In this article we will get acquainted with the term"radioactivity". This concept we will consider in general terms, from the point of view of the course of the decay process. Let us analyze the main types of radiation the decay law, historical data, and much more. Let's dwell on the concept of "isotope" and get acquainted with the phenomenon of electronic decay.
Radioactivity is a qualitative parameteratoms, which allows some isotopes to decay in a spontaneous order and emit radiation. The first confirmation of this statement was made by Becquerel, who conducted experiments on uranium. It is for this reason that the rays emitted by uranium were named in his honor. The phenomenon of radioactivity is the release of alpha or beta particles from the nucleus of an atom. Radioactivity expresses itself in the form of an expansion of the atomic nucleus of a certain element and allows the latter to transform from an atom of one element to another.
In the course of this process, decay occursof the initial atom with the subsequent transformation into an atom, which characterizes another element. The result of the ejection of four alpha particles from the atomic nucleus will be a decrease in the mass number, which forms the atom itself, by four units. This leads to a shift in the periodic table by a couple of positions to the left. This phenomenon is caused by the fact that during the "alpha shot" 2 protons and 2 neutrons were thrown out. And the number of the element, as we recall, corresponds to the number of protons in the nucleus. If a beta particle was ejected (e-) then the neutron is transformed fromnucleus into one proton. This leads to a shift in the periodic table by one cell to the right. The mass is changed to extremely small values. The emission of negatively charged electrons is coupled with the emission of gamma rays.
Radioactivity is a phenomenon in the course of whichthe isotope decays in a radioactive form. This process is subject to the law: the pure atoms (n), which decay in unit time, are proportional to the number of atoms (N) that are available at a particular time:
n = λN.
In this formula, the coefficient λ meansa constant decay of a radioactive character that is related to the half-life of the isotope (T) and corresponds to the following statement: λ = 0.693 / T. From this law it follows that after the expiration of a period of time equal to the half-life period, the quantitative value of the isotope will be less than twice. If the atoms that were formed during the radioactive (r-decay) decay become of the same nature, then their accumulation begins, which will last until the radioactive equilibrium is established between the two isotopes: the daughter and the parent.
Radioactivity and decay are interrelated objects of study. The first (p-nost) becomes possible thanks to the second (the decay process).
The concept of radioactive decay characterizesitself, as a transformation of the composition or structure of the structure of an atomic unstable nucleus. Moreover, the phenomenon is spontaneous. There is an emission of an elementary particle (or particle) or gamma quantum, as well as the release of nuclear fragments. The nuclides corresponding to this process are called radioactive. However, this term is also used to describe substances whose nuclei are also radioactive.
Natural radioactivity is the decay of nucleiatoms that are found in nature in a spontaneous order. The artificial process is the same process that we mentioned above, but it is carried out by man using artificial paths that correspond to special nuclear reactions.
The mother and daughter are those kernels thatdecay, and those that are formed as the final product of this decay. The mass number and charge of the daughter structure are described in the Soddy displacement rule.
The phenomenon of radioactivity includes differentspectra, which depend on the type of energy. In this case, the spectrum of alpha particles and y quarks is related to the discontinuous (discrete) type of the spectrum, and the beta particles are continuous.
For today, we are not only knownalpha-gamma and beta decays, but also the emission of protons and neutrons was detected. The concept of cluster radioactivity and spontaneous fission was also discovered. The capture of electrons, positrons and double decay of beta particles enter the beta-decay section and are considered as its variety.
There are isotopes that can be exposedsimultaneously to two or more types of decay. An example is bismuth 212, which, with 2/3 probabilities, forms thallium 208 (with the use of alpha-type decay) and 1/3 will lead to the appearance of polonium 212 (in the operation of beta decay).
The nucleus, which was formed during such a breakdown,sometimes can have the same radioactive properties, and after a while will be destroyed. The phenomenon of p-th decay is simpler in the absence of a stable nucleus. A sequence of similar processes is called a chain of decay, and the nucleotides that arise are called radioactive nuclei. The series of such elements that begin with uranium 238 and 235, as well as thorium 232, eventually come to a state of stable nucleotides, respectively lead 206 and 207 and 208.
The phenomenon of radioactivity allows some nuclei(isobars) with the same mass number to transform into each other. This is possible due to beta decay. Each isobaric chain includes from one to three stable beta-type nuclides (they do not have the ability to beta-decay, but they can be unstable, for example, with respect to other types of p-decay). The rest of the set of nuclei of this circuit is beta-unstable. By using β-minus or β-plus decay, the nucleus can be converted into a nuclide with β-stable form. If there are such nuclides in the isobaric chain, then the nucleus may begin to undergo beta-positive or negative decay. This phenomenon is called electron capture. An example is the decomposition of the potassium radionuclide 40 into neighboring β-stable states of argon 40 and calcium 40.
Radioactivity is, first of all, decayisotopes. At present, man is aware of more than forty isotopes possessing radioactivity and being in natural conditions. The predominant number is located in the r-th series: uranium-radium, thorium and actinium. All these particles exist and spread in nature. They can be present in the rock, the waters of the world's oceans, plants and animals, etc., and they cause the phenomenon of natural natural radioactivity.
In addition to the natural range of p-isotopes, man created more than a thousand artificial species. The method of production most often realizes itself in nuclear reactors.
A lot of p-isotopes are used and used for medical purposes, for example, to fight cancer. They are very important in the field of diagnostics.
The essence of radioactivity lies in the fact that the atomscan spontaneously turn from one to another. In doing so, they acquire a more stable or stable core structure. P-core during the transformation actively allocates energy resources of the atom, which take the form of charged particles or reach the state of gamma quanta; the latter in turn form either the corresponding (gamma) or electromagnetic radiation.
We already know about the existence of radioactiveisotopes of an artificial and natural nature. It is important to understand that there is no special and / or fundamental difference between them. This is due to the properties of the nuclei, which can only be determined in accordance with the structuring of the nucleus, and they do not depend on the ways of creation.
Как и говорилось ранее, открытие радиоактивности It was thanks to the works of Becquerel, which were committed in 1896. This process was identified during the experiments on uranium. More specifically, the scientist tried to cause the emulsion to darken the photoemulsion and expose the ionization air. Madame Curie-Sklodowska was the first person to measure the intensity of radiation U. And simultaneously with the scientist from Germany Schmidt, she revealed the rarity of thorium. It was the couple of the Curie, after the discovery of invisible radiation, which called it radioactive. In 1898, they also made a discovery of polonium - another p-th element, which was deposited in uranium resin ores. Radium was discovered by the Curie couple also in 1898, but a little earlier. The work was done together with Bemon.
После того как было открыто множество р-ных elements, a considerable number of authors have been shown and demonstrated that they all cause the emission of three species that change their behavior under magnetic field conditions. The unit of radioactivity is becquerel (Bq, or Bq). Rutherford proposed to name the detected rays alpha, beta and gamma rays.
Alpha radiation is a set of particles withpositive charge. Beta rays are formed by electrons, particles with a negative charge and a low mass. Gamma rays are an analog of X-rays and are represented in the form of electromagnetic quanta.
In 1902 Rutherford and Soddy were explainedthe phenomenon of radioactivity by means of an arbitrary transformation of the atom of one element into another. This process obeyed the laws of chance and was accompanied by the allocation of energy resources, which took the form of gamma, beta and alpha rays.
Natural radioactivity was investigated by M.Curie together with Debiern. They received in 1910 metal - radium - in pure form, and investigated its properties. In particular, attention was paid to the measurement of permanent decay. Debiern and Giselle made the discovery of actinium, and Gan discovered atoms such as radiotheories and mesotoria. Boltonwood described ionium, and Gan and Maitner made the discovery of protactinium. Each isotope of the elements mentioned, which were opened, has radioactive properties. Pierre Curie and Laborde in 1903 described the phenomenon of decay of radium. They showed that the reaction products of 1 gram of Ra in one hour of decay produce about one hundred and forty calories. In the same year, Ramsay and Soddy found that a sealed ampoule containing radium contained helium in its gaseous form.
Proceedings of scientists such as Rutherford, Dorn, Debiernand Gisel, show us that in the general list of decay products U and Th includes some rapidly disintegrating substances - gases. They have their own radioactivity, but they are called thorium or radium emanations. This also applies to actinium. They proved that when radium decays, helium and radon are created. The law of radioactivity on the transformation of elements was first formulated by Soddy, Russell, and Fayans.
The discovery of the phenomenon that we are studying in thisarticle, the first time Becquerel. It was he who discovered the phenomenon of decay. Therefore, the units of radioactivity are called becquerels (Bq). However, Rutherford made one of the greatest contributions to the development of the theory of r-dimensionality. He concentrated his own resources of attention on the analysis of the studied decay and was able to establish the nature of these transformations, as well as to determine the radiation that accompanies them.
The basis of his conclusions isthe postulation of the presence of alpha, gamma and beta radiation, which are emitted by natural radioactive elements, and the measurement of radioactivity made it possible to isolate the following types:
Еще одним моментом в становлении и конкретизации The definition of radioactivity is the discovery by Rutherford of atomic atomic structures. What is no less important is the establishment of the relationship between a number of properties of the atom and the structure of its nucleus. After all, it is the "core" of a particle that determines the structure of the electron shell and all the properties of a chemical character. This is what allowed to fully decipher the principles and mechanism by which radioactive transformation takes place.
The first successful transformation of the nucleus was accomplished in1919 by Ernest Rutherford. He used the "bombardment" of the nucleus of the N atom with the use of polonium alpha particles. A consequence of this was the emission of protons by nitrogen, followed by conversion into oxygen nuclei-O17.
In 1934, the Curie couple received radioactiveisotopes of phosphorus through artificial radioactivity. They acted on aluminum with alpha particles. The obtained P30 nuclei had some differences from the natural p-th forms of the same element. For example, during the decay, not electronic particles were emitted, but positron particles. Further they were transformed into stable silicon nuclei (Si30). In 1934, the discovery of artificial radioactivity and the phenomenon of positron decay were accomplished.
One class of radioactivity iselectronic capture (K-capture). In it, electrons are captured directly from the shells of atoms. As a rule, the K-shell emits a certain number of neutrons, and then it is transformed into a new "core" of the atom with the same index of the mass number (A). However, the number of the atom (Z) becomes less by 1, in comparison with the original nucleus.
The process of transformation of the nucleus in the course of the electroniccapture and positron decay is an action similar to each other. Therefore, they can be seen simultaneously during the observation of a set of atoms of one species. Electronic capture is always accompanied by the emission of radiation in the X-ray form. This is explained by the transition of an electron from a more distant nuclear orbital to a closer one. This phenomenon, in turn, is explained by the fact that electrons are torn from orbits that are closer to the core, and their place is sought to fill the particles from remote levels.
The phenomenon of isomeric transition is based on the fact thatthe emission of alpha and / or beta particles leads to the excitation of certain nuclei that are in a state of excess energy. Emitted resources "flow" in the form of excited gamma quanta. The change in the state of the nucleus during the p-th decay leads to the formation and isolation of all three types of particles.
The study of the isotope of strontium 90 allowedto determine that only beta particles are emitted to it, and the nuclei, for example, sodium 24, can also emit gamma quanta. The overwhelming majority of atoms are extremely few in the excited state. This value is so short (10-I) and small, that it can not yet be measured. Accordingly, only a small percentage of the nuclei can be in a state of excitation for a relatively long period of time (up to months).
Ядра способные «жить» так долго, именуют isomers. The accompanying transitions, which are observed during the transformation from one state to another and are accompanied by the emission of gamma quantum particles, are called isomeric. Radioactivity of radiation in this case acquires high and life-threatening values. Kernels that emit only beta and / or alpha particles are called pure nuclei. If the gamma-ray emission in the nucleus is observed during its decay, then it is called a gamma-emitter. A pure radiator of the latter kind can only be called a nucleus undergoing a multitude of isomeric transitions, which is possible only if it exists for a long time in an excited state.