Presentation on the topic "discovery of radioactivity." Discovery of radioactivity

Popov Sergey

Radioactivity. Discovery of new radioactive elements.

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Discovery of radioactivity. Discovery of new radioactive chemical elements

Antoine Henri Becquerel French physicist, Nobel Prize winner in physics and one of the discoverers of radioactivity. He studied the connection between luminescence and x-rays, discovered by Henri Poincaré.

Becquerel came up with an idea: isn’t all luminescence accompanied by X-rays? To test his guess, he took several compounds, including one of the uranium salts, which phosphorescent with yellow-green light. Having illuminated it with sunlight, he wrapped the salt in black paper and placed it in a dark closet on a photographic plate, also wrapped in black paper. After some time, developing the plate, Becquerel actually saw the image of a piece of salt. But luminescent radiation could not pass through black paper, and only X-rays could illuminate the plate under these conditions. Becquerel repeated the experiment several times and with equal success. At the end of February 1896, at a meeting of the French Academy of Sciences, he made a report on the X-ray emission of phosphorescent substances. Radioactivity was discovered by him in 1896

After some time, in Becquerel’s laboratory, a plate was accidentally developed on which lay a uranium salt that had not been irradiated by sunlight. Naturally, it did not phosphorescent, but there was an imprint on the plate. Then Becquerel began testing various uranium compounds and minerals (including those that did not exhibit phosphorescence), as well as metallic uranium. The record was invariably overexposed. By placing a metal cross between the salt and the plate, Becquerel obtained faint outlines of the cross on the plate. Then it became clear that new rays had been discovered that passed through opaque objects, but were not x-rays. Becquerel established that the intensity of radiation is determined only by the amount of uranium in the preparation and is completely independent of what compounds it is included in. Thus, this property was inherent not in the compounds, but in the chemical element uranium.

Maria Sklodowska-Curie is a Polish experimental scientist (physicist, chemist), teacher, public figure. Twice Nobel laureate: in physics (1903) and in chemistry (1911), the first twice Nobel laureate in history. Becquerel shares his discovery with the scientists with whom he collaborated - Marie Curie and Pierre Curie. Pierre Curie - French physicist, one of the first researchers of radioactivity, member of the French Academy of Sciences, winner of the Nobel Prize in Physics for 1903.

In her experiments, M. Curie used the ability of radioactive substances to ionize air as a sign of radioactivity. This sign is much more sensitive than the ability of radioactive substances to act on a photographic plate. Measurement of ionization current: 1 - body of the ionization chamber, 2 - electrode separated from 1 by an insulating plug 3.4 - drug under study, 5 - electrometer. Resistance R=108-1012 Ohm. At a sufficiently high battery voltage, all the ions formed in the volume of the chamber by ionizing radiation are collected on the electrodes, and a current proportional to the ionizing effect of the drug flows through the chamber. In the absence of ionizing agents, the air in the chamber is a non-conductor, and the current is zero.

They found that all uranium compounds, and most importantly uranium itself, have the property of natural radioactivity. Becquerel returned to the phosphors that interested him. True, he made another major discovery related to radioactivity. Once, for a public lecture, Becquerel needed a radioactive substance, he took it from the Curies and put the test tube in his vest pocket. After giving a lecture, he returned the radioactive drug to the owners, and the next day he discovered redness of the skin in the shape of a test tube on his body under his vest pocket. Becquerel told Pierre Curie about this, and he experimented on himself: he wore a test tube of radium tied to his forearm for ten hours. A few days later he also developed redness, which then turned into a severe ulcer, from which he suffered for two months. This was the first time the biological effects of radioactivity were discovered.

In 1898 they discovered the radioactivity of thorium, and later they discovered radioactive elements: POLONIUM RADIUM

Applications Currently, radium is sometimes used in compact neutron sources, for this purpose small amounts of it are fused with beryllium. Under the influence of alpha radiation (helium-4 nuclei), neutrons are knocked out of beryllium: 9Be + 4He → 12C + 1n. 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 irradiation in the treatment of malignant diseases of the skin, nasal mucosa, and genitourinary tract. Polonium-210 in alloys with beryllium and boron is used to manufacture compact and very powerful neutron sources that practically do not create γ-radiation. An important area of ​​application for polonium is its use in the form of alloys with lead, yttrium, or independently for the production of powerful and very compact heat sources for autonomous installations, such as space. In addition, polonium is suitable for creating compact “dirty bombs” and is convenient for covert transportation, since it practically does not emit gamma radiation. Therefore, polonium is a strategic metal, must be taken into account very strictly, and its storage must be under state control due to the threat of nuclear terrorism.

Thanks to the discovery of the radioactive decay of elements, the creation of electronic theory and a new model of the atom, the essence and significance of Mendeleev's periodic law appeared in a new light. It was found that the serial (atomic) number of an element in the periodic table (it is designated “Z”) has a real physical and chemical meaning: it corresponds to the total number of electrons in the layers of the shell of a neutral atom of the element and the positive charge of the nucleus of the atom. In 1913-1914 English physicist G.G. J. Moseley (1887-1915) discovered a direct relationship between the X-ray spectrum of an element and its ordinal number. By 1917, through the efforts of scientists from different countries, 24 new chemical elements were discovered, namely: gallium (Ga), scandium (Sc), germanium (Ge), fluorine (F); lanthanides: ytterbium (Yb), holmium (Ho), thulium (Ti), samarium (Stn), gadolinium (Gd), praseodymium (Pr), dysprosium (Dy), neodymium (Nd), europium (Eu) and lutetium (Lu ); inert gases: helium (He), neon (Ne), argon (Ar), krypton (Kg), xenon (Xe) and radon (Rn) and radioactive elements (which included radon): radium (Ra), polonium ( Po), actinium (Ac) and protactinium (Pa). The number of chemical elements in Mendeleev's periodic table increased from 63 in 1869 to 87 in 1917.

A radioactive element is a chemical element all of whose isotopes are radioactive. In practice, this term is often used to describe any element whose natural mixture contains at least one radioactive isotope, that is, if the element exhibits radioactivity in nature. In addition, all isotopes of any of the artificial elements synthesized to date are radioactive.

A radioactive chemical element, under normal conditions - unstable dark blue crystals. Astatine was first obtained artificially in 1940 by D. Corson, K. R. Mackenzie and E. Segre. In 1943-1946, astatine isotopes were discovered as part of natural radioactive series. Astatine is the rarest element found in nature. Basically, its isotopes are obtained by irradiating metallic bismuth or thorium with high-energy α-particles, followed by separation of astatine by coprecipitation, extraction, chromatography or distillation. 211At is very promising for the treatment of thyroid diseases. There is information that the radiobiological effect of astatine α-particles on the thyroid gland is 2.8 times stronger than iodine-131 β-particles. It should be taken into account that with the help of thiocyanate ion it is possible to reliably remove astatine from the body At - A stat

Radioactive transition metal of silver-gray color. The lightest element that has no stable isotopes. The first of the synthesized chemical elements. With the development of nuclear physics, it became clear why technetium cannot be detected in nature: in accordance with the Mattauch-Shchukarev rule, this element does not have stable isotopes. Technetium was synthesized from a molybdenum target irradiated at an accelerator-cyclotron with deuterium nuclei on July 13, 1937 by C. Perrier and E. Segre at the National Laboratory. Lawrence Berkeley in the USA, and then was isolated in its pure form chemically in Palermo in Italy. Widely used in nuclear medicine for studies of the brain, heart, thyroid gland, lungs, liver, gallbladder, kidneys, skeletal bones, blood, as well as for the diagnosis of tumors, also salts of technical acid HTcO4 are the most effective corrosion inhibitor for iron and steel. Tc - Technetium

A heavy, brittle radioactive metal of a silvery-white color. In the periodic table it is located in the actinide family. Plutonium has seven allotropes at certain temperatures and pressure ranges. Both enriched and natural uranium are used to produce plutonium. Widely used in the production of nuclear weapons, fuel for civil and research nuclear reactors, and as a source of energy for spacecraft. The second artificial element after neptunium, obtained in microgram quantities at the end of 1940 in the form of the isotope 238Pu. The first artificial chemical element, the production of which began on an industrial scale (in the USSR, since 1946, several enterprises for the production of weapons-grade uranium and plutonium were created in Chelyabinsk-40). The world's first nuclear bomb, created and tested in 1945 in the United States, used a plutonium charge. Both enriched and natural uranium are used to produce plutonium. The total amount of plutonium stored in the world in all possible forms was estimated in 2003 at 1239 tons. In 2010, this figure increased to ~2000 tons. Pu - Plutonium

Ununtrium (lat. Ununtrium, Uut) or eka-thallium is the 113th chemical element of group III of the periodic system, atomic number 113, atomic mass, the most stable isotope 286Uut. Radioactive. In September 2004, a group from Japan announced the synthesis of the one-atom isotope of element 113, 278Uut. They used the fusion reaction of zinc and bismuth nuclei. As a result, over 8 years, Japanese scientists managed to register 3 events of the birth of ununtria atoms: July 23, 2004, April 2, 2005 and August 12, 2012. Two atoms of another isotope - 282Uut - were synthesized at JINR in 2007 in the reaction 237Np + 48Ca → 282Uut + 3 1 n. Two more isotopes - 285Uut and 286Uut were synthesized at JINR in 2010 as products of two successive α-decays of ununseptium. Uut – Ununtriy

Links to sources of information and images: http:// www.h2o.u-sonic.ru/table/tc.htm http://www.physel.ru/2-mainmenu-73/inmenu-75/721-s- 211-. html http:// www.xumuk.ru/bse/2279.html http:// www.bibliotekar.ru/istoria-tehniki/16.htm http://ru.wikipedia.org/wiki/% D0%9F% D0%BB%D1%83%D1%82%D0%BE%D0%BD%D0%B8%D0%B9 http://ru.wikipedia.org/wiki/%D0%A0%D0%B0%D0% B4%D0%B8%D0%BE%D0%B0%D0%BA%D1%82%D0%B8%D0%B2%D0%BD%D1%8B%D0%B9_% D1%8D%D0%BB% D0%B5%D0%BC%D0%B5%D0%BD%D1%82 http://ru.wikipedia.org/wiki/% D0%A2%D0%B5%D1%85%D0%BD%D0% B5%D1%86%D0%B8%D0%B9 http://ru.wikipedia.org/wiki/% D0%9D%D0%B5%D0%BF%D1%82%D1%83%D0%BD% D0%B8%D0%B9 http://ru.wikipedia.org/wiki/% D0%A3%D0%BD%D1%83%D0%BD%D1%82%D1%80%D0%B8%D0% B9 http://ru.wikipedia.org/wiki/%D0%A0%D0%B0%D0%B4%D0%B8%D0%BE%D0%B0%D0%BA%D1%82%D0%B8% D0%B2%D0%BD%D1%8B%D0%B9_% D1%80%D0%B0%D1%81%D0%BF%D0%B0%D0%B4

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Radioactive radiation Radioactivity has appeared on earth since its formation, and man throughout the history of the development of his civilization has been under the influence of natural sources of radiation. The Earth is exposed to background radiation, the sources of which are radiation from the Sun, cosmic radiation, and radiation from radioactive elements lying in the Earth.

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Discovery The phenomenon of radioactivity was discovered by the French physicist A. Becquerel on March 1, 1896 under random circumstances. Becquerel placed several photographic plates in his desk drawer and, to prevent visible light from reaching them, he pressed them down with a piece of uranium salt. After development and examination, he noticed a blackening of the plate, explaining this by the radiation of invisible rays from the uranium salt. Becquerel moved from uranium salts to pure uranium metal and noted that the effect of emitting rays intensified. Becquerel's experience

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Discovery A piece of uranium salt, without prior illumination, emitted invisible rays that acted on a photographic plate through an opaque screen. Becquerel immediately carried out repeated experiments. It turned out that uranium salts themselves, without any external influence, emit invisible rays that illuminate the photographic plate and pass through opaque layers. On March 2, 1896, Becquerel announced his discovery. An image of a Becquerel photographic plate that was illuminated by radiation from uranium salts. The shadow of a metal Maltese cross placed between the plate and the uranium salt is clearly visible.

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Discovery of new radioactive elements Marie Skłodowska-Curie discovered emissions from thorium. Later, she and her husband discovered previously unknown elements: polonium, radium. Subsequently, it was found that all chemical elements with a serial number greater than 83 are radioactive. Marie Skłodowska-Curie and Pierre Curie
  • The ancient Greek philosopher Democritus suggested that bodies consist of tiny particles - atoms (in translation indivisible).
  • By the end of the 19th century. Experimental facts appeared proving that the atom has a complex structure.

Experimental facts proving the complex structure of the atom

  • Electrification of bodies
  • Current in metals
  • Electrolysis phenomenon
  • Ioffe-Millikan experiments

Discovery of radioactivity

in 1896 by A. Becquerel.

  • Uranus spontaneously emits invisible rays

Properties of rays

  • Ionize the air
  • The electroscope is being opened up
  • Does not depend on what compounds uranium is included in

83 – radioactive " width="640"

Research continued by Marie and Pierre Curie

  • thorium 1898,
  • polonium,
  • radium (radiant)

z 83 – radioactive


  • - emission of various particles by the nuclei of some elements: α -particles; electrons; γ -quanta (α , β , γ -radiation).
  • - the ability of atoms of some radioactive elements to spontaneously emit

Composition of radioactive radiation

1899 E. Rutherford

In a magnetic field, a beam of radioactive radiation was divided into three components:

  • Positively charged - α -particles
  • Negatively charged - β - particles
  • Neutral component of radiation – γ -radiation

All radiations have different penetrating powers

Delayed

  • Sheet of paper 0.1 mm – α -particles
  • Aluminum 5 mm – α -particles, β - particles
  • Lead 1 cm – α -particles, β - particles, γ -radiation

Nature α -particles

  • Helium atomic nuclei
  • m = 4 amu
  • q = 2 e
  • V = 10000-20000 km/s

Nature β -particles

  • Electrons
  • V = 0.99s
  • c – speed of light

Nature γ - radiation

  • Electromagnetic waves (photons)
  • λ = 10 - 10 m
  • Ionize the air
  • Act on photographic plate
  • Not deflected by magnetic field


INTERESTING!

Mushrooms are accumulators of radioactive elements, in particular cesium. All types of mushrooms studied can be divided into four groups: - weakly accumulating - autumn honey fungus; - medium accumulating - porcini mushroom, chanterelle, boletus; - highly accumulating - black milk mushroom, russula, green mushroom; - radionuclide batteries - oiler, Polish mushroom.


UNFORTUNATELY!

  • The lives of both generations of scientists—physicists Curie—were literally sacrificed to her science. Marie Curie, her daughter Irene and son-in-law Frédéric Joliot-Curie died of radiation sickness resulting from years of work with radioactive substances.
  • Here is what M.P. Shaskolskaya writes: “In those distant years, at the dawn of the atomic age, the discoverers of radium did not know about the effects of radiation. Radioactive dust swirled around their laboratory. The experimenters themselves calmly took the drugs with their hands and kept them in their pockets, unaware of the mortal danger. A piece of paper from Pierre Curie's notebook is brought to the Geiger counter (55 years after the notes were made in the notebook!), and a steady hum gives way to noise, almost a roar. The leaf radiates, the leaf seems to breathe radioactivity...”

Radioactive decay

  • - radioactive transformation of nuclei that occurs spontaneously.

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FROM THE HISTORY OF THE DISCOVERY OF RADIOACTIVITY Physics teacher of the Gubinskaya Secondary School Konstantinova Elena Ivanovna "The History of the Discovery of Radioactivity"

  • Table of contents.
  • Introduction………………………………………………………3
  • Chapter first....………………………………………………. 5
  • Chapter two……………………………………………………………… 8
  • Chapter Three…………………………………………………………... 11
  • Chapter Four……………………………………………………………..... 19
  • Conclusion..………………………………………………………………..... 21
  • References…………… ………………………….. 22
  • Appendix one…….…………………………….……... 23
This lesson is dedicated to the history of the discovery of radioactivity, that is, the role of such scientists as the German physicist, Nobel Prize winner Wilhelm Conrad Roentgen, A. Becquerel, the spouses Marie and Pierre Curie, Joliot Curie, in the development of this science. The purpose of the lesson is to consider the formation, fundamental principles of such sciences as radiology, nuclear physics, dosimetry, and to determine the role of certain scientists in the discovery of this wonderful phenomenon. To achieve this goal, the author set himself the following tasks: To consider the activities of Wilhelm Roentgen as a scientist who directed other researchers in this area. Follow the initial discovery of the phenomenon by A. Becquerel. Assess the enormous contribution of the Curie spouses to the accumulation and systematization of knowledge about radioactivity. Analyze the discovery of Joliot Curie Discovery of X-rays It was December 1895. VC. Roentgen, working in a laboratory with a discharge tube, near which there was a fluorescent screen coated with platinum-synoxide barium, observed the glow of this screen. Having covered the tube with a black case, about to finish the experiment, Roentgen again discovered the glow of the screen during the discharge. “Fluorescence” is visible, Roentgen wrote in his first message on December 28, 1895, when the darkness is sufficient and does not depend on whether the paper is presented with the side coated or not coated with platinum-barium syneride. Fluorescence is noticeable even at a distance of two meters from the tube.” X-ray could, however, detect neither reflection nor refraction of X-rays. However, he found that if correct reflection “does not take place, various substances still behave in relation to X-rays in the same way as turbid media in relation to light.” Roentgen established the important fact of scattering of X-rays by matter. However, all his attempts to detect X-ray interference yielded negative results. Attempts to deflect the rays using a magnetic field also yielded negative results. From this, Roentgen concluded that X-rays are not identical with cathode rays, but are excited by them in the glass walls of the discharge tube. At the conclusion of his message, Roentgen discusses the question of the possible nature of the rays he discovered: Roentgen had good reasons to doubt the common nature of light and x-rays, and the correct solution to the question fell to the physics of the 20th century. However, Roentgen's unsuccessful hypothesis was also evidence of the shortcomings of his theoretical thinking, which was prone to one-sided empiricism. A subtle and skillful experimenter, Roentgen had no inclination to search for something new, no matter how paradoxical this may sound in relation to the author of one of the largest new discoveries in the life of physics. Roentgen's discovery of X-rays played an important role in the study of radioactivity. Thanks to him, after repeating the above experiments, thousands of scientists around the world began to explore this area. It is no coincidence that Joliot Curie would later say: “If there had not been Wilhelm Roentgen, I probably would not have existed...” Becquerel's experiments. In 1896, A. Becquerel discovered radioactivity. This discovery was directly related to the discovery of X-ray rays. Becquerel, closely familiar with his father's research on luminescence, drew attention to the fact that the cathode rays in Roentgen's experiments produced both luminescence of the glass and invisible X-rays upon impact. This led him to the idea that all luminescence is accompanied by the simultaneous emission of X-rays. To test this idea, Becquerel used a large number of luminescent materials until, after a series of unsuccessful experiments, he placed two crystalline plates of uranium salt on a photographic plate wrapped in black paper. The uranium salt was exposed to strong sunlight and after several hours of exposure the outline of crystals was clearly visible on the photographic plate. The idea turned out to be confirmed; sunlight excited both the luminescence of the uranium salt and the penetrating radiation acting through the paper on the photographic plate. However, chance intervened. Having again prepared a plate with a crystal of uranium salt, Becquerel again took it out into the sun. The day was cloudy, and the experiment had to be interrupted after a short exposure. In the following days the sun did not appear, and Becquerel decided to develop the plate, without, of course, hoping to get a good picture. But, to his surprise, the picture turned out sharply defined. As a first-class researcher, Becquerel did not hesitate to subject his theory to a serious test and began to study the effect of uranium salts on a plate in the dark. Thus it was discovered - and Becquerel proved this by successive experiments - that uranium and its compound continuously emit without weakening rays that act on a photographic plate and, as Becquerel showed, are also capable of discharging an electroscope, that is, creating ionization. This discovery caused a sensation. So, 1896 was marked by a remarkable event: finally, after several years of searching, radioactivity was discovered. This merit belongs to the great scientist Becquerel. His discovery gave impetus to the development and improvement of this science. Research by the Curies. Pierre Curie's young wife, Maria Sklodowska-Curie, decided to choose the topic of her doctoral dissertation to study a new phenomenon. Her study of the radioactivity of uranium compounds led her to the conclusion that radioactivity is a property belonging to uranium atoms, regardless of whether they are part of a chemical compound or not. At the same time, she “measured the intensity of uranium rays, taking advantage of their property of imparting electrical conductivity to the air.” With this ionization method, she became convinced of the atomic nature of the phenomenon. But even this modest result showed Curie that radioactivity, despite its extraordinary nature, cannot be a property of only one element. “From this time on, it became necessary to find a new term to define a new property of matter, manifested by the elements uranium and thorium. I proposed the name “radioactivity” for this, which became generally accepted.” Curie's attention was drawn to the abnormally high values ​​of radioactivity of some ores. To find out what was wrong, Curie prepared an artificial chalcolithic material from pure substances. This artificial chalcolite, consisting of uranyl nitrate and a solution of copper phosphate in phosphoric acid, after crystallization had “completely normal activity corresponding to its composition: it is 2.5 times less than the activity of uranium.” The truly titanic work of the Curies began, paving the way for humanity to master atomic energy. The new method of chemical analysis developed by Curie played a huge role in the history of atomic physics, making it possible to detect the tiniest masses of radioactive matter

Curie didn't even have

fume hoods. As for the employees, at first they had to work alone. In 1898, in their work on the discovery of radium, they were provided with temporary assistance by a teacher at the industrial school of physics and chemistry, J. Bemont; later they attracted the young chemist A. Debierne, who discovered sea anemone; then they were helped by physicists J. Sagnac and several young physicists. Intense heroic work began to bring results of radioactivity.

In a report to Congress, the Curies described the above history of obtaining new radioactive substances, pointing out that “we call substances emitting Becquerel rays radioactive.” Then they outlined the Curie method of measurement and established that “radioactivity is a phenomenon that can be measured quite accurately,” and the obtained figures for the activity of uranium compounds made it possible to hypothesize the existence of very active substances, which, when tested, led to the discovery of polonium, radium and actinium. The report contained a description of the properties of new elements, the spectrum of radium, an approximate estimate of its atomic mass, and the effects of radioactive radiation. As for the nature of the radioactive rays themselves, for its study the effect of the magnetic field on the rays and the penetrating ability of the rays were studied. P. Curie showed that radium radiation consists of two groups of rays: those deflected by a magnetic field and those not deflected by a magnetic field. Studying deflected rays, the Curies in 1900 became convinced that “the deflected rays β are charged with negative electricity.” It can be accepted that radium also sends negatively charged particles into space.” It was necessary to investigate more closely the nature of these particles. The first definitions of e/m of radium particles belonged to A. Becquerel (1900). “Mr. Becquerel’s experiments gave the first indication on this issue. For e/m an approximate value of 107 absolute electromagnetic units was obtained, for υ value of 1.6 1010 cm per second. The order of these numbers is the same as for cathode rays." “Precise studies on this issue belong to Mr. Kaufman (1901, 1902, 1903)... From Mr. Kaufman’s experiments it follows that for radium rays, the speed of which is significantly greater than the speed of cathode rays, the ratio e/m decreases with increasing speed. In accordance with the work of J. J. Thomson and Townsend, we must assume that the moving particle representing the beam has a charge equal to that carried by the hydrogen atom in electrolysis. This charge is the same for all rays. On this basis, it should be concluded that the greater the mass of particles, the greater their speed.” The deflection of α-rays in a magnetic field was obtained by Rutherford in 1903. Rutherford also owned the names: -α, -β and –γ rays. "1. α (alpha) rays have very low penetrating power; they apparently constitute the main part of the radiation. They are characterized by absorption by matter. The magnetic field affects them very weakly, so they were initially considered insensitive to its action. However, in a strong magnetic field, rays a are slightly deflected, the deflection occurs in a similar way as for cathode rays, only in the opposite sense...” 2. Beta (beta) rays are generally slightly absorbed compared to the previous ones. In a magnetic field they are deflected in the same way and in the same sense as cathode rays. 3. γ (gamma) rays have high penetrating power; the magnetic field does not affect them; they are similar to X-rays.” P. Curie was the first person to experience the destructive effects of nuclear radiation. He was also the first to prove the existence of nuclear energy and measure its amount released during radioactive decay. In 1903, he, together with Laborde, found that “radium salts are a source of heat released continuously and spontaneously” Pierre Curie was well aware of the enormous social consequences of his discovery. In the same year, in his Nobel speech, he said the following prophetic words, which M. Curie put as an epigraph to her book about him: “It is not difficult to foresee that in criminal hands radium can become extremely dangerous, and the question arises whether it is really useful for humanity to know the secrets of nature, whether he is really mature enough to use them correctly, or whether this knowledge will only bring him harm. Experiments of Messrs. The Curies led, first of all, to the discovery of a new radiating metal, similar in its chemical properties to bismuth - a metal that Mr. Curie named polonium in honor of the homeland of his wife (Curie's wife was Polish, née Skłodowska); that their further experiments led to the discovery of a second, highly radiating new metal - radium, which is very similar in chemical properties to barium; that Debierne's experiments led to the discovery of a third radiating new metal - actinium, similar to thorium. Next, Mr. Curie proceeded to the most interesting part of his report - experiments with radium. The above experiments culminated in a demonstration of the luminosity of radium. A glass tube, as thick as a pencil and as long as a little finger, filled to two-thirds with a mixture of radium and barium chloride, emits such strong light for two years that one can read freely near it. The last words sound very naive and indicate very little familiarity with radioactivity at the beginning of the 20th century. However, this poor knowledge of radioactive phenomena did not prevent the emergence and development of a new industry: the radium industry. This industry was the beginning of the future nuclear industry. . The role of the Curies in the history of the discovery of radioactivity is enormous. They not only did a titanic job of studying the radioactive properties of all minerals known at that time, but also made the first attempt at systematization, giving presentations at the Sorbonne University. Discovery of artificial radioactivity. However, it was only one of four great discoveries made in 1932, thanks to which it was called the miracle year of radioactivity. Firstly, in addition to the implementation of artificial transmutation, a positively charged electron, or positron, in contrast, the negative electron has since been called the negatron. Secondly, it was opened neutron- an uncharged elementary particle with a mass of 1 (unit), which can be considered as a neutral nucleus, only without an external electron. Finally, an isotope of hydrogen with mass 2 was discovered, called heavy hydrogen, or deuterium, whose nucleus is thought to consist of a proton R and neutron P; Like ordinary hydrogen, its atom has one outer electron. The next year, 1933, there was another discovery, which in some ways (at least in the opinion of the first researchers of atomic energy) was of the greatest interest. We are talking about the discovery of artificial radioactivity. 1933-1934 For one of the first researchers of this problem - M. Curie - this discovery was of particular interest: it was made by her daughter and son-in-law. M. Curie had the good fortune to pass on the torch she lit to members of her family a few months before her death. The object she had transformed from curiosity to colossus was, a quarter of a century later, on the verge of taking on a new, fruitful life. While studying the mentioned effect of Bothe and Becker, the Joliots discovered that the counter continued to register impulses even after the polonium that originally excited them was removed. These pulses terminated in exactly the same way as the pulses of an unstable radio element with a half-life of 3 min. Scientists found that the aluminum window through which polonium α-radiation passed became radioactive itself due to the neutrons generated; a similar effect occurred for boron and magnesium, only different half-lives were observed (11 and 2.5, respectively min). The reactions for aluminum and boron were as follows: 2713A1(α,n) 3015P*→3014Si+e+; 105B(α,n) 137N* →136C+e+, where the asterisks indicate that the nuclei obtained first are radioactive and undergo secondary transformations indicated by arrows, as a result of which the well-known stable isotopes of silicon and carbon are formed. As for magnesium, all three of its isotopes (with mass numbers 24, 25 and 26) participate in this reaction, generating neutrons, protons, positrons and electrons; as a result, well-known stable isotopes of aluminum and silicon are formed (the transformations are of a combined nature); 2412Мg(α, n)2714Si*→2713Al+е+; 2512Мg(α, р)2813Аl*→2814Si+e-; 2612Мg(α, p)2913Аl*→2914Si+e-. Moreover, using conventional chemical methods used in radiochemistry, it was possible to identify unstable radioactive phosphorus and nitrogen quite easily. These initial results demonstrated the richness of possibilities offered by the newly acquired data. Radioactivity today There are few discoveries in the memory of mankind that would change its fate so dramatically as the discovery of radioactive elements. For more than two thousand years, the atom was represented as a dense, tiny indivisible particle, and suddenly at the dawn of the 20th century it was discovered that atoms are capable of dividing into parts, disintegrating, disappearing, turning into each other. It turned out that the eternal dream of alchemists - the transformation of some elements into others - is realized in nature by itself. This discovery is so significant in its significance that our 20th century began to be called the “atomic age,” the era of the atom, the beginning of the atomic era. It is difficult to name now an area of ​​science or technology that has not been influenced by the discovery of the phenomenon of radioactivity. It revealed the complex internal structure of the atom, and this led to a revision of fundamental ideas about the world around us, to a breakdown of the established, classical picture of the world. Quantum mechanics was created specifically to explain the phenomena that occur inside an atom. This, in turn, caused a revision and development of the mathematical apparatus of physics, changed the face of physics itself, chemistry and a number of other sciences. Literature 1). A.I. Abramov. Measuring the “immeasurable.” Moscow, Atomizdat. 1977. 2). K.A. Gladkov. Atom from A to Z. Moscow, Atomizdat. 1974. 3). E. Curie. Marie Curie. Moscow, Atomizdat. 1976. 4). K.N. Mukhin. Entertaining nuclear physics. Moscow, Atomizdat. 1969. 5). M. Namias. Nuclear power. Moscow, Atomizdat. 1955. 6). N.D. Pilchikov. Radium and radioactivity (collection “Advances in Physics”). Saint Petersburg. 1910. 7). VC. X-ray. About a new kind of rays. Moscow, "Enlightenment". 1933. 8). M. Sklodowska-Curie. Radium and radioactivity. Moscow. 1905. 9). M. Sklodowska-Curie. Pierre Curie. Moscow, "Enlightenment". 1924. 10). F. Soddy. History of atomic energy. Moscow, Atomizdat 1979. 11). A.B. Shalinets, G.N. Fadeev. Radioactive elements. Moscow, "Enlightenment". 1981.