Radioactive transformations. Radioactive transformations - Knowledge Hypermarket Radioactive transformations of atomic nuclei formula

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59. The law of radioactive decay.

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60 . Activity – the number of decay events (in general, acts of radioactive, nuclear transformations) per unit of time (usually per second).

The units of activity are becquerel curies.

Becquerel (Bq) is one decay event per second (1 decay/sec). The unit is named after the French physicist and Nobel Prize winner Antoine-Henri Becquerel.

Curie (Ci) is the activity of 1 gram of radium-226 in equilibrium with its daughter decay products. Curie (Ci) -3.7x1010Bq. If radionuclides are distributed in the volume of a substance, then the concept of “specific activity” (mass or volume) is used - the activity of a unit of mass or volume of a substance, measuring it in Bq/kg Ci/kg; Bq/lily Ki/l.

More precisely, this is the activity of a radionuclide (or a mixture of radionuclides) per unit weight or volume of the substance.

In the case when radionuclides are distributed over the soil surface, the concept of “surface activity” is used - the activity of a unit area, measured in Bq/m2 or Ci/m2; Bq/km2 or Ci/km2.

61. All atomic and subatomic particles emitted from the nucleus of an atom during radioactive decay, i.e. radioactive or ionizing radiation passing through matter:

Firstly, they lead to its ionization, to the formation of hot (high-energy) and extremely reactive particles: ions and free radicals (fragments of molecules that have no charge);

Secondly, they can lead to the activation of a substance, to the appearance of so-called induced activity, that is, to the transformation of stable atoms into radioactive ones - the appearance of radionuclides of activation origin. Therefore, the main characteristics of ionizing radiation are the energy of particles, their range in different media or penetrating ability, and also their ionizing ability (especially as a danger to biological objects).

Due to their mass and charge, a-particles have the greatest ionizing ability; they destroy everything in their path. And therefore a-active radionuclides are the most dangerous for humans and animals when ingested. Due to their small size, mass and charge, β-particles have much less ionizing ability than α-particles, but it is natural that when ingested, β-active isotopes are also much more dangerous than when exposed to external irradiation. Thick layers of concrete, lead, and steel are used as protection against n- and g-radiation, and in this case we are talking only about the attenuation factor, and not about complete protection. In any case, it should be remembered that the most rational “protection” from any radiation is the greatest possible distance from the radiation source (within reasonable limits, of course) and the shortest possible time spent in the zone of increased radiation.

62. Therefore, the main indicator for characterizing the influence of radiation sources is the assessment of the energy that they lose when passing through a substance (medium) and which is absorbed by this substance.

When measuring ionizing radiation, the concept of dose is used, and when assessing its effect on biological objects, additional correction factors are used. Absorbed dose (from the Greek - share, portion) is the energy of ionizing radiation (IR) absorbed by the irradiated substance and usually calculated per unit of its mass. Gray (Gy) is a unit of absorbed dose in the SI system of units. Rad is a non-systemic unit of absorbed dose. Absorbed dose is a universal concept that characterizes the result of interaction of the radiation field with the environment. Exposure dose (for X-ray and g-radiation) is determined by air ionization. X-ray (R) is a non-systemic unit of exposure dose. This is the amount of g- or x-ray radiation that in 1 cm3 of dry air (having a weight of 0.001293 g under normal conditions) forms 2.082 109 pairs of ions that carry a charge of 1 electrostatic unit of each sign (in the SGSE system). Equivalent dose is a dose calculated for biological objects (humans) taking into account the QC radiation quality factor. Equal to the product of the absorbed dose and CC. The equivalent dose can be measured in the same units as the absorbed dose. The unit of equivalent dose in the SI system is Sievert (Sv). Effective equivalent dose is an equivalent dose calculated taking into account the different sensitivity of different body tissues to radiation. It is equal to the equivalent dose received by a specific organ (tissue, taking into account their weight), multiplied by the corresponding “radiation risk coefficient”.

63. The calculation of an individual dose in the general case is carried out based on the following diagram, illustrating the main stages of the entry and distribution of radionuclides in the environment.

In general, the impact of radiation on biological objects and, first of all, on the human body causes three different negative effects.

The first is a genetic effect on the hereditary (sex) cells of the body. It can and does manifest itself only in offspring. This is the birth of children with various deviations from the norm (deformities of varying degrees, dementia, etc.), or the birth of a completely non-viable fetus, with deviations incompatible with life.

The second is a genetic effect for the hereditary apparatus of somatic cells - body cells. It manifests itself during the life of a particular person in the form of various (mainly cancer) diseases. The third effect is the immune-somatic effect. This is a weakening of the body’s defenses and immune system due to the destruction of cell membranes and other structures. It manifests itself in the form of a wide variety of diseases, including those seemingly completely unrelated to radiation exposure, in an increase in the number and severity of diseases, and in complications. Weakened immunity provokes the occurrence of any diseases, including cancer. Thus, due to the high radiosensitivity of internal organs and the duration of the process of partial removal of radioactive isotopes from the body, internal irradiation is more dangerous for humans than external irradiation.

64. Attention should be paid to the sharp discrepancy between the dose received, that is, the energy released in the body, and the biological effect.

The same doses received by a person from external and internal radiation, as well as doses received from different types of ionizing radiation, from different radionuclides (when they enter the body) cause different effects!

At the same time, an absolutely lethal dose for humans of 1000 roentgens in units of thermal energy is only 0.0024 calories.

This amount of thermal energy can only heat about 0.0024 ml of water (0.0024 cm3) by 1°C, that is, only 2.4 mg of water. With a glass of hot tea we get thousands of times more.

At the same time, doctors, scientists, and nuclear scientists operate with doses of milli- and even micro-roentgens. That is, they indicate an accuracy that does not actually exist.

65. All emergencies are classified according to four criteria:

1) the sphere of occurrence, which determines the nature of the origin of the emergency situation;

2) departmental affiliation, i.e. where, in what sector of the national economy this emergency situation occurred;

3) the scale of possible consequences. Here the significance (magnitude) of the event, the damage caused and the amount of forces and resources involved to eliminate the consequences are taken as a basis;

4) the speed of spread of the danger.

66. Citizens of the Republic of Belarus in the field of protecting the population and territories from emergency situations have the right:

to protect life, health and personal property in the event of emergency situations;

use, in accordance with emergency response plans, means of collective and individual protection and other property of republican government bodies, other state organizations subordinate to the Council of Ministers of the Republic of Belarus, local executive and administrative bodies and other organizations intended to protect the population from emergency situations;

to information about the risk they may be exposed to in certain places of stay in the country, and about the necessary security measures; to contact government bodies, other organizations, as well as individual entrepreneurs on issues of protecting the population and territories from emergency situations;

participate in the prescribed manner in measures to prevent and eliminate emergency situations;

for compensation for damage caused to their health and property as a result of emergency situations;

for free medical care, compensation and benefits for living and working in emergency zones;

to free state social insurance, receiving compensation and benefits for harm caused to their health during participation in emergency response activities; for pension provision in the event of loss of ability to work due to injury or illness received in the performance of duties to protect the population and territories from emergency situations, in the manner established for workers whose disability occurred as a result of a work injury;

for pension provision in the event of the loss of a breadwinner who died or died from an injury or disease received in the performance of duties to protect the population and territories from emergency situations, in the manner established for the families of citizens who died or died from an injury received in the performance of a civic duty to save human life, protection of property and law and order.

Citizens of the Republic of Belarus in the field of protecting the population and territories from emergency situations are obliged to: comply with legislation in the field of protecting the population and territories from emergency situations;

observe safety measures in everyday life and daily work activities, avoid violations of production and technological discipline, environmental safety requirements, which can lead to emergency situations;

study the basic methods of protecting the population and territories from emergency situations, methods of providing first aid to victims, rules for using collective and individual protective equipment, constantly improve their knowledge and practical skills in this area;

67. The state system of prevention and liquidation of emergency situations unites

republican government body exercising management in the field of prevention and response to emergency situations, ensuring fire, industrial, nuclear and radiation safety, civil defense (hereinafter referred to as the republican government body for emergency situations),

other republican government bodies,

other state organizations subordinate to the Council of Ministers of the Republic of Belarus,

local executive and administrative bodies,

other organizations whose powers include resolving issues of protecting the population and territories from emergency situations. The main objectives of the state system for preventing and responding to emergency situations are:

development and implementation of legal and economic standards to ensure the protection of the population and territories from emergency situations;

implementation of targeted and scientific and technical programs aimed at preventing emergency situations and increasing the sustainability of the functioning of organizations, as well as social facilities in emergency situations;

ensuring the preparedness for action of emergency management bodies, forces and means intended and allocated for the prevention and elimination of emergency situations; The main objectives of the state system for preventing and responding to emergency situations are:

creation of republican, sectoral, territorial, local and facility reserves of material resources for liquidation of emergency situations (hereinafter referred to as reserves of material resources for liquidation of emergency situations, unless otherwise specified);

collection, processing, exchange and distribution of information in the field of protecting the population and territories from emergency situations;

preparing the population to act in emergency situations;

forecasting and assessing the socio-economic consequences of emergency situations;

implementation of state examination, supervision and control in the field of protection of the population and territories from emergency situations; The main objectives of the state system for preventing and responding to emergency situations are:

emergency response;

implementation of measures for social protection of the population affected by emergency situations, carrying out humanitarian actions;

implementation of the rights and responsibilities of the population in the field of protection from emergency situations, as well as persons directly involved in their elimination;

international cooperation in the field of protecting populations and territories from emergency situations; The main objectives of the state system for preventing and responding to emergency situations are:

69. By the middle of the last century, humanity began to realize the seriousness of the environmental problems facing it, and a natural question arose - how much time do we have left, how many years will it take before the tragic consequences of our neglect of the natural environment become obvious? We no longer have another thirty years left to study and discuss environmental problems. We must either create a sustainable society, or we will become witnesses to the extinction of civilization on Earth. In 1983, the United Nations created the World Commission on Environment and Development.

At the same time, the following principles of sustainable development were formulated:

People have the right to a healthy and productive life in harmony with nature;

Today's development should not be carried out to the detriment of development interests and environmental protection for the benefit of present and future generations;

Environmental protection must be an integral part of the development process and cannot be seen in isolation;

Environmental problems are solved in the most effective way with the participation of all concerned citizens. States develop and enhance public awareness and participation by providing widespread access to environmental information.

70. The biosphere is the region of existence and functioning of living organisms, covering the lower part of the atmosphere (aerobiosphere), the entire hydrosphere (hydrobiosphere), the land surface (terrabiosphere), and the upper layers of the lithosphere (lithobiosphere). The biosphere includes both living organisms (living matter) and their habitat and is an integral dynamic system that captures, accumulates and transfers energy through the exchange of substances between organisms and the environment.

71. All chemical compounds available to living organisms in the biosphere are limited.

The depletion of chemicals suitable for absorption often inhibits the development of certain groups of organisms in local areas of land or ocean.

According to academician V.R. Williams, the only way to give the finite properties of the infinite is to make it rotate along a closed curve.

Consequently, the stability of the biosphere is maintained due to the cycle of substances and energy flows.

There are two main cycles of substances: large - geological and small - biogeochemical. The great cycle is also called the water cycle between the hydrosphere, atmosphere and lithosphere, which is moved by the energy of the Sun. Unlike energy, which once used by the body is converted into heat and lost, substances circulate in the biosphere, creating biogeochemical cycles.

72. Maintaining the vital activity of organisms and the circulation of matter in ecosystems is possible only due to a constant flow of energy. Ultimately, all life on Earth exists due to the energy of solar radiation, which is converted by photosynthetic organisms (autotrophs) into potential energy - into organic compounds. Maintaining the vital activity of organisms and the circulation of matter in ecosystems is possible only due to a constant flow of energy.

It was one of the most important stages in the development of modern physical knowledge. Scientists did not immediately come to the correct conclusions regarding the structure of the smallest particles. And much later, other laws were discovered - for example, the laws of motion of microparticles, as well as features of the transformation of atomic nuclei that occur during radioactive decay.

Rutherford's experiments

The radioactive transformations of atomic nuclei were first studied by the English researcher Rutherford. Even then it was clear that the bulk of the mass of an atom lies in its nucleus, since electrons are many hundreds of times lighter than nucleons. In order to study the positive charge inside the nucleus, in 1906 Rutherford proposed probing the atom with alpha particles. Such particles arose during the decay of radium, as well as some other substances. During his experiments, Rutherford gained an understanding of the structure of the atom, which was given the name “planetary model”.

First observations of radioactivity

Back in 1985, the English researcher W. Ramsay, who is known for his discovery of argon gas, made an interesting discovery. He discovered helium gas in a mineral called kleveite. Subsequently, large amounts of helium were also found in other minerals, but only in those containing thorium and uranium.

This seemed very strange to the researcher: where could gas come from in minerals? But when Rutherford began to study the nature of radioactivity, it turned out that helium was a product of radioactive decay. Some chemical elements “give birth” to others, with completely new properties. And this fact contradicted all the previous experience of chemists of that time.

Frederick Soddy's observation

Together with Rutherford, scientist Frederick Soddy was directly involved in the research. He was a chemist, and therefore all his work was carried out in relation to the identification of chemical elements according to their properties. In fact, the radioactive transformations of atomic nuclei were first noticed by Soddy. He managed to find out what the alpha particles that Rutherford used in his experiments are. After making measurements, scientists found that the mass of one alpha particle is 4 atomic mass units. Having accumulated a certain number of such alpha particles, the researchers discovered that they turned into a new substance - helium. The properties of this gas were well known to Soddy. Therefore, he argued that alpha particles were able to capture electrons from outside and turn into neutral helium atoms.

Changes inside the nucleus of an atom

Subsequent studies were aimed at identifying the features of the atomic nucleus. Scientists realized that all transformations occur not with electrons or the electron shell, but directly with the nuclei themselves. It was the radioactive transformations of atomic nuclei that contributed to the transformation of some substances into others. At that time, the features of these transformations were still unknown to scientists. But one thing was clear: as a result, new chemical elements somehow appeared.

For the first time, scientists were able to trace such a chain of metamorphoses in the process of converting radium into radon. The reactions that resulted in such transformations, accompanied by special radiation, were called nuclear by researchers. Having made sure that all these processes take place precisely inside the nucleus of an atom, scientists began to study other substances, not just radium.

Open types of radiation

The main discipline that may require answers to such questions is physics (grade 9). Radioactive transformations of atomic nuclei are included in her course. While conducting experiments on the penetrating power of uranium radiation, Rutherford discovered two types of radiation, or radioactive transformations. The less penetrating type was called alpha radiation. Later, beta radiation was also studied. Gamma radiation was first studied by Paul Villard in 1900. Scientists have shown that the phenomenon of radioactivity is associated with the decay of atomic nuclei. Thus, a crushing blow was dealt to the previously prevailing ideas about the atom as an indivisible particle.

Radioactive transformations of atomic nuclei: main types

It is now believed that during radioactive decay three types of transformations occur: alpha decay, beta decay, and electron capture, otherwise called K-capture. During alpha decay, an alpha particle is emitted from the nucleus, which is the nucleus of a helium atom. The radioactive nucleus itself is transformed into one that has a lower electrical charge. Alpha decay is characteristic of substances that occupy the last places in the periodic table. Beta decay is also included in the radioactive transformations of atomic nuclei. The composition of the atomic nucleus with this type also changes: it loses neutrinos or antineutrinos, as well as electrons and positrons.

This type of decay is accompanied by short-wave electromagnetic radiation. In electron capture, the nucleus of an atom absorbs one of the nearby electrons. In this case, the beryllium nucleus can turn into a lithium nucleus. This type was discovered in 1938 by an American physicist named Alvarez, who also studied the radioactive transformations of atomic nuclei. The photographs in which the researchers tried to capture such processes contain images similar to a blurry cloud due to the small size of the particles being studied.

In the previous lesson we discussed the issue related to Rutherford's experiment, as a result of which we now know that the atom is a planetary model. This is what is called the planetary model of the atom. At the center of the nucleus is a massive, positively charged nucleus. And electrons revolve around the nucleus in their orbits.

Rice. 1. Rutherford's planetary model of the atom

Frederick Soddy took part in the experiments together with Rutherford. Soddy is a chemist, so he carried out his work precisely in terms of identifying the obtained elements by their chemical properties. It was Soddy who managed to find out what the a-particles were, the flow of which fell on the gold plate in Rutherford’s experiments. When measurements were made, it turned out that the mass of an a-particle is 4 atomic mass units, and the charge of an a-particle is 2 elementary charges. By comparing these things, having accumulated a certain number of a-particles, scientists found that these particles turned into a chemical element - helium gas.

The chemical properties of helium were known, thanks to which Soddy argued that the nuclei, which are a-particles, captured electrons from the outside and turned into neutral helium atoms.

Subsequently, the main efforts of scientists were aimed at studying the nucleus of the atom. It became clear that all the processes that occur during radioactive radiation occur not with the electron shell, not with the electrons that surround the nuclei, but with the nuclei themselves. It is in the nuclei that some transformations occur, as a result of which new chemical elements are formed.

The first such chain was obtained to transform the element radium, which was used in experiments on radioactivity, into the inert gas radon with the emission of an a-particle; the reaction in this case is written as follows:

Firstly, an a-particle is 4 atomic mass units and a double, doubled elementary charge, and the charge is positive. Radium has a serial number of 88, its mass number is 226, and radon has a serial number of 86, a mass number of 222, and an a-particle appears. This is the nucleus of a helium atom. In this case, we simply write helium. Ordinal number 2, mass number 4.

Reactions as a result of which new chemical elements are formed and at the same time new radiations and other chemical elements are also formed are called nuclear reactions.

When it became clear that radioactive processes take place inside the nucleus, they turned to other elements, not just radium. Studying various chemical elements, scientists realized that there are not only reactions with the emission, radiation of an a-particle from the nucleus of a helium atom, but also other nuclear reactions. For example, reactions with the emission of a b-particle. We now know that these are electrons. In this case, a new chemical element is also formed, respectively, a new particle, this is a b-particle, it is also an electron. Of particular interest in this case are all chemical elements whose atomic number is greater than 83.

So, we can formulate the so-called Soddy's rules, or displacement rules for radioactive transformations:

Rice. 2. Alpha decay

During beta decay, the atomic number increases by 1, but the atomic weight does not change.

Rice. 3. Beta decay

List of additional literature

1. Bronstein M.P. Atoms and electrons. “Library “Quantum””. Vol. 1. M.: Nauka, 1980
2. Kikoin I.K., Kikoin A.K. Physics: Textbook for 9th grade of high school. M.: “Enlightenment”
3. Kitaygorodsky A.I. Physics for everyone. Photons and nuclei. Book 4. M.: Science
4. Myakishev G.Ya., Sinyakova A.Z. Physics. Optics Quantum physics. 11th grade: textbook for in-depth study of physics. M.: Bustard
5. Rutherford E. Selected scientific works. Radioactivity. M.: Science
6. Rutherford E. Selected scientific works. The structure of the atom and the artificial transformation of elements. M.: Science

The most important types of radioactive transformations (Table 2) include a-decay, b-transformations, g-radiation and spontaneous fission, and in nature, under terrestrial conditions, almost only the first three types of radioactive transformations are found. Note that b-decays and g-radiation are characteristic of nuclides from any part of the periodic system of elements, and a-decays are characteristic of fairly heavy nuclei.

table 2

Basic radioactive transformations (Naumov, 1984)

a - decay- this is the radioactive transformation of nuclei with the emission of a-particles (helium nuclei):. Today more than 200 a-radioactive nuclei are known.
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All of them are heavy, Z>83. It is believed that any nucleus from this region has a-radioactivity (even if it has not yet been detected). Some isotopes of rare earth elements with the number of neutrons N>83 are also subject to a-decay. This region of a-active nuclei is located from (T 1/2 = 5∙10 15 years) to (T 1/2 = 0.23 s). The energies of decay a-particles are subject to rather strict limits: 4¸9 MeV for heavy nuclei and 2¸4.5 MeV for nuclei of rare earth elements, but isotopes emit a-particles with energies up to 10.5 MeV. All a-particles emitted from nuclei of a given type have approximately equal energies. a-particles carry away almost all the energy released during a-decay. The half-lives of a-emitters lie in a wide range: from 1.4∙10 17 years for to 3∙10 -7 s for .

b-transformations. For a long time, only electronic decay was known, which was called b-decay: . In 1934 ᴦ. F. Joliot-Curie and I. Joliot-Curie discovered during the bombardment of certain nuclei positronic, or b + -decay: . b-transformations also include electronic capture: . In these processes, the nucleus absorbs an electron from the atomic shell, usually from the K-shell; therefore, the process is also called K-capture. Finally, b-transformations include processes capture of neutrinos and antineutrinos:And . If a-decay is intranuclear process, then the elementary acts of b-transformations represent intranucleon processes: 1); 2); 3); 4); 5).

g-radiation of nuclei. The essence of the g-radiation phenomenon is that a nucleus in an excited state passes into lower energy states without changing Z and A, but with the emission of photons, and ultimately ends up in the ground state. Since the nuclear energies are discrete, the spectrum of g-radiation is also discrete. It extends from 10 keV to 3 MeV, ᴛ.ᴇ. The wavelengths lie in the region of 0.1¸ 4∙10 -4 nm. It is important to note that for comparison: for the red line of the visible spectrum lʼʼ600 nm, and Eg = 2 eV. In a chain of radioactive transformations, nuclei find themselves in an excited state as a result of previous b-decays.

The shift rules for Z and A given in the table allow us to group all naturally occurring radioactive elements into four large families or radioactive series (Table 3).

Table 3

Basic radioactive series (Naumov, 1984)

The actinium series got its name because the previous three members were discovered later than it. The parent of the neptunium series is relatively unstable and has not been preserved in the earth’s crust. For this reason, the neptunium series was first predicted theoretically, and then its structure was reconstructed in the laboratory (G. Seaborg and A. Ghiorso, 1950).

Each radioactive series contains members with higher values ​​of charge and mass number, but they have relatively short lifetimes and are practically never found in nature. All elements with Z>92 are called transuranium, and elements with Z>100 are called transfermium.

The amount of any radioactive isotope decreases over time due to radioactive decay (transformation of nuclei). The rate of decay is determined by the structure of the nucleus, as a result of which this process cannot be influenced by any physical or chemical means without changing the state of the atomic nucleus.

Radioactive transformations - concept and types. Classification and features of the category "Radioactive transformations" 2017, 2018.