metallic uranium for the first time. The industrial world remained indifferent to the heavy, relatively soft metal that turned out to be uranium. Its mechanical and Chemical properties did not attract either metallurgists or machine builders. Only Bohemian glassblowers and Saxon porcelain and faience craftsmen willingly used the oxide of this metal to give glasses a beautiful yellow-green color or decorate dishes with an intricate velvet-black pattern.

The ancient Romans knew about the "artistic abilities" of uranium compounds. During the excavations carried out near Naples, it was possible to find a glass mosaic fresco of amazing beauty. Archaeologists were amazed: for two millennia, the glass almost did not fade. When the glass samples were subjected to chemical analysis, it turned out that they contained uranium oxide, to which the mosaic owed its longevity. But, if the oxides and salts of uranium were engaged in "socially useful work", then the metal itself in pure form almost no one was interested.

Even scientists, and those were only very superficially familiar with this element. Information about him was scarce, and sometimes completely wrong. So, it was believed that its atomic weight is approximately 120. When D. I. Mendeleev created his Periodic system, this value confused all the cards for him: uranium, by its properties, did not want to fit into that cell of the table that was “reserved” for the element with this atomic weight. And then the scientist, contrary to the opinion of many of his colleagues, decided to accept the new value of the atomic weight of uranium - 240 and moved the element to the end of the table. Life has confirmed the correctness of the great chemist:

the atomic weight of uranium is 238.03.

But the genius of D. I. Mendeleev manifested itself not only in this. Back in 1872, when most scientists considered uranium a kind of “ballast” against the background of many valuable elements, the creator of the Periodic Table was able to foresee its truly brilliant future: “Among all known chemical elements, uranium stands out because it has the highest atomic weight ... The highest, known, the concentration of a mass of weighty substance ... existing in uranium ... must entail outstanding features ... Convinced that the study of uranium, starting from its natural sources, will lead to many more new discoveries, I boldly I recommend to those who are looking for subjects for new research to study uranium compounds with particular care.

The prediction of the great scientist came true in less than a quarter of a century: in 1896, the French physicist Henri Becquerel, while conducting experiments with uranium salts, made a discovery that rightfully belongs to the greatest scientific discoveries ever made by man. Here's how it happened. Becquerel has long been interested in the phenomenon of phosphorescence (i.e., luminescence) inherent in certain substances. Once the scientist decided to use for his experiments one of the salts of uranium, which chemists call the double sulfate of uranyl and potassium. On a photographic plate wrapped in black paper, he placed a patterned figure cut out of metal, coated with a layer of uranium salt, and exposed it to bright sunlight so that the phosphorescence was as intense as possible. Four hours later, Becquerel developed the plate and saw on it a distinct silhouette of a metal figure. Again and again he repeated his experiments - the result was the same. And on February 24, 1896, at the meetings of the French Academy of Sciences, the scientist reported that such a phosphorescent substance as double sulfate of uranyl and potassium, exposed to light, has invisible radiation that passes through black opaque paper and restores silver salts on a photographic plate.

Two days later, Becquerel decided to continue his experiments, but the weather was overcast, and without the sun, what kind of phosphorescence? Annoyed at the bad weather, the scientist hid the slides already prepared, but never exposed to illumination, along with samples of uranium salts, in a drawer of his desk, where they lay for several days. Finally, on the night of March 1, the wind cleared the Parisian sky of clouds and the sun's rays sparkled over the city in the morning. Becquerel, who was looking forward to this, hurried to his laboratory and took out the slides from his desk drawer to expose them to the sun. But, being a very pedantic experimenter, at the last moment he nevertheless decided to develop transparencies, although logic seemed to suggest that nothing could happen to him over the past days: after all, they were in a dark box, and without light not a single one phosphoresces. substance. At that moment, the scientist did not suspect that in a few hours ordinary photographic plates worth a few francs were destined to become a priceless treasure, and the day of March 1, 1896 would forever go down in the history of world science.

What Becquerel saw on the developed plates literally amazed him: the black silhouettes of the samples were sharply and clearly marked on the photosensitive layer. So, phosphorescence has nothing to do with it. But then, what kind of rays does the uranium salt emit? The scientist again and again makes similar experiments with other uranium compounds, including those that did not have the ability to phosphorescent or lay in a dark place for years, and each time an image appeared on the plates.

Becquerel has a still not entirely clear idea that uranium is "the first example of a metal that exhibits a property similar to invisible phosphorescence."

At the same time, the French chemist Henri Moissan managed to develop a method for obtaining pure metallic uranium. Becquerel asked Moissan for some uranium powder and found that the radiation of pure uranium is much more intense than that of its compounds, and this property of uranium remained unchanged under a variety of experimental conditions, in particular when heated strongly and when cooled to low temperatures.

With the publication of new data, Becquerel was in no hurry: he was waiting for Moissan to report on his very interesting research. Scientific ethics required this. And on November 23, 1896, at a meeting of the Academy of Sciences, Moissan made a report on the work to obtain pure uranium, and Becquerel spoke about a new property inherent in this element, which consisted in the spontaneous fission of the nuclei of its atoms. This property was called radioactivity.

The discovery of Becquerel marked the beginning of a new era in physics - the era of the transformation of elements. Once the atom was opened, it could no longer be considered one and indivisible—a path opened before science into the depths of this “brick” of the material world.

Naturally, now uranium has attracted the attention of scientists. At the same time, they were also interested in the following question: is radioactivity inherent only in uranium? Perhaps there are other elements in nature that have this property?

The outstanding physicists spouses Pierre Curie and Maria Skladowska-Curie were able to answer this question. With the help of a device designed by her husband, Marie Curie examined a huge amount of metals, minerals, salts. The work was carried out in extremely difficult conditions. The laboratory was an abandoned wooden shed, which the couple found in one of the Parisian courtyards. “It was a hut made of boards, with an asphalt floor and a glass roof that did not protect well from rain, without any adaptations,” M. Curie later recalled. - It contained only old wooden tables, a cast-iron stove that did not provide enough heat, and a blackboard that Pierre loved to use so much. There were no exhaust hoods for experiments with harmful gases, so these operations had to be done outside when the weather allowed, or indoors when open windows". In the diary of P. Curie there is an entry that sometimes the work was carried out at a temperature of only six degrees above zero.

Many problems arose with obtaining the necessary materials. Uranium ore, for example, was very expensive, and the Curies could not buy enough of it with their modest means. They decided to ask the Austrian government to sell them at a low price the waste of this ore, from which uranium was extracted in Austria, used in the form of salts for coloring glass and porcelain. The scientists were supported by the Vienna Academy of Sciences, and several tons of waste were delivered to their Paris laboratory.

Marie Curie worked with extraordinary perseverance. The study of various materials confirmed the correctness of Becquerel, who believed that the radioactivity of pure uranium is greater than any of its compounds. This was evidenced by the results of hundreds of experiments. But Marie Curie subjected to research more and more new substances. And suddenly... Surprise! Two uranium minerals, chalcolite and the tar ore of Bohemia, had a much more active effect on the device than uranium. The conclusion suggested itself: they contain some unknown element, characterized by an even higher ability to radioactive decay. In honor of Poland, the homeland of M. Curie, the couple named it polonium.

Back to work, again titanic work - and another victory: an element has been discovered that is hundreds of times more radioactive than uranium. Scientists named this element radium, which in Latin means "ray".

The discovery of radium to some extent distracted the scientific community from uranium. For about forty years, he did not really excite the minds of scientists, and engineering thought rarely indulged him with its attention. In one of the volumes of the technical encyclopedia, published in 1934, it was stated: "Elementary uranium has no practical application." The reputable publication did not sin against the truth, but after only a few years, life made significant adjustments to the ideas about the possibilities of uranium.

In early 1939, two scientific reports appeared. The first, sent to the French Academy of Sciences by Frédéric Joliot-Curie, was entitled "Experimental proof of the explosive fission of uranium and thorium nuclei under the action of neutrons." The second report, written by the German physicists Otto Frisch and Lise Meitner, was published by the English journal Nature; it was called: "The decay of uranium under the action of neutrons: a new kind of nuclear reaction." Both there and there it was about a new, hitherto unknown phenomenon that occurs with the nucleus of the heaviest element - uranium.

A few years before that, "little boys" had become seriously interested in uranium - that was the friendly name for a group of young talented physicists who worked under the direction of Enrico Fermi at the University of Rome. The hobby of these scientists was neutron physics, which contained many new and unknown things.

It was found that when irradiated with neutrons, as a rule, the nuclei of one element turn into the nuclei of another, which occupies the next cell in the Periodic system. And if the last, 92nd element, uranium, is irradiated with neutrons? Then an element should be formed, which is already in the 93rd place - an element that even nature could not create!

The kids liked the idea. Still, isn't it tempting to find out what an artificial element is, how it looks, how it behaves? So, uranium is irradiated. But what happened? In uranium, not one radioactive element appeared, as expected, but at least a dozen. There was some mystery in the behavior of uranium. Enrico Fermi sends a message about this to one of the scientific journals. Perhaps, he believes, the 93rd element was formed, but there is no exact evidence of this. But, on the other hand, there is evidence that some other elements are present in irradiated uranium. But what?

An attempt to answer this question was made by the daughter of Marie Curie, Irene Joliot-Curie. She repeated Fermi's experiments and carefully studied the chemical composition of uranium after irradiating it with neutrons. The result was more than unexpected: the element lanthanum appeared in uranium, located approximately in the middle of the periodic table, that is, very far from uranium.

When the same experiments were carried out by the German scientists Otto Hahn and Friedrich Strassmann, they found not only lanthanum but also barium in uranium. Riddle after riddle!

Hahn and Strassmann reported the experiments to their friend, the famous physicist Lise Meitner. Now several leading scientists are trying to solve the uranium problem at once. And so, first Frederic Joliot-Curie, and after some time Lisa Meitner come to the same conclusion: when a neutron hits, the uranium nucleus, as it were, falls apart. This explains the unexpected appearance of lanthanum and barium, elements with an atomic weight about half that of uranium.

American physicist Luis Alvarez, later laureate Nobel Prize, this news caught one January morning in 1939 in the hairdresser's chair. He was calmly looking through the newspaper, when suddenly a modest headline caught his eye: "Uranium Atom Divided into Two Halves."

A moment later, to the astonishment of the hairdresser and the customers waiting in line, a strange client ran out of the barbershop, half cut, with a napkin tied tightly around his neck and fluttering in the wind. Ignoring the astonished bystanders, the physicist raced to the UCLA lab where he worked to break the shocking news to his colleagues. Those at first were dumbfounded by the very original appearance of Alvarez waving a newspaper, but when they heard about the sensational discovery, they immediately forgot about his unusual hairstyle.

Yes, it was a real sensation in science. But Joliot-Curie also established another important fact: the decay of the uranium nucleus has the character of an explosion, in which the resulting fragments scatter to the sides with great speed. While it was possible to split only individual nuclei, the energy of the fragments only heated a piece of uranium. If the number of divisions is large, then a huge amount of energy will be released.

But where can one obtain such a quantity of neutrons to simultaneously bombard a large number of uranium nuclei with them? After all, the sources of neutrons known to scientists gave them many billions of times less than required. Nature itself came to the rescue. Joliot-Curie discovered that during the fission of a uranium nucleus, several neutrons fly out of it. Once in the nuclei of neighboring atoms, they must lead to a new decay - the so-called chain reaction will begin. And since these processes last for millionths of a second, colossal energy will immediately be released - an explosion is inevitable. It would seem that everything is clear. But after all, pieces of uranium have already been irradiated with neutrons more than once, but they did not explode, that is, a chain reaction did not occur. Apparently, some other conditions are needed. What? Frédéric Joliot-Curie could not yet answer this question.

And yet the answer was found. It was found in the same 1939 by young Soviet scientists Ya. B. Zeldovich and Yu. B. Khariton. In their work, they found that there are two ways to develop a nuclear chain reaction. First, it is necessary to increase the size of a piece of uranium, since when a small piece is irradiated, many newly released neutrons can fly out of it without encountering a single nucleus on their way. As the mass of uranium increases, the probability of a neutron hitting the target naturally increases.

There is another way: enriching uranium with the 235 isotope. The fact is that natural uranium has two main isotopes, the atomic weights of which are 238 and 235. In the nucleus of the first of them, which has 140 times more atoms, there are three neutrons more. Uranium-235, "poor" in neutrons, greedily absorbs them - much stronger than its "wealthy" brother, which does not even divide into parts, but turns into another element. This property of the isotope was later used by scientists to obtain artificial transuranium elements. For a chain reaction, the indifference of uranium-238 to neutrons turns out to be disastrous: the process withers before it has time to gain strength. But the more neutron-hungry atoms of the isotope 235 in uranium, the more vigorously the reaction will proceed.

But in order for the process to begin, the first neutron is also needed, that "match" that should cause an atomic "fire". Of course, for this purpose, you can use conventional neutron sources, which scientists have previously used in their research - not very convenient, but possible. Is there a more suitable "match"?

There is. It was found by other Soviet scientists K. A. Petrzhak and G. N. Flerov. Investigating the behavior of uranium in 1939-1940, they came to the conclusion that the nuclei of this element are capable of decaying spontaneously. This was confirmed by the results of experiments carried out by them in one of the Leningrad laboratories. But, perhaps, uranium did not decay by itself, but, for example, under the action of cosmic rays: after all, the Earth is constantly under their shelling. This means that the experiments must be repeated deep underground, where these space guests do not penetrate. After consulting with the leading Soviet atomic scientist I. V. Kurchatov, the young researchers decided to conduct experiments at some station of the Moscow Metro. In the People's Commissariat of Railways, this did not meet with obstacles, and soon equipment weighing about three tons was delivered to the office of the head of the Dynamo metro station, located at a depth of 50 meters, on the shoulders of scientists.

As always, blue trains passed by, thousands of passengers descended and ascended the escalator, and none of them imagined that experiments were being carried out somewhere very close, the significance of which can hardly be overestimated. And finally, results similar to those observed in Leningrad were obtained. There was no doubt: spontaneous decay is inherent in uranium nuclei. To notice it, it was necessary to show outstanding experimental skill: for 1 hour out of every

60,000,000,000,000 uranium atoms only one decays. Truly a drop in the ocean!

K. A. Petrzhak and G. N. Flerov wrote the final page in that part of the biography of uranium that preceded the first chain reaction in the world. It was carried out on December 2, 1942 by Enrico Fermi.

In the late 1930s, Fermi, like many other prominent scientists, fleeing the Nazi plague, was forced to emigrate to America. Here he intended to continue his most important experiments. But this required a lot of money. It was necessary to convince the American government that Fermi's experiments would make it possible to obtain powerful atomic weapons that could be used to fight fascism. This mission was undertaken by the world famous scientist Albert Einstein. He writes a letter to US President Franklin Roosevelt, which begins with the words: “Sir! The latest work of E. Fermi and L. Szilard, which I read in the manuscript, allows us to hope that the element uranium in the near future can be turned into a new important source of energy ... ". In the letter, the scientist urged the government to start funding research on uranium. Given the enormous authority of Einstein and the seriousness of the international situation, Roosevelt gave his consent.

At the end of 1941, Chicagoans could notice an unusual revival that reigned in the territory of one of the stadiums, which had nothing to do with sports. Every now and then trucks loaded with cargo drove up to its gates. Numerous guards did not allow outsiders to even approach the stadium fence. Here, on the tennis courts under the west stand, Enrico Fermi was preparing his most dangerous experiment - the implementation of a controlled chain reaction of fission of uranium nuclei. Work on the construction of the world's first nuclear reactor was carried out day and night throughout the year.

The morning of December 2, 1942 came. All night long, scientists did not close their eyes, again and again checking the calculations. It's no joke to say that the stadium is located in the very center of a multi-million city, and although the calculations convinced that the reaction in the atomic boiler would be slow, that is, it would not be explosive, no one had the right to risk the lives of hundreds of thousands of people. The day had already begun long ago, it was time for breakfast, but everyone forgot about it—they were impatient to start storming the atom as soon as possible. However, Fermi is in no hurry: we need to give tired people a rest, we need a relaxation, in order to carefully weigh and think everything over again. Caution and more caution. And so, when everyone was waiting for the command to start the experiment, Fermi uttered his famous phrase, which went down in the history of the conquest of the atom, just two words: "Let's go have breakfast!"

Breakfast is over, everything is back in place - the experience begins. The views of scientists are riveted to the instruments. Excruciating minutes of waiting. And finally, the neutron counters clicked like machine guns. They seemed to choke on a huge number of neutrons, not having time to count them! The chain reaction has begun! It happened at 3:25 p.m. Chicago time. The atomic fire was allowed to burn for 28 minutes, and then, at Fermi's command, the chain reaction was stopped.

One of the participants in the experiment went to the phone and informed the authorities in a prearranged cipher phrase: “The Italian navigator has reached the New World!” This meant that the eminent Italian scientist Enrico Fermi had released the energy of the atomic nucleus and proved that man could control and use it at will.

But the will is different. In those years when the described events took place, the chain reaction was considered primarily as a stage on the way to the creation of an atomic bomb. It was in this direction that the work of atomic scientists was continued in America.

The situation in the scientific circles associated with these works was extremely tense. But even here it was not without curiosities.

In the autumn of 1943, it was decided to try to take the greatest physicist Niels Bohr out of Germany-occupied Denmark to America in order to use his vast knowledge and talent. On a dark night, on a fishing boat, secretly guarded by British submarines, the scientist disguised as a fisherman was taken to Sweden, from where he was supposed to be transported by plane to England, and only then to the USA.

Bor's entire luggage consisted of one bottle. This ordinary green Danish beer bottle, in which he secretly kept priceless heavy water from the Germans, was kept by the physicist like the apple of his eye: according to many atomic scientists, it was heavy water that could serve as a neutron moderator for a nuclear reaction.

Bohr took the tiring flight very hard and, as soon as he came to his senses, the first thing he did was check whether the bottle of heavy water was intact. And then, to his great chagrin, the scientist discovered that he had become a victim of his own absent-mindedness: in his hands was a bottle with real Danish beer, and a vessel with heavy water was left at home in the refrigerator.

When the first small piece of uranium-235 destined for the atomic bomb was produced at the giant Oak Ridge factories in Tennessee, it was sent by special courier to Los Alamos, hidden among the canyons of New Mexico, where this deadly weapon was created. The courier, who was to drive himself, was not told what was in the box given to him, but he had heard more than once terrible stories about the mysterious "death rays" born in Oak Ridge. The farther he rode, the more excitement seized him. In the end, he decided, at the first suspicious sign in the behavior of the box hidden behind him, to run as fast as he could from the car.

Driving along a long bridge, the driver suddenly heard a loud shot from behind. As if catapulted, he jumped out of the car and ran as fast as he had ever run in his life. But now, having run a fair distance, he stopped in exhaustion, made sure that he was safe and sound, and even ventured to look around. In the meantime, a long tail of impatiently honking cars had already grown behind his car. I had to turn back and keep going.

But as soon as he got behind the wheel, a loud shot rang out again, and the instinct of self-preservation again literally threw the poor fellow out of the car and made him roar from the ill-fated box. Only after an angry policeman caught up with him on a motorcycle and saw government documents, the frightened driver learned that the shots were coming from a nearby training ground, where new artillery shells were being tested at that time.

The work at Los Alamos was carried out in the strictest secrecy. All major scientists were here under false names. So, Niels Bohr, for example, was known in Los Alamos as Nicholas Baker, Enrico Fermi was Henry Farmer, Eugene Wigner was Eugene Wagner.

Once, when Fermi and Wigner were leaving the territory of a secret factory, they were stopped by a sentry. Fermi produced his ID in Farmer's name, but Wigner could not find his papers. The sentry had a list of those who were allowed to enter and exit the factory. "What is your last name?" he asked. The absent-minded professor at first, out of habit, muttered "Wigner", but then he caught himself and corrected himself: "Wagner." This aroused the sentinel's suspicions. Wagner was on the list, but Wigner was not. He turned to Fermi, whom he already knew well by sight, and asked: "Is this man called Wagner?" “His name is Wagner. This is as true as the fact that I am a Farmer, ”Having hidden a smile, Fermi solemnly assured the sentry, and he let the scientists through.

Around the middle of 1945, work on the creation of an atomic bomb, which had spent two billion dollars, was completed, and on August 6, a giant fire mushroom appeared over the Japanese city of Hiroshima, which claimed tens of thousands of lives. This date became a black day in the history of civilization. The greatest achievement of science has given birth to the greatest tragedy of mankind.

Before scientists, before the whole world, the question arose: what next? Continue to improve nuclear weapons, create even more terrible means of exterminating people?

Not! From now on, the colossal energy contained in the nuclei of atoms must serve man. The first step along this path was taken by Soviet scientists under the guidance of Academician IV Kurchatov. On June 27, 1954, Moscow radio broadcast a message of exceptional importance: “At present, in the Soviet Union, the efforts of Soviet scientists and engineers have successfully completed the design and construction of the first industrial nuclear power plant with a useful power of 5,000 kilowatts.” For the first time, a current flowed through the wires that carried energy born in the depths of the uranium atom.

"This historic event," the Daily Worker wrote in those days, "is of immeasurably greater international significance than the dropping of the first atomic bomb on Hiroshima..."

The launch of the first nuclear power plant laid the foundation for the development of a new branch of technology - nuclear energy. Uranium became the peaceful fuel of the 20th century.

Another five years passed, and the world's first nuclear-powered icebreaker "Lenin" left the stocks of Soviet shipyards. To make its engines work at full power (44 thousand horsepower!), You need to "burn" only a few tens of grams of uranium. A small piece of this nuclear fuel is capable of replacing thousands of tons of fuel oil or coal, which are literally forced to drag ordinary motor ships behind them, making, for example, a London-New York voyage. And the Lenin nuclear-powered icebreaker with a reserve of uranium fuel of several tens of kilograms can crush the ice of the Arctic for three years without entering the port for “refuelling”.

In 1974, an even more powerful nuclear icebreaker, the Arktika, "began to fulfill its duties".

Every year the share of nuclear fuel in the world balance of energy resources is becoming more tangible. Nowadays, every fourth light bulb in Russia shines because of nuclear power plants. The advantages of this type of fuel are undeniable. But do not forget about the dangers of radiation. Millions of people have been affected. Among them, more than 100,000 were killed due to the terrible accident at the Chernobol nuclear power plant in 1986. And even now the territory near the Chernobyl nuclear power plant is contaminated and not suitable for living. It will be at least another hundred years before a person can return and live there. But even without accidents, not everything is so smooth. After all, the use of uranium fuel is associated with many difficulties, of which perhaps the most important is the destruction of the resulting radioactive waste. To lower them in special containers to the bottom of the seas and oceans? Bury them deep in the ground? It is unlikely that such methods will completely solve the problem: after all, in the end, deadly substances remain on our planet. Why not try to send them somewhere far away—to other celestial bodies? This idea was put forward by one of the US scientists. He proposed loading the waste from nuclear power plants onto "cargo" spacecraft following the Earth-Sun route. Of course, today such “parcels” would be expensive for senders, but, according to some optimistic experts, in 10 years these transport operations will become quite justified.

Nowadays, it is no longer necessary to have a rich imagination to predict the great future of uranium. Uranus tomorrow is space rockets directed into the depths of the Universe, and giant underwater cities, provided with energy for decades, this is the creation of artificial islands and the flooding of deserts, this is penetration to the very bowels of the Earth and the transformation of the climate of our planet.

Uranium, perhaps the most amazing metal of nature, opens up fabulous prospects for man!

The content of the article

URANUS, U (uranium), a metallic chemical element of the actinide family, which includes Ac, Th, Pa, U, and the transuranium elements (Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr). Uranium has become famous for its use in nuclear weapons and nuclear power. Uranium oxides are also used to color glass and ceramics.

Finding in nature.

The content of uranium in the earth's crust is 0.003%, it occurs in the surface layer of the earth in the form of four types of deposits. Firstly, these are veins of uraninite, or uranium pitch (uranium dioxide UO 2), very rich in uranium, but rare. They are accompanied by deposits of radium, since radium is a direct product of the isotopic decay of uranium. Such veins are found in Zaire, Canada (Great Bear Lake), the Czech Republic and France. The second source of uranium is conglomerates of thorium and uranium ore, together with ores of other important minerals. Conglomerates usually contain sufficient quantities of gold and silver to extract, and uranium and thorium become accompanying elements. Large deposits of these ores are found in Canada, South Africa, Russia and Australia. The third source of uranium is sedimentary rocks and sandstones, rich in the mineral carnotite (potassium uranyl vanadate), which contains, in addition to uranium, a significant amount of vanadium and other elements. Such ores are found in the western states of the United States. Iron-uranium shales and phosphate ores constitute the fourth source of deposits. Rich deposits are found in the shales of Sweden. Some phosphate ores in Morocco and the United States contain significant amounts of uranium, and phosphate deposits in Angola and the Central African Republic are even richer in uranium. Most lignites and some coals usually contain uranium impurities. Uranium-rich lignite deposits have been found in North and South Dakota (USA) and bituminous coals in Spain and the Czech Republic.

Opening.

Uranium was discovered in 1789 by the German chemist M. Klaproth, who named the element in honor of the discovery of the planet Uranus 8 years earlier. (Klaproth was the leading chemist of his time; he also discovered other elements, including Ce, Ti, and Zr.) In fact, the substance obtained by Klaproth was not elemental uranium, but an oxidized form of it, and elemental uranium was first obtained by the French chemist E. .Peligot in 1841. From the moment of discovery until the 20th century. uranium was not as important as it is now, although many physical properties, as well as atomic mass and density were determined. In 1896, A. Becquerel found that uranium salts have radiation that illuminates a photographic plate in the dark. This discovery stimulated chemists to research in the field of radioactivity, and in 1898 the French physicists, the spouses P. Curie and M. Sklodowska-Curie, isolated salts of the radioactive elements polonium and radium, and E. Rutherford, F. Soddy, C. Faience and other scientists developed the theory of radioactive decay, which laid the foundations of modern nuclear chemistry and nuclear energy.

First applications of uranium.

Although the radioactivity of uranium salts was known, its ores in the first third of this century were used only to obtain the accompanying radium, and uranium was considered an undesirable by-product. Its use was concentrated mainly in the technology of ceramics and in metallurgy; Uranium oxides were widely used to color glass in colors from pale yellow to dark green, which contributed to the development of inexpensive glass production. Today, products from these industries are identified as fluorescent under ultraviolet light. During the First World War and shortly thereafter, uranium in the form of carbide was used in the manufacture of tool steels, similarly to Mo and W; 4–8% uranium replaced tungsten, which was limited in production at the time. To obtain tool steels in 1914–1926, several tons of ferrouranium were produced annually, containing up to 30% (mass.) U. However, this use of uranium did not last long.

Modern use of uranium.

The uranium industry began to take shape in 1939, when fission of the uranium isotope 235 U was carried out, which led to the technical implementation of controlled chain reactions of uranium fission in December 1942. This was the birth of the era of the atom, when uranium turned from a minor element into one of the most important elements in life society. The military importance of uranium for the production of the atomic bomb and its use as fuel in nuclear reactors created a demand for uranium that increased astronomically. An interesting chronology of the growth in uranium demand is based on the history of deposits in the Great Bear Lake (Canada). In 1930, resin blende, a mixture of uranium oxides, was discovered in this lake, and in 1932 a technology for purifying radium was established in this area. From each ton of ore (tar blende), 1 g of radium was obtained and about half a ton of a by-product - uranium concentrate. However, radium was scarce and its extraction was stopped. From 1940 to 1942, development was resumed and uranium ore was shipped to the United States. In 1949 a similar purification of uranium, with some modifications, was applied to produce pure UO 2 . This production has grown and is now one of the largest uranium productions.

Properties.

Uranium is one of the heaviest elements found in nature. Pure metal is very dense, ductile, electropositive with low electrical conductivity and highly reactive.

Uranium has three allotropic modifications: a-uranium (orthorhombic crystal lattice), exists in the range from room temperature to 668 ° C; b- uranium (a complex crystal lattice of a tetragonal type), stable in the range of 668–774 ° С; g- uranium (body-centered cubic crystal lattice), stable from 774 ° C up to the melting point (1132 ° C). Since all isotopes of uranium are unstable, all of its compounds exhibit radioactivity.

Isotopes of uranium

238 U, 235 U, 234 U are found in nature in a ratio of 99.3:0.7:0.0058, and 236U in trace amounts. All other isotopes of uranium from 226 U to 242 U are obtained artificially. The isotope 235 U is of particular importance. Under the action of slow (thermal) neutrons, it is divided with the release of enormous energy. Complete fission of 235 U results in the release of a "thermal energy equivalent" of 2h 10 7 kWh/kg. The fission of 235 U can be used not only to produce large amounts of energy, but also to synthesize other important actinide elements. Natural isotopic uranium can be used in nuclear reactors to produce neutrons produced by 235U fission, while excess neutrons not required by the chain reaction can be captured by another natural isotope, resulting in plutonium production:

When bombarded with 238 U by fast neutrons, the following reactions occur:

According to this scheme, the most common isotope 238 U can be converted into plutonium-239, which, like 235 U, is also capable of fission under the influence of slow neutrons.

At present, a large number of artificial isotopes of uranium have been obtained. Among them, 233 U is especially notable in that it also fissions when interacting with slow neutrons.

Some other artificial isotopes of uranium are often used as radioactive labels (tracers) in chemical and physical research; it is first of all b- emitter 237 U and a- emitter 232 U.

Connections.

Uranium, a highly reactive metal, has oxidation states from +3 to +6, is close to beryllium in the activity series, interacts with all non-metals and forms intermetallic compounds with Al, Be, Bi, Co, Cu, Fe, Hg, Mg, Ni, Pb, Sn and Zn. Finely divided uranium is especially reactive, and at temperatures above 500°C it often enters into reactions characteristic of uranium hydride. Lumpy uranium or shavings burn brightly at 700–1000°C, while uranium vapors burn already at 150–250°C; uranium reacts with HF at 200–400°C, forming UF 4 and H 2 . Uranium slowly dissolves in concentrated HF or H 2 SO 4 and 85% H 3 PO 4 even at 90 ° C, but easily reacts with conc. HCl and less active with HBr or HI. The reactions of uranium with dilute and concentrated HNO 3 proceed most actively and rapidly with the formation of uranyl nitrate ( see below). In the presence of HCl, uranium rapidly dissolves in organic acids, forming organic salts U 4+ . Depending on the degree of oxidation, uranium forms several types of salts (the most important among them with U 4+, one of them UCl 4 is an easily oxidized green salt); uranyl salts (UO 2 2+ radical) of the UO 2 (NO 3) 2 type are yellow and fluoresce green. Uranyl salts are formed by dissolving amphoteric oxide UO 3 (yellow color) in an acidic medium. In an alkaline environment, UO 3 forms uranates of the Na 2 UO 4 or Na 2 U 2 O 7 type. The latter compound ("yellow uranyl") is used for the manufacture of porcelain glazes and in the production of fluorescent glasses.

Uranium halides were widely studied in the 1940s–1950s, as they were the basis for the development of methods for separating uranium isotopes for an atomic bomb or a nuclear reactor. Uranium trifluoride UF 3 was obtained by reduction of UF 4 with hydrogen, and uranium tetrafluoride UF 4 is obtained in various ways by reactions of HF with oxides such as UO 3 or U 3 O 8 or by electrolytic reduction of uranyl compounds. Uranium hexafluoride UF 6 is obtained by fluorination of U or UF 4 with elemental fluorine or by the action of oxygen on UF 4 . Hexafluoride forms transparent crystals with a high refractive index at 64°C (1137 mmHg); the compound is volatile (sublimes at 56.54 ° C under normal pressure conditions). Uranium oxohalides, for example, oxofluorides, have the composition UO 2 F 2 (uranyl fluoride), UOF 2 (uranium oxide difluoride).

Uranium is a chemical element of the actinide family with atomic number 92. It is the most important nuclear fuel. Its concentration in the earth's crust is about 2 parts per million. Important uranium minerals include uranium oxide (U 3 O 8), uraninite (UO 2), carnotite (potassium uranyl vanadate), otenite (potassium uranyl phosphate), and torbernite (hydrous copper and uranyl phosphate). These and other uranium ores are sources of nuclear fuel and contain many times more energy than all known recoverable fossil fuel deposits. 1 kg of uranium 92 U gives as much energy as 3 million kg of coal.

Discovery history

The chemical element uranium is a dense, solid silver-white metal. It is ductile, malleable and can be polished. Metal oxidizes in air and ignites when crushed. Relatively poor conductor of electricity. The electronic formula of uranium is 7s2 6d1 5f3.

Although the element was discovered in 1789 by the German chemist Martin Heinrich Klaproth, who named it after the newly discovered planet Uranus, the metal itself was isolated in 1841 by the French chemist Eugène-Melchior Peligot by reduction from uranium tetrachloride (UCl 4 ) with potassium.

Radioactivity

The creation of the periodic table by the Russian chemist Dmitri Mendeleev in 1869 focused attention on uranium as the heaviest known element, which it remained until the discovery of neptunium in 1940. In 1896, the French physicist Henri Becquerel discovered the phenomenon of radioactivity in it. This property was later found in many other substances. It is now known that radioactive uranium in all its isotopes consists of a mixture of 238 U (99.27%, half-life - 4,510,000,000 years), 235 U (0.72%, half-life - 713,000,000 years) and 234 U (0.006%, half-life - 247,000 years). This makes it possible, for example, to determine the age of rocks and minerals in order to study geological processes and the age of the Earth. To do this, they measure the amount of lead, which is the end product of the radioactive decay of uranium. In this case, 238 U is the initial element, and 234 U is one of the products. 235 U gives rise to actinium decay series.

Opening a chain reaction

The chemical element uranium became the subject of wide interest and intensive study after the German chemists Otto Hahn and Fritz Strassmann discovered nuclear fission in it at the end of 1938 when bombarding it with slow neutrons. In early 1939, the American physicist of Italian origin Enrico Fermi suggested that among the products of the fission of the atom there may be elementary particles capable of generating a chain reaction. In 1939, the American physicists Leo Szilard and Herbert Anderson, as well as the French chemist Frederic Joliot-Curie and their colleagues, confirmed this prediction. Subsequent studies have shown that, on average, 2.5 neutrons are released during the fission of an atom. These discoveries led to the first self-sustaining nuclear chain reaction (12/02/1942), the first atomic bomb (07/16/1945), its first use in military operations (08/06/1945), the first nuclear submarine (1955) and the first full-scale nuclear power plant ( 1957).

Oxidation states

The chemical element uranium, being a strong electropositive metal, reacts with water. It dissolves in acids, but not in alkalis. Important oxidation states are +4 (as in UO 2 oxide, tetrahalides such as UCl 4 , and the green water ion U 4+) and +6 (as in UO 3 oxide, UF 6 hexafluoride, and UO 2 2+ uranyl ion). In an aqueous solution, uranium is most stable in the composition of the uranyl ion, which has a linear structure [O = U = O] 2+ . The element also has +3 and +5 states, but they are unstable. Red U 3+ oxidizes slowly in water that does not contain oxygen. The color of the UO 2 + ion is unknown because it undergoes disproportionation (UO 2 + is simultaneously reduced to U 4+ and oxidized to UO 2 2+ ) even in very dilute solutions.

Nuclear fuel

When exposed to slow neutrons, the fission of the uranium atom occurs in the relatively rare isotope 235 U. This is the only natural fissile material, and it must be separated from the isotope 238 U. However, after absorption and negative beta decay, uranium-238 turns into a synthetic element plutonium, which is split by the action of slow neutrons. Therefore, natural uranium can be used in converter and breeder reactors, in which fission is supported by rare 235 U and plutonium is produced simultaneously with the transmutation of 238 U. Fissile 233 U can be synthesized from the thorium-232 isotope, which is widespread in nature, for use as nuclear fuel. Uranium is also important as the primary material from which synthetic transuranium elements are obtained.

Other uses of uranium

Compounds of the chemical element were previously used as dyes for ceramics. Hexafluoride (UF 6) is a solid with an unusually high vapor pressure (0.15 atm = 15,300 Pa) at 25 °C. UF 6 is chemically very reactive, but despite its corrosive nature in the vapor state, UF 6 is widely used in gas diffusion and gas centrifuge methods to obtain enriched uranium.

Organometallic compounds are an interesting and important group of compounds in which metal-carbon bonds connect a metal to organic groups. Uranocene is an organouranium compound U(C 8 H 8) 2 in which the uranium atom is sandwiched between two layers of organic rings bonded to C 8 H 8 cyclooctatetraene. Its discovery in 1968 opened up a new field of organometallic chemistry.

Depleted natural uranium is used as a means of radiation protection, ballast, in armor-piercing projectiles and tank armor.

Recycling

The chemical element, although very dense (19.1 g / cm 3), is a relatively weak, non-flammable substance. Indeed, the metallic properties of uranium seem to place it somewhere between silver and other true metals and non-metals, so it is not used as a structural material. The main value of uranium lies in the radioactive properties of its isotopes and their ability to fission. In nature, almost all (99.27%) of the metal consists of 238 U. The rest is 235 U (0.72%) and 234 U (0.006%). Of these natural isotopes, only 235 U is directly fissioned by neutron irradiation. However, when 238 U is absorbed, it forms 239 U, which eventually decays into 239 Pu, a fissile material of great importance for nuclear energy and nuclear weapons. Another fissile isotope, 233 U, can be produced by neutron irradiation with 232 Th.

crystalline forms

The characteristics of uranium cause it to react with oxygen and nitrogen even under normal conditions. At higher temperatures, it reacts with a wide range of alloying metals to form intermetallic compounds. The formation of solid solutions with other metals is rare due to the special crystal structures formed by the atoms of the element. Between room temperature and a melting point of 1132 °C, uranium metal exists in 3 crystalline forms known as alpha (α), beta (β) and gamma (γ). The transformation from α- to β-state occurs at 668 °C and from β to γ ​​- at 775 °C. γ-uranium has a body-centered cubic crystal structure, while β has a tetragonal one. The α phase consists of layers of atoms in a highly symmetrical orthorhombic structure. This anisotropic distorted structure prevents the alloying metal atoms from replacing the uranium atoms or occupying the space between them in the crystal lattice. It was found that only molybdenum and niobium form solid solutions.

Ores

The Earth's crust contains about 2 parts per million of uranium, which indicates its wide distribution in nature. The oceans are estimated to contain 4.5 x 109 tons of this chemical element. Uranium is an important constituent of over 150 different minerals and a minor constituent of another 50. Primary minerals found in igneous hydrothermal veins and in pegmatites include uraninite and its variety pitchblende. In these ores, the element occurs in the form of dioxide, which, due to oxidation, can vary from UO 2 to UO 2.67. Other economically significant products from uranium mines are autunite (hydrated calcium uranyl phosphate), tobernite (hydrated copper uranyl phosphate), coffinite (black hydrated uranium silicate), and carnotite (hydrated potassium uranyl vanadate).

It is estimated that more than 90% of known low-cost uranium reserves are found in Australia, Kazakhstan, Canada, Russia, South Africa, Niger, Namibia, Brazil, China, Mongolia and Uzbekistan. Large deposits are found in the conglomerate rock formations of Elliot Lake, located north of Lake Huron in Ontario, Canada, and in the South African Witwatersrand gold mine. Sand formations in the Colorado Plateau and in the Wyoming Basin of the western United States also contain significant uranium reserves.

Mining

Uranium ores are found both in near-surface and deep (300-1200 m) deposits. Underground, the seam thickness reaches 30 m. As in the case of ores of other metals, uranium mining at the surface is carried out by large earth-moving equipment, and the development of deep deposits is carried out by traditional methods of vertical and inclined mines. The world production of uranium concentrate in 2013 amounted to 70 thousand tons. The most productive uranium mines are located in Kazakhstan (32% of the total production), Canada, Australia, Niger, Namibia, Uzbekistan and Russia.

Uranium ores usually contain only a small amount of uranium-bearing minerals, and they cannot be smelted by direct pyrometallurgical methods. Instead, hydrometallurgical procedures should be used to extract and purify uranium. Increasing the concentration greatly reduces the load on the processing circuits, but none of the conventional beneficiation methods commonly used for mineral processing, such as gravity, flotation, electrostatic and even hand sorting, are applicable. With few exceptions, these methods result in a significant loss of uranium.

Burning

The hydrometallurgical processing of uranium ores is often preceded by a high-temperature calcination step. Firing dehydrates the clay, removes carbonaceous materials, oxidizes sulfur compounds to harmless sulfates, and oxidizes any other reducing agents that may interfere with subsequent processing.

Leaching

Uranium is extracted from roasted ores with both acidic and alkaline aqueous solutions. For all leaching systems to function successfully, the chemical element must either initially be present in the more stable 6-valent form or be oxidized to this state during processing.

Acid leaching is usually carried out by stirring the mixture of ore and lixiviant for 4-48 hours at ambient temperature. Except in special circumstances, sulfuric acid is used. It is served in quantities sufficient to obtain the final liquor at pH 1.5. Sulfuric acid leaching schemes typically use either manganese dioxide or chlorate to oxidize tetravalent U 4+ to 6-valent uranyl (UO 2 2+). As a rule, about 5 kg of manganese dioxide or 1.5 kg of sodium chlorate per ton is sufficient for the oxidation of U 4+. In any case, oxidized uranium reacts with sulfuric acid to form the 4- uranyl sulfate complex anion.

Ore containing a significant amount of basic minerals such as calcite or dolomite is leached with a 0.5-1 molar sodium carbonate solution. Although various reagents have been studied and tested, the main oxidizing agent for uranium is oxygen. Ores are usually leached in air at atmospheric pressure and at a temperature of 75-80 °C for a period of time that depends on the specific chemical composition. Alkali reacts with uranium to form a readily soluble complex ion 4-.

Before further processing, solutions resulting from acid or carbonate leaching must be clarified. Large-scale separation of clays and other ore slurries is accomplished through the use of effective flocculating agents, including polyacrylamides, guar gum, and animal glue.

Extraction

Complex ions 4- and 4- can be sorbed from their respective leaching solutions of ion exchange resins. These special resins, characterized by their sorption and elution kinetics, particle size, stability and hydraulic properties, can be used in various processing technologies, such as fixed and moving bed, basket type and continuous slurry ion exchange resin method. Usually, solutions of sodium chloride and ammonia or nitrates are used to elute adsorbed uranium.

Uranium can be isolated from acid ore liquors by solvent extraction. In industry, alkyl phosphoric acids, as well as secondary and tertiary alkylamines, are used. As a general rule, solvent extraction is preferred over ion exchange methods for acidic filtrates containing more than 1 g/l uranium. However, this method is not applicable to carbonate leaching.

The uranium is then purified by dissolving in nitric acid to form uranyl nitrate, extracted, crystallized and calcined to form UO 3 trioxide. The reduced UO2 dioxide reacts with hydrogen fluoride to form tetrafluoride UF4, from which metallic uranium is reduced by magnesium or calcium at a temperature of 1300 °C.

Tetrafluoride can be fluorinated at 350 °C to form UF 6 hexafluoride, which is used to separate enriched uranium-235 by gas diffusion, gas centrifugation, or liquid thermal diffusion.

Uranus is one of the heavy metal elements in the periodic table. Uranium is widely used in the energy and military industries. In the periodic table, it can be found at number 92 and is denoted by the Latin letter U with a mass number of 238.

How Uranus Was Discovered

In general, such a chemical element as uranium has been known for a very long time. It is known that even before our era, natural uranium oxide was used to make a yellow glaze for ceramics. The discovery of this element can be considered in 1789, when a German chemist named Martin Heinrich Klaproth recovered a black metal-like material from ore. Martin decided to call this material Uranus in order to support the name of the new discovered planet of the same name (the planet Uranus was discovered in the same year). In 1840, it was revealed that this material, discovered by Klaproth, turned out to be Uranium oxide, despite the characteristic metallic luster. Eugene Melchior Peligot synthesized atomic Uranium from oxide and determined its atomic weight to be 120 AU, and in 1874 Mendeleev doubled this value, placing it in the farthest cell of his table. Only 12 years later, Mendeleev's decision to double the mass was confirmed by the experiments of the German chemist Zimmermann.

Where and how is uranium mined

Uranium is a fairly common element, but it is common in the form of uranium ore. For you to understand, its content in the earth's crust is 0.00027% of the total mass of the Earth. Uranium ore is usually found in acidic mineral rocks with a high silicon content. The main types of uranium ores are pitchblende, carnotite, casolite and samarskite. The largest reserves of uranium ores, taking into account reserve deposits, are such countries as Australia, Russia and Kazakhstan, and of all these, Kazakhstan occupies a leading position. Uranium mining is a very complicated and expensive procedure. Not all countries can afford to mine and synthesize pure uranium. The production technology is as follows: ore or minerals are mined in mines, comparable to gold or precious stones. The extracted rocks are crushed and mixed with water in order to separate the uranium dust from the rest. Uranium dust is very heavy and therefore it precipitates faster than others. The next step is the purification of uranium dust from other rocks by acid or alkaline leaching. The procedure looks something like this: the uranium mixture is heated to 150 ° C and pure oxygen is supplied under pressure. As a result, sulfuric acid is formed, which purifies uranium from other impurities. Well, at the final stage, already pure uranium particles are selected. In addition to uranium dust, there are other useful minerals.

The danger of radioactive radiation from uranium

Everyone is well aware of such a concept as radioactive radiation and the fact that it causes irreparable harm to health, which leads to death. Uranium is just one of these elements, which under certain conditions can release radioactive radiation. In free form, depending on its variety, it can emit alpha and beta rays. Alpha rays do not pose a great danger to humans if the radiation is external, since this radiation has a low penetrating power, but when it enters the body, they cause irreparable harm. Even a sheet of writing paper is enough to contain external alpha rays. With beta radiation, things are more serious, but not by much. The penetrating power of beta radiation is higher than that of alpha radiation, but 3-5 mm of tissue is required to contain beta radiation. How would you say? Uranium is a radioactive element that is used in nuclear weapons! That's right, it is used in nuclear weapons, which cause tremendous damage to all living things. Just when a nuclear warhead is detonated, the main damage to living organisms is caused by gamma radiation and a neutron flux. These types of radiation are formed as a result of a thermonuclear reaction during the explosion of a warhead, which removes uranium particles from a stable state and destroys all life on earth.

Varieties of uranium

As mentioned above, uranium has several varieties. Varieties imply the presence of isotopes, so that you understand isotopes imply the same elements, but with different mass numbers.

So there are two types:

1. Natural;
2. Artificial;

As you may have guessed, natural is the one that is mined from the earth, and artificial people create on their own. Natural isotopes of uranium with a mass number of 238, 235 and 234 are referred to. Moreover, U-234 is a child of U-238, that is, the first is obtained from the decay of the second in natural conditions. The second group of isotopes, which is created artificially, has mass numbers from 217 to 242. Each of the isotopes has different properties and is characterized by different behavior under certain conditions. Depending on the needs, nuclear scientists are trying to find all sorts of solutions to problems, because each isotope has a different energy value.

Half-lives

As mentioned above, each of the isotopes of uranium has a different energy value and different properties, one of which is half-life. In order to understand what it is, you need to start with a definition. The half-life is the time it takes for the number of radioactive atoms to decrease by half. The half-life affects many factors, for example, its energy value or complete cleansing. If we take the latter as an example, then we can calculate for what period of time a complete purification from radioactive contamination of the earth will occur. Half-lives of uranium isotopes:

As can be seen from the table, the half-life of isotopes varies from minutes to hundreds of millions of years. Each of them finds its application in different areas of human life.

The use of uranium is very wide in many areas of activity, but it is of the greatest value in the energy and military spheres. Of greatest interest is the U-235 isotope. Its advantage is that it is able to independently maintain a nuclear chain reaction, which is widely used in the military for the manufacture of nuclear weapons and as fuel in nuclear reactors. In addition, uranium is widely used in geology to determine the age of minerals and rocks, as well as to determine the course of geological processes. In the automotive and aircraft industries, depleted uranium is used as a counterweight and centering element. Also, the use was found in painting, and more specifically as a paint on porcelain and for the manufacture of ceramic glazes and enamels. Another interesting point can be considered the use of depleted uranium to protect against radioactive radiation, as strange as it sounds.

In Bohemia (Czechoslovakia), polymetallic ores have been mined for a long time. Among the ores and minerals, miners often found a heavy black mineral, the so-called resin blende (Pechblende). In the XVIII century. it was believed that this mineral contains zinc and iron, but there was no exact data on its composition. The first study of resin blende was undertaken in 1789 by the German analytical chemist Klaproth. He began by fusing the mineral with caustic potash in a silver crucible; this method Klaproth had developed shortly before, in order to bring silicates and other insoluble substances into solution. However, the fusion product of the mineral was not completely dissolved. From this, Klaproth came to the conclusion that the mineral contains neither molybdenum nor tungsten, but some unknown substance containing a new metal. Klaproth tried to dissolve the mineral in nitric acid and aqua regia. In the remainder of the dissolution, he found silicic acid and a little sulfur, and after a while beautiful light greenish-yellow crystals in the form of hexagonal plates fell out of the solution. Under the action of yellow blood salt, a brown-red precipitate fell out of a solution of these crystals, easily distinguishable from similar precipitates of copper and molybdenum. Klaproth had to work hard before he managed to isolate pure metal. He reduced the oxide with borax, coal and linseed oil, but in all cases a black powder was formed when the mixture was heated. Only as a result of the secondary processing of this powder (heating in a mixture with borax and coal), a sintered mass was obtained with small grains of metal interspersed in it. Klaproth named the new metal uranium (Uranium) in commemoration of the fact that the study of this metal almost coincided in time with the discovery of the planet Uranus (1781). Regarding this name, Klaproth writes: “previously, the existence of only seven planets was recognized, corresponding to the seven metals, which were designated by the signs of the planets. In this regard, it is advisable, following tradition, to name the new metal after the newly discovered planet. The word uranium comes from Greek - sky and thus can mean "heavenly metal". Klaproth renamed pitch blende into "uranium pitch". Pure metallic uranium was first obtained by Peligot in 1840. For a long time, uranium salts were available to chemists in very small quantities; they were used to obtain paints and in photographs Uranium research, although carried out, added little to what Klaproth had established.The atomic weight of uranium was assumed to be 120 until Mendeleev proposed doubling this value. After 1896, when Becquerel discovered the phenomenon of radioactivity, uranium aroused the deepest interest of both chemists and physicists. Becquerel discovered that the double salt potassium uranyl sulfate has an effect on a photographic plate wrapped in black paper, that is, it emits some kind of rays. The Curies, and then other scientists, continued Becquerel's research, as a result of which radioactive elements (radium, polonium and actinium) and many radioactive isotopes of heavy elements were discovered. In 1900, Crookes discovered the first isotope of uranium, uranium-X, and then other isotopes named uranium-I and uranium-II were discovered. In 1913, Fajans and Goering showed that as a result of beta radiation, uranium-X 1 turns into a new element (isotope), which they called breve; later it was called uranium-X 2 . To our time, all members of the uranium-radium series of radioactive decay have been discovered.