Who discovered radioactive radiation. Discovery of natural radioactivity. Natural radioactive elements

There are several definitions of this remarkable phenomenon, one of which gives such a formulation: “Radioactivity is the spontaneous (spontaneous) transformation of an unstable isotope of a chemical element into another isotope (usually an isotope of another element); in this case, electrons, protons, neutrons or helium nuclei (ά-particles) are emitted. The essence of the discovered phenomenon was a spontaneous change in the composition of the atomic nucleus, which is in the ground state or in an excited long-lived state.

In 1898, other French scientists Maria Sklodowska-Curie and Pierre Curie isolated two new substances from the uranium mineral, radioactive to a much greater extent than uranium and thorium. Thus, two previously unknown radioactive elements were discovered - polonium and radium, and Maria, in addition, discovers (regardless of the German physicist G. Schmidt) the phenomenon of radioactivity in thorium. By the way, she was the first to propose the term radioactivity . Scientists came to the conclusion that radioactivity is a spontaneous process that occurs in the atoms of radioactive elements. Now this phenomenon is defined as a spontaneous transformation of an unstable isotope of one chemical element into an isotope of another element, and in this case, electrons, protons, neutrons or helium nuclei α-particles are emitted. It should be noted here that among the elements contained in the earth's crust, all with serial numbers over 83 are radioactive, i.e. located in the periodic table after bismuth. For 10 years of joint work, they have done a lot to study the phenomenon of radioactivity. It was selfless work in the name of science - in a poorly equipped laboratory and in the absence of the necessary funds. Pierre established the spontaneous release of heat by radium salts. Researchers received this preparation of radium in 1902 in the amount of 0.1 g. To do this, they took 45 months of hard work there and more than 10,000 chemical liberation and crystallization operations. In 1903, the Nobel Prize in Physics was awarded to the Curies and A. Beckerey for their discovery in the field of radioactivity. In total, more than 10 Nobel Prizes in physics and chemistry were awarded for work related to the study and use of radioactivity (A. Beckerey, P. and M. Curie, E. Fermi, E. Rutherford, F. and I. Joliot-Curie, D.Havishi, O.Ganu, E.McMillan and G.Seaborg, W.Libby and others). In honor of the Curie spouses, the artificially obtained transuranium element with serial number 96, curium, got its name.

In 1898, the English scientist E. Rutherford began to study the phenomenon of radioactivity. In 1903, E. Rutherford proves the error of the assumption of the English physicist D. Thompson about his theory of the structure of the atom, and in 1908-1911. conducts experiments on the scattering of α-particles (helium nuclei) by metal foil. The α-particle passed through a thin foil (1 µm thick) and, hitting a screen of zinc sulfide, generated a flash, which was well observed under a microscope. Experiments on the scattering of α-particles convincingly showed that almost the entire mass of an atom is concentrated in a very small volume - the atomic nucleus, the diameter of which is approximately 100,000 times smaller than the diameter of the atom. Most α-particles fly past the massive nucleus without touching it, but occasionally there is a collision of α-particles with the nucleus and then it can bounce back. Thus, his first fundamental discovery in this area was the discovery of the inhomogeneity of the radiation emitted by uranium. So the concept of α- and β-rays first entered the science of radioactivity. He also suggested names: α - decay and α - particle. A little later, another component of the radiation was discovered, designated by the third letter of the Greek alphabet: γ-rays. This happened shortly after the discovery of radioactivity. For many years, α-particles have become for E. Rutherford an indispensable tool for the study of atomic nuclei. In 1903, he discovers a new radioactive element - the emanation of thorium. In 1901-1903, together with the English scientist F. Soddy, he conducted research that led to the discovery of the natural transformation of elements (for example, radium into radon) and the development of a theory of radioactive decay of atoms.

In 1903, the German physicist K. Fajans and F. Soddy independently formulated a displacement rule that characterizes the movement of an isotope in the periodic system of elements during various radioactive transformations.

In the spring of 1934, an article entitled "A New Type of Radioactivity" appeared in the Reports of the Paris Academy of Sciences. Its authors Irene Joliot-Curie and her husband Frederic Joliot-Curie discovered that boron, magnesium, and aluminum irradiated with α-particles become radioactive themselves and emit positrons during their decay. This is how artificial radioactivity was discovered. As a result of nuclear reactions (for example, when various elements are irradiated with α - particles or neutrons), radioactive isotopes of elements are formed that do not exist in nature. It is these artificial radioactive products that make up the overwhelming majority of all isotopes known today. In many cases, the products of radioactive decay themselves turn out to be radioactive, and then the formation of a stable isotope is preceded by a chain of several acts of radioactive decay. Examples of such chains are the series of periodic isotopes of heavy elements, which begin with 238 U, 235 U, 232 nucleides and end with stable lead isotopes 206 Pb, 207 Pb, 208 Pb. Thus, out of the total number of currently known about 2000 radioactive isotopes, about 300 are natural, and the rest are obtained artificially, as a result of nuclear reactions. There is no fundamental difference between artificial and natural radiation. In 1934, I. and F. Joliot-Curie, as a result of studying artificial radiation, discovered new variants of β-decay - the emission of positrons, which were originally predicted by Japanese scientists H. Yukkawa and S. Sakata. I. and F. Joliot-Curie carried out a nuclear reaction, the product of which was a radioactive isotope of phosphorus with a mass number of 30. It turned out that he emitted positron . This type of radioactive transformation is called β + decay (meaning by β - decay is the emission of an electron).

One of the outstanding scientists of our time, E. Fermi, devoted his main works to research related to artificial radioactivity. The theory of beta decay created by him in 1934 is still used by physicists to understand the world of elementary particles.

Theorists have long predicted the possibility of double β - transformation into 2 β - decay, in which two electrons or two positrons are simultaneously emitted, but in practice this way of "death" of a radioactive nucleus has not yet been discovered. But relatively recently it was possible to observe a very rare phenomenon of proton radioactivity - the emission of a proton from the nucleus, and the existence of two-proton radioactivity, predicted by the scientist V.I. Goldansky, was proved. All these types of radioactive transformations are confirmed only by artificial radioisotopes, and they do not occur in nature.

Subsequently, a number of scientists from different countries (J.Duning, V.A. Karnaukhov, G.N. Flerov, I.V. Kurchatov and others) discovered complex transformations, including β-decay, transformations, including the emission of delayed neutrons .

One of the first scientists in the former USSR who began to study the physics of atomic nuclei in general and radioactivity in particular was Academician IV Kurchatov. In 1934, he discovered the phenomenon of branching of nuclear reactions caused by neutron bombardment and investigated artificial radioactivity. a number of chemical elements. In 1935, when bromine was irradiated with neutron fluxes, Kurchatov and his collaborators noticed that the radioactive bromine atoms arising in this process decay at two different rates. Such atoms were called isomers, and the phenomenon discovered by scientists isomerism.

Science has established that fast neutrons are capable of destroying uranium nuclei. In this case, a lot of energy is released and new neutrons are formed, capable of continuing the process of fission of uranium nuclei. Later it was discovered that the atomic nuclei of uranium can be divided without the help of neutrons. So spontaneous (spontaneous) fission of uranium was established. In honor of the outstanding scientist in the field of nuclear physics and radioactivity, the 104th element of the periodic system of Mendeleev is named kurchatov.

The discovery of radioactivity had a huge impact on the development of science and technology. It marked the beginning of an era of intensive study of the properties and structure of substances. The new prospects that arose in energy, industry, the military field of medicine and other areas of human activity due to the mastery of nuclear energy were brought to life by the discovery of the ability of chemical elements to spontaneous transformations. However, along with the positive factors of using the properties of radioactivity in the interests of mankind, examples of their negative interference in our lives can also be given. These include nuclear weapons in all its forms, sunken ships and submarines with nuclear engines and nuclear weapons, disposal of radioactive waste in the sea and on land, accidents at nuclear power plants, etc. and directly for Ukraine, the use of radioactivity in nuclear energy has led to the Chernobyl tragedy.

ESSAY

on the topic: OPENING

On the border of the last two centuries, an event occurred that changed the fate of mankind.
The French physicist Antoine Becquerel, in one of his experiments, wrapped crystals of uranyl-potassium sulfate K 2 (UO 2) (SO 4) 2 in black opaque paper and placed the bundle on a photographic plate. After manifestation, he found the outlines of crystals on it. Thus, the natural radioactivity of uranium compounds was discovered.

Becquerel's observations interested French scientists, physicist and chemist Marie Sklodowska-Curie and her husband, physicist Pierre Curie. They started searching for new radioactive chemical elements in uranium minerals. The polonium Po and radium Ra found by them in 1898 turned out to be products of the decay of uranium atoms. This was already a real revolution in chemistry, since before that atoms were considered indivisible, and chemical elements - eternal and indestructible.

In the 20th century, many interesting discoveries took place in chemistry. Here are just a small part of them. From 1940 to 1988 20 new chemical elements not found in nature were synthesized, including technetium Tc and astatine At. It was possible to obtain elements that are in the Periodic system after uranium, from neptunium Np with atomic number 93 to an element that still does not have a generally recognized name, with atomic number 114.

There is a gradual merging of inorganic and organic chemistry and the formation on their basis of the chemistry of organometallic compounds, bioinorganic chemistry, the chemistry of silicon and boron, the chemistry of complex compounds. This process was initiated by the Danish organic chemist William Zeise, who synthesized the unusual compound potassium trichloroethyleneplatinate (II) K in 1827. Only in 1956 was it possible to establish the nature of the chemical bonds in this compound.

In the second half of the 20th century, it was possible to obtain artificially such very complex natural substances as chlorophyll and insulin. Compounds of noble gases from radon Rn to argon Ar, which were previously considered inert, incapable of chemical interaction, were also synthesized. A start was made on obtaining fuel from water and light.

The possibilities of chemistry turned out to be limitless, and the most unbridled fantasies of man in the field of synthesis of substances with unusual properties were feasible. The young generation of chemists in the first half of the 21st century will be engaged in their implementation.

Discovery of the electron

The hypothesis of the existence of an elementary electric charge. Faraday's experiments showed that for different electrolytes, the electrochemical equivalent k substances turns out to be different, but in order to isolate one mole of any monovalent substance on the electrode, it is required to skip the same charge F, equal to approximately 9.6 * 10 4 C. A more precise value for this quantity, called Faraday constant, is equal to F=96485 C*mol -1.

If 1 mole of ions, when an electric current is passed through an electrolyte solution, transfers an electric charge equal to the Faraday constant F, then each ion has an electric charge equal to

. (12.10)

On the basis of such a calculation, the Irish physicist D. Stoney suggested the existence of elementary electric charges inside atoms. In 1891, he proposed to call the minimum electric charge e electron.

Measurement of the charge of an ion. When a constant electric current is passed through the electrolyte for a time t one of the electrodes receives an electric charge equal to the product of the current strength I for a while t. On the other hand, this electric charge is equal to the product of the charge of one ion q0 on the number of ions N:

It = q 0 N. (12.11)

From here we get

(12.13)

then from expressions (12.12) and (12.13) we find

Thus, to experimentally determine the charge of one ion, it is necessary to measure the direct current strength I passing through the electrolyte, time t current carrying capacity and mass m substance released from one of the electrodes. You also need to know the molar mass of the substance. M.

The discovery of the electron. The establishment of the law of electrolysis has not yet proved strictly that elementary electric charges exist in nature. It can be assumed, for example, that all monovalent ions have different electric charges, but their average value is equal to the elementary charge e.
In order to find out whether an elementary charge exists in nature, it was necessary to measure not the total amount of electricity carried by a large number of ions, but the charges of individual ions. The question of whether the charge is necessarily associated with particles of matter and, if associated, with which ones, was also unclear.
An important contribution to the solution of these questions was made at the end of the 19th century. in the study of phenomena that occur when an electric current is passed through rarefied gases. In the experiments, the glow of the glass of the discharge tube behind the anode was observed. Against the light background of the glowing glass, a shadow from the anode was visible, as if the glow of the glass was caused by some kind of invisible radiation propagating in a straight line from the cathode to the anode. This invisible radiation is called cathode rays.
The French physicist Jean Perrin established in 1895 that "cathode rays" are in fact a stream of negatively charged particles.
Exploring the laws of motion of particles of cathode rays in electric and magnetic fields, the English physicist Joseph Thomson (1856-1940) found that the ratio of the electric charge of each of the particles to its mass is the same value for all particles. If we assume that each particle of cathode rays has a charge equal to the elementary charge e, then we have to conclude that the mass of a particle of cathode rays is less than one thousandth of the mass of the lightest of the known atoms - the hydrogen atom.
Thomson further established that the ratio of the charge of the particles of cathode rays to their mass is the same when the tube is filled with various gases and when the cathode is made from different metals. Consequently, the same particles were part of the atoms of different elements.
Based on the results of his experiments, Thomson concluded that the atoms of matter are not indivisible. From an atom of any chemical element, negatively charged particles with a mass less than one thousandth of the mass of a hydrogen atom can be torn out. All these particles have the same mass and have the same electric charge. These particles are called electrons.

Millikan experience. The final proof of the existence of an elementary electric charge was given by experiments that were carried out in 1909-1912. American physicist Robert Milliken (1868-1953). In these experiments, the speed of movement of oil drops in a uniform electric field between two metal plates was measured. A drop of oil that has no electric charge due to air resistance falls at a certain constant speed. If on its way the drop meets an ion and acquires an electric charge q, then, in addition to gravity, it is also affected by the Coulomb force from the electric field. As a result of a change in the force that causes the drop to move, the speed of its movement changes. By measuring the speed of the drop and knowing the strength of the electric field in which it moved, Millikan could determine the charge of the drop.
Millikan's experiment was repeated by one of the founders of Soviet physics, Abram Fedorovich Ioffe (1880-1960). In Ioffe's experiments, metal dust particles were used instead of oil drops to determine the elementary electric charge. By changing the voltage between the plates, the equality of the Coulomb force and the force of gravity was achieved (Fig. 12.2), the dust grain in this case was motionless:

mg=q 1 E 1.

Figure 12. 2

When a dust grain was illuminated with ultraviolet light, its charge changed, and in order to balance the force of gravity, it was necessary to change the electric field strength between the plates:

mg=q 2 E 2.

From the measured values of the electric field strength, it was possible to determine the ratio of the electric charges of the dust grain:

mg \u003d q 1 E 1 \u003d q 2 E 2 \u003d ... \u003d q n E n;

The experiments of Millikan and Ioffe showed that the charges of drops and dust particles always change stepwise. The minimum "portion" of electric charge is an elementary electric charge equal to

e \u003d 1.602 * 10 -19 Cl.

The electric charge of any body is always an integer multiple of the elementary electric charge. Other "portions" of electric charge capable of transferring from one body to another have not yet been experimentally detected in nature. At present, there are theoretical predictions about the existence of elementary particles - quarks - with fractional electric charges equal to 1/3 e and 2/Z e.

Becquerel's experience

The discovery of natural radioactivity, a phenomenon that proves the complex composition of the atomic nucleus, happened due to a happy accident. Becquerel studied the luminescence of substances previously irradiated with sunlight for a long time. Listening to reports of Roentgen's experiments at a meeting of the French Academy on January 20, 1896, and watching a demonstration of the appearance of X-rays in a discharge tube, Becquerel stares intently at a greenish luminous spot on the glass near the cathode. The thought that haunts him: maybe the glow of the samples of his collection is also accompanied by the emission of x-rays? Then X-rays can be obtained without resorting to the help of a discharge tube.

Becquerel ponders his experiment, chooses from his collection of double sulphate of uranium and potassium, puts the salt on a photographic plate, hidden from the light in black paper, and exposes the plate with salt to the sun.

After developing, the photographic plate turned black in those areas where the salt lay. Consequently, uranium created some kind of radiation that penetrates opaque bodies and acts on a photographic plate. Becquerel thought that this radiation occurs under the influence of sunlight. But one day, in February 1896, he failed to conduct another experiment due to cloudy weather. Becquerel put the record back in a drawer, placing on top of it a copper cross covered with uranium salt. Having developed the plate, just in case, two days later, he found blackening on it in the form of a distinct shadow of a cross. This meant that uranium salts spontaneously, without any external influences, create some kind of radiation. Intensive research began.

Soon, Becquerel established an important fact: the intensity of radiation is determined only by the amount of uranium in the preparation, and does not depend on which compounds it is included in. Consequently, radiation is inherent not in compounds, but in the chemical element uranium, its atoms.

The ability of uranium to emit rays did not weaken for months. On May 18, 1896, Becquerel clearly stated the presence of this ability in uranium compounds and described the properties of radiation. But pure uranium was at the disposal of Becquerel only in the autumn, and on November 23, 1896, Becquerel reported on the property of uranium to emit invisible uranium rays, regardless of its chemical and physical state.

Curie's research.

In 1878, Pierre Curie became a demonstrator in the physical laboratory of the Sorbonne, where he began to study the nature of crystals. Together with his older brother Jacques, who worked in the mineralogical laboratory of the university, Pierre carried out intensive experimental work in this area for four years. The Curie brothers discovered piezoelectricity - the appearance of electrical charges on the surface of certain crystals under the action of an external force. They also discovered the opposite effect: the same crystals experience compression under the action of an electric field.

If an alternating current is applied to such crystals, they can be made to oscillate at ultra-high frequencies, at which the crystals will emit sound waves beyond the range of human hearing. Such crystals have become very important components of such radio equipment as microphones, amplifiers and stereo systems.

The Curie brothers designed and built such a laboratory device as a piezoelectric quartz balancer, which creates an electric charge proportional to the applied force. It can be considered the forerunner of the main components and modules of modern quartz watches and radio transmitters. In 1882, on the recommendation of the English physicist William Thomson, Curie was appointed head of the laboratory of the new Municipal School of Industrial Physics and Chemistry. Although the salary at the school was more than modest, Curie remained head of the laboratory for twenty-two years. A year after the appointment of Pierre Curie as head of the laboratory, the collaboration between the brothers ended, as Jacques left Paris to become professor of mineralogy at the University of Montpellier.

In the period from 1883 to 1895, P. Curie completed a large series of works, mainly on crystal physics. His articles on the geometric symmetry of crystals have not lost their significance for crystallographers to this day. From 1890 to 1895, Curie studied the magnetic properties of substances at various temperatures. Based on a large number of experimental data in his doctoral dissertation, the relationship between temperature and magnetization was established, which later became known as the Curie law.

While working on his dissertation, Pierre Curie in 1894 met Maria Skłodowska, a young Polish student at the Faculty of Physics at the Sorbonne. They married on July 25, 1895, a few months after Curie completed his doctoral thesis. In 1897, shortly after the birth of their first child, Irene, Marie Curie began research on radioactivity, which soon absorbed Pierre's attention for the rest of his life.

In 1896, Henri Becquerel discovered that uranium compounds constantly emit radiation capable of illuminating a photographic plate. Having chosen this phenomenon as the topic of her doctoral dissertation, Marie began to find out if other compounds emit "Becquerel rays". Since Becquerel discovered that the radiation emitted by uranium increased the electrical conductivity of the air near the preparations, she used the Curie brothers' piezoelectric quartz balancer to measure the electrical conductivity.

Soon Marie Curie came to the conclusion that only uranium, thorium and compounds of these two elements emit Becquerel radiation, which she later called radioactivity. Maria, at the very beginning of her research, made an important discovery: uranium resin blende (uranium ore) electrifies the surrounding air much more than the uranium and thorium compounds contained in it, and even than pure uranium. From this observation, she concluded that there was still an unknown highly radioactive element in the uranium resin blende. In 1898, Marie Curie reported the results of her experiments to the French Academy of Sciences. Convinced that his wife's hypothesis was not only correct but very important, Pierre Curie left behind his own research to help Marie isolate the elusive element. Since that time, the interests of the Curies as researchers have merged so completely that even in their laboratory notes they always used the pronoun "we".

The Curies set themselves the task of separating uranium resin blende into chemical components. After laborious operations, they received a small amount of a substance that had the highest radioactivity. It turned out that the allocated portion contains not one, but two unknown radioactive elements. In July 1898, Pierre and Marie Curie published an article "On the radioactive substance contained in uranium resin blende", in which they reported the discovery of one of the elements, named polonium in honor of Maria Sklodowska's homeland of Poland.

In December, they announced the discovery of a second element, which they named radium. Both new elements were many times more radioactive than uranium or thorium, and amounted to one millionth of uranium resin blende. In order to isolate radium from the ore in sufficient quantities to determine its atomic weight, the Curies processed several tons of uranium resin blende over the next four years. Working in primitive and hazardous conditions, they performed chemical separation operations in huge vats set in a leaky barn, and all analyzes in the tiny, poorly equipped laboratory of the Municipal School.

In September 1902, the Curies reported that they were able to isolate one tenth of a gram of radium chloride and determine the atomic mass of radium, which turned out to be 225. glow and warmth. This fantastic-looking substance attracted the attention of the whole world. Recognition and awards for his discovery came almost immediately.

The Curies published a huge amount of information on radioactivity collected during their research: from 1898 to 1904 they published thirty-six papers. Even before completing their research. The Curies encouraged other physicists to also study radioactivity. In 1903, Ernest Rutherford and Frederick Soddy suggested that radioactive emissions are associated with the decay of atomic nuclei. Decaying (losing some of the particles that form them), radioactive nuclei undergo transmutation into other elements. The Curies were among the first to realize that radium could also be used for medical purposes. Noticing the effect of radiation on living tissues, they suggested that radium preparations could be useful in the treatment of tumor diseases.

The Royal Swedish Academy of Sciences awarded the Curies half the Nobel Prize in Physics in 1903 "in recognition ... of their joint research into the phenomena of radiation discovered by Professor Henri Becquerel", with whom they shared the prize. The Curies were ill and were unable to attend the awards ceremony. In his Nobel Lecture two years later, Curie pointed out the potential danger posed by radioactive substances if they fell into the wrong hands, and added that he "belongs to those who, along with the chemist and businessman Alfred Nobel, believe that new discoveries will bring mankind more trouble than good.”

Radium is an extremely rare element in nature, and prices for it, given its medical importance, have risen rapidly. The Curies lived in poverty, and the lack of funds could not but affect their research. At the same time, they resolutely abandoned the patent for their extraction method, as well as the prospect of commercial use of radium. According to them, this would be contrary to the spirit of science - the free exchange of knowledge. Despite the fact that such a refusal deprived them of considerable profit, the Curie's financial situation improved after receiving the Nobel Prize and other awards.

In October 1904, Pierre Curie was appointed professor of physics at the Sorbonne, and Marie Curie was appointed head of the laboratory, which had previously been directed by her husband. In December of that year, Curie's second daughter, Eva, was born. Increased incomes, improved research funding, plans for a new laboratory, and the admiration and recognition of the world scientific community were to make the subsequent years of the Curies fruitful. But, like Becquerel, Curie passed away too early, not having time to enjoy the triumph and accomplish his plan. On a rainy day on April 19, 1906, while crossing a street in Paris, he slipped and fell. His head fell under the wheel of a passing horse-drawn carriage. Death came instantly.

Marie Curie inherited his chair at the Sorbonne, where she continued her research on radium. In 1910 she succeeded in isolating pure metallic radium, and in 1911 she was awarded the Nobel Prize in Chemistry. In 1923, Marie published a biography of Curie. Curie's eldest daughter, Irene (Irene Joliot-Curie), shared the 1935 Nobel Prize in Chemistry with her husband; the youngest, Eva, became a concert pianist and biographer of her mother. Serious, restrained, completely focused on his work, Pierre Curie was at the same time a kind and sympathetic person. He was widely known as an amateur naturalist. One of his favorite pastimes was walking or cycling. Despite the busyness in the laboratory and family concerns, the Curies found time for joint walks.

In addition to the Nobel Prize, Curie was awarded several other awards and honorary titles, including the Davy Medal of the Royal Society of London (1903) and the Matteucci Gold Medal of the Italian National Academy of Sciences (1904). He was elected to the French Academy of Sciences (1905).

The work of Pierre and Marie Curie paved the way for research into the structure of nuclei and led to modern advances in the development of nuclear energy.

On March 1, 1896, the French physicist A. Bakkrel discovered, by blackening a photographic plate, the emission of invisible rays of strong penetrating power from uranium salt. He soon found out that uranium itself also has the property of radiation. Then he discovered such a property in thorium. Radioactivity (from the Latin radio - I radiate, radus - a beam and activus - effective), this name was given to an open phenomenon, which turned out to be the privilege of the heaviest elements of the periodic system of D.I. Mendeleev. There are several definitions of this remarkable phenomenon, one of which gives such a formulation : “Radioactivity is the spontaneous (spontaneous) transformation of an unstable isotope of a chemical element into another isotope (usually an isotope of another element); in this case, electrons, protons, neutrons or helium nuclei (particles) are emitted. The essence of the discovered phenomenon was a spontaneous change in the composition of the atomic nucleus, which is in the ground state or in an excited long-lived state.

By the way, she was the first to propose the term radioactivity. Scientists came to the conclusion that radioactivity is a spontaneous process that occurs in the atoms of radioactive elements.

Now this phenomenon is defined as the spontaneous transformation of an unstable isotope of one chemical element into an isotope of another element, and in this case, electrons, protons, neutrons, or helium nuclei are emitted? - particles. It should be noted here that among the elements contained in the earth's crust, all with serial numbers over 83 are radioactive, i.e. located in the periodic table after bismuth.

For 10 years of joint work, they have done a lot to study the phenomenon of radioactivity. It was selfless work in the name of science - in a poorly equipped laboratory and in the absence of the necessary funds. Pierre established the spontaneous release of heat by radium salts. Researchers received this preparation of radium in 1902 in the amount of 0.1 g. To do this, they needed 45 months of hard work and more than 10,000 chemical operations of liberation and crystallization. In 1903, the Curie and A. Beckerey were awarded the Nobel Prize in Physics for their discovery in the field of radioactivity.

In total, more than 10 Nobel Prizes in physics and chemistry were awarded for work related to the study and use of radioactivity (A. Beckerey, P. and M. Curie, E. Fermi, E. Rutherford, F. and I. Joliot-Curie, D.Havishi, O.Ganu, E.McMillan and G.Seaborg, W.Libby and others). In honor of the Curie spouses, the artificially obtained transuranium element with serial number 96, curium, got its name.

In 1898, the English scientist E. Rutherford began to study the phenomenon of radioactivity. conducting scattering experiments? – particles (helium nuclei) with metal foil – the particle passed through a thin foil (1 µm thick) and, hitting a zinc sulfide screen, generated a flash, which was well observed in a microscope. Scattering experiments? - particles convincingly showed that almost the entire mass of an atom is concentrated in a very small volume - the atomic nucleus, the diameter of which is about 10 times smaller than the diameter of the atom.

Majority? - particles fly past the massive nucleus without hitting it, but occasionally there is a collision? are particles with a nucleus, and then it can bounce back. Thus, his first fundamental discovery in this area was the discovery of the inhomogeneity of the radiation emitted by uranium. So the concept of? - and rays.

He also suggested names: ? - disintegration and - particle. A little later, another component of radiation was discovered, designated by the third letter of the Greek alphabet: rays. This happened shortly after the discovery of radioactivity. For many years? – particles have become for E. Rutherford an indispensable tool for the study of atomic nuclei. In 1903, he discovers a new radioactive element - the emanation of thorium. In 1901-1903, together with the English scientist F. Soddy, he conducts research that led to the discovery of the natural transformation of elements (for example, radium into radon) and the development of a theory of radioactive decay of atoms.

In 1903, the German physicist C. Faience and F. Soddy independently formulated a displacement rule that characterizes the movement of an isotope in the periodic system of elements during various radioactive transformations. In the spring of 1934, an article entitled “A New Type of Radioactivity” appeared in the Reports of the Paris Academy of Sciences ". Its authors Irene Joliot-Curie and her husband Frédéric Joliot-Curie found that boron, magnesium, and aluminum were irradiated? - particles, become themselves radioactive and emit positrons during their decay.

This is how artificial radioactivity was discovered. As a result of nuclear reactions (for example, when various elements are irradiated with particles or neutrons), radioactive isotopes of elements are formed that do not exist in nature. It is these artificial radioactive products that make up the vast majority of all isotopes known today.

In many cases, the products of radioactive decay themselves turn out to be radioactive, and then the formation of a stable isotope is preceded by a chain of several acts of radioactive decay. Examples of such chains are the series of periodic isotopes of heavy elements, which begin with 238U, 235U, 232 nucleides and end with stable lead isotopes 206Pb, 207Pb, 208Pb. Thus, out of the total number of currently known about 2000 radioactive isotopes, about 300 are natural, and the rest are obtained artificially, as a result of nuclear reactions.

There is no fundamental difference between artificial and natural radiation. In 1934, I. and F. Joliot-Curie, as a result of studying artificial radiation, discovered new variants of ?-decay - the emission of positrons, which were originally predicted by Japanese scientists H. Yukkawa and S. Sakata.I. and F. Joliot-Curie carried out a nuclear reaction, the product of which was a radioactive isotope of phosphorus with a mass number of 30. It turned out that he emitted a positron.

This type of radioactive transformation is called?+ decay (meaning by decay is the emission of an electron). One of the outstanding scientists of our time, E. Fermi, devoted his main works to research related to artificial radioactivity. The theory of beta decay, created by him in 1934, is currently used by physicists to understand the world of elementary particles. Theorists have long predicted the possibility of a double transformation into 2 decays, in which two electrons or two positrons are simultaneously emitted, but in practice this path of "death" no radioactive nucleus has yet been found.

But relatively recently it was possible to observe a very rare phenomenon of proton radioactivity - the emission of a proton from the nucleus, and the existence of two-proton radioactivity, predicted by the scientist V.I. Goldansky, was proved. All these types of radioactive transformations were confirmed only by artificial radioisotopes, and they do not occur in nature. Subsequently, a number of scientists from different countries (J.Duning, V.A. Karnaukhov, G.N. Flerov, I.V. Kurchatov, etc.) complex transformations, including the emission of delayed neutrons, were discovered, including ?-decay.

One of the first scientists in the former USSR who began to study the physics of atomic nuclei in general and radioactivity in particular was Academician I.V. Kurchatov. In 1934, he discovered the phenomenon of branching of nuclear reactions caused by neutron bombardment and studied artificial radioactivity. a number of chemical elements.

In 1935, when bromine was irradiated with neutron fluxes, Kurchatov and his collaborators noticed that the radioactive bromine atoms arising in this process decay at two different rates. Such atoms were called isomers, and the phenomenon discovered by scientists isomerism. Science has established that fast neutrons are capable of destroying uranium nuclei. In this case, a lot of energy is released and new neutrons are formed, capable of continuing the process of fission of uranium nuclei. Later it was found that the atomic nuclei of uranium can also be divided without the help of neutrons. So spontaneous (spontaneous) fission of uranium was established.

In honor of the outstanding scientist in the field of nuclear physics and radioactivity, the 104th element of the periodic system of Mendeleev is named kurchatovium. The discovery of radioactivity had a huge impact on the development of science and technology. It marked the beginning of an era of intensive study of the properties and structure of substances. The new prospects that arose in energy, industry, the military field of medicine and other areas of human activity due to the mastery of nuclear energy were brought to life by the discovery of the ability chemical elements to spontaneous transformations.

However, along with the positive factors of using the properties of radioactivity in the interests of mankind, examples of their negative interference in our lives can be given. These include nuclear weapons in all its forms, sunken ships and submarines with nuclear engines and nuclear weapons, and the disposal of radioactive waste in the sea and on land, accidents at nuclear power plants, etc. and directly for Ukraine, the use of radioactivity in nuclear energy led to the Chernobyl tragedy.

What will we do with the received material:

If this material turned out to be useful to you, you can save it to your page on social networks:

Radioactivity can be artificial when the decay of atomic nuclei is achieved through certain nuclear reactions. But before coming to artificial radioactive decay, science got acquainted with natural radioactivity - the spontaneous decay of the nuclei of some elements that occur in nature.

History of discovery

Any scientific discovery is the result of hard work, but the history of science knows when chance played a big role. This happened to the German physicist V.K. X-ray. This scientist was engaged in the study of cathode rays.

Once K.V. X-ray turned on the cathode tube covered with black paper. Not far from the tube were crystals of barium platinocyanide, which were not connected with the device. They started glowing green. Thus, radiation was discovered that occurs when cathode rays collide with any obstacle. The scientist called it X-rays, and in Germany and Russia the term "X-rays" is currently used.

Discovery of natural radioactivity

In January 1896, the French physicist A. Poincare at a meeting of the Academy spoke about the discovery of V.K. Roentgen and put forward a hypothesis about the connection of this radiation with the phenomenon of fluorescence - non-thermal luminescence of a substance under the influence of ultraviolet radiation.

The meeting was attended by physicist A.A. Becquerel. He was interested in this hypothesis, because he had long studied the phenomenon of fluorescence using the example of uranyl nitrite and other uranium salts. These substances, under the influence of sunlight, glow with a bright yellow-green light, but as soon as the action of sunlight ceases, the uranium salts cease to glow in less than a hundredth of a second. This was established by Father A.A. Becquerel, who was also a physicist.

After listening to A. Poincare, A.A. Becquerel suggested that uranium salts, having ceased to glow, could continue to emit some other radiation passing through an opaque material. The experiment conducted by the researcher seemed to prove this. The scientist put grains of uranium salt on a photographic plate wrapped in black paper and exposed it to sunlight. Having developed the plate, he found that it had turned black where the grains lay. A.A. Becquerel concluded that the radiation emitted by the salt of uranium is provoked by the sun's rays. But a happy accident again invaded the process of research.

Once A.A. Becquerel had to postpone another experiment due to cloudy weather. He put the prepared photographic plate into a drawer, and placed a copper cross covered with uranium salt on top. After some time, he nevertheless developed the plate - and the outlines of the cross were displayed on it. Since the cross and the plate were in a place inaccessible to sunlight, it remained to be assumed that uranium, the last element in the periodic table, emits invisible radiation spontaneously.

The study of this phenomenon, along with A.A. Becquerel was taken up by the spouses Pierre and Marie Curie. They found that two more elements they discovered had this property. One of them was named polonium - in honor of Poland, the birthplace of Marie Curie, and the other - radium, from the Latin word radius - a ray. At the suggestion of Marie Curie, this phenomenon was called radioactivity.

The article tells about who discovered the phenomenon of radioactivity, when it happened and under what circumstances.

Radioactivity

The modern world and industry are unlikely to be able to do without nuclear energy. Nuclear reactors power submarines, provide electricity to entire cities, and special energy sources based on are installed on artificial satellites and robots that study other planets.

Radioactivity was discovered at the very end of the 19th century. However, like many other important discoveries in various fields of science. But which of the scientists first discovered the phenomenon of radioactivity and how did this happen? We will talk about this in this article.

Opening

This very important event for science took place in 1896 and was made by A. Becquerel while studying the possible connection between luminescence and the recently discovered so-called x-rays.

According to the memoirs of Becquerel himself, he came up with the idea that, perhaps, any luminescence is also accompanied by X-rays? In order to test his guess, he used several chemical compounds, including one of the uranium salts, which glowed in the dark. Then, holding it under the sun's rays, the scientist wrapped the salt in dark paper and put it in a closet on a photographic plate, which, in turn, was also packed in an opaque wrapper. Later, having shown it, Becquerel replaced the exact image of a piece of salt. But since the luminescence could not overcome the paper, it means that it was X-ray radiation that illuminated the plate. So now we know who first discovered the phenomenon of radioactivity. True, the scientist himself did not yet fully understand what discovery he had made. But first things first.

Meeting of the Academy of Sciences

A little later in the same year, at one of the meetings at the Academy of Sciences of Paris, Becquerel made a report "On the radiation produced by phosphorescence." But after some time, adjustments had to be made to his theory and conclusions. So, during one of the experiments, without waiting for good and sunny weather, the scientist put a uranium compound on a photographic plate, which was not irradiated with light. Nevertheless, its clear structure was still reflected on the disc.

On March 2 of the same year, Becquerel presented a new work to the meeting of the Academy of Sciences, which described the radiation emitted by phosphorescent bodies. Now we know which of the scientists discovered the phenomenon of radioactivity.

Further experiments

Being engaged in further studies of the phenomenon of radioactivity, Becquerel tried many substances, including metallic uranium. And each time, traces invariably remained on the photographic plate. And by placing a metal cross between the radiation source and the plate, the scientist obtained, as they would say now, his x-ray. So we sorted out the question of who discovered the phenomenon of radioactivity.

It was then that it became clear that Becquerel discovered a completely new type of invisible rays that can pass through any objects, but at the same time they were not X-rays.

It was also found that the intensity depends on the amount of uranium itself in chemical preparations, and not on their types. It was Becquerel who shared his scientific achievements and theories with the spouses Pierre and Marie Curie, who subsequently established the radioactivity emitted by thorium and discovered two completely new elements, later called polonium and radium. And when analyzing the question “who discovered the phenomenon of radioactivity,” many often mistakenly attribute this merit to the Curies.

Impact on living organisms

When it became known that all uranium compounds emit, Becquerel gradually returned to the study of the phosphor. But he managed to make one more important discovery - the effect of radioactive rays on biological organisms. So Becquerel was not only the first to discover the phenomenon of radioactivity, but also the one who established its effect on living beings.

For one of the lectures, he borrowed a radioactive substance from the Curies and put it in his pocket. After the lecture, returning it to its owners, the scientist noticed a strong reddening of the skin, which had the shape of a test tube. after listening to his guesses, he decided on an experiment - for ten hours he wore a test tube containing radium tied to his arm. As a result, he received a severe ulcer that did not heal for several months.

So we sorted out the question of which of the scientists first discovered the phenomenon of radioactivity. This is how the influence of radioactivity on biological organisms was discovered. But despite this, the Curies, by the way, continued to study radiation materials, and died precisely from radiation sickness. Her personal belongings are still kept in a special lead-lined vault, since the dose of radiation accumulated by them almost a hundred years ago is still too dangerous.