Alpha and beta radiation are generally called radioactive decays. This is a process that is the emission of subatomic particles from the nucleus, occurring at a tremendous speed. As a result, an atom or its isotope can change from one chemical element to another. Alpha and beta decays of nuclei are characteristic of unstable elements. These include all atoms with a charge number greater than 83 and a mass number greater than 209.
Reaction conditions
Decomposition, like other radioactive transformations, is natural and artificial. The latter occurs due to the ingress of some foreign particle into the nucleus. How much alpha and beta decay an atom can undergo depends only on how soon a stable state is reached.
Under natural circumstances, alpha and beta minus decays occur.
Under artificial conditions, neutron, positron, proton and other, rarer types of decays and transformations of nuclei are present.
These names were given by Ernest Rutherford, who studied radioactive radiation.
The difference between stable and unstablecore
The ability to decay directly depends on the state of the atom. The so-called "stable" or non-radioactive nucleus is characteristic of non-decaying atoms. In theory, such elements can be observed indefinitely in order to be finally convinced of their stability. This is required in order to separate such nuclei from unstable ones, which have an extremely long half-life.
By mistake, such a "slow" atom can be mistaken for a stable one. However, tellurium, and more specifically, its isotope number 128, which has a half-life of 2.2·1024 years, can be a striking example. This case is not isolated. Lanthanum-138 has a half-life of 1011 years. This period is thirty times the age of the existing universe.
The essence of radioactive decay
This process happens randomly. Each decaying radionuclide acquires a rate that is constant for each case. The decay rate cannot change under the influence of external factors. It doesn't matter if a reaction will occur under the influence of a huge gravitational force, at absolute zero, in an electric and magnetic field, during any chemical reaction, and so on. The process can only be influenced by direct impact on the interior of the atomic nucleus, which is practically impossible. The reaction is spontaneous and depends only on the atom in which it proceeds and its internal state.
When referring to radioactive decays, the term "radionuclide" is often used. For those who are notfamiliar with it, you should know that this word denotes a group of atoms that have radioactive properties, their own mass number, atomic number and energy status.
Various radionuclides are used in technical, scientific and other areas of human life. For example, in medicine, these elements are used in diagnosing diseases, processing medicines, tools and other items. There are even a number of therapeutic and prognostic radio drugs.
No less important is the definition of the isotope. This word refers to a special kind of atoms. They have the same atomic number as an ordinary element, but a different mass number. This difference is caused by the number of neutrons, which do not affect the charge, like protons and electrons, but change their mass. For example, simple hydrogen has as many as 3 of them. This is the only element whose isotopes have been given names: deuterium, tritium (the only radioactive one) and protium. In other cases, the names are given according to the atomic masses and the main element.
Alpha decay
This is a kind of radioactive reaction. It is typical for natural elements from the sixth and seventh periods of the periodic table of chemical elements. Especially for artificial or transuranium elements.
Elements subject to alpha decay
The number of metals that are characterized by this decay include thorium, uranium and other elements of the sixth and seventh periods from the periodic table of chemical elements, counting from bismuth. The process also undergoes isotopes from among the heavyitems.
What happens during a reaction?
When alpha decay begins, the emission from the nucleus of particles consisting of 2 protons and a pair of neutrons. The emitted particle itself is the nucleus of a helium atom, with a mass of 4 units and a charge of +2.
As a result, a new element appears, which is located two cells to the left of the original in the periodic table. This arrangement is determined by the fact that the original atom has lost 2 protons and along with it - the initial charge. As a result, the mass of the resulting isotope is reduced by 4 mass units compared to the initial state.
Examples
During this decay, thorium is formed from uranium. From thorium comes radium, from it comes radon, which eventually gives polonium, and finally lead. In this process, isotopes of these elements are formed, and not they themselves. So, it turns out uranium-238, thorium-234, radium-230, radon-236 and so on, up to the appearance of a stable element. The formula for such a reaction is as follows:
Th-234 -> Ra-230 -> Rn-226 -> Po-222 -> Pb-218
The speed of the selected alpha particle at the moment of emission is from 12 to 20 thousand km/sec. Being in a vacuum, such a particle would circle the globe in 2 seconds, moving along the equator.
Beta Decay
The difference between this particle and an electron is in the place of appearance. Beta decay occurs in the nucleus of an atom, not in the electron shell surrounding it. The most common of all existing radioactive transformations. It can be observed in almost all currently existingchemical elements. It follows from this that each element has at least one isotope subject to decay. In most cases, beta decay results in beta-minus decay.
Reaction flow
In this process, an electron is ejected from the nucleus, which has arisen due to the spontaneous transformation of a neutron into an electron and a proton. In this case, due to the greater mass, protons remain in the nucleus, and the electron, called the beta minus particle, leaves the atom. And since there are more protons per unit, the nucleus of the element itself changes upwards and is located to the right of the original in the periodic table.
Examples
The decay of beta with potassium-40 turns it into a calcium isotope, which is located on the right. Radioactive calcium-47 becomes scandium-47, which can turn into stable titanium-47. What does this beta decay look like? Formula:
Ca-47 -> Sc-47 -> Ti-47
The speed of a beta particle is 0.9 times the speed of light, which is 270,000 km/sec.
There are not too many beta-active nuclides in nature. There are very few significant ones. An example is potassium-40, which is only 119/10,000 in a natural mixture. Also, among the significant natural beta-minus active radionuclides are the alpha and beta decay products of uranium and thorium.
Beta decay has a typical example: thorium-234, which in alpha decay turns into protactinium-234, and then in the same way becomes uranium, but its other isotope number 234. This uranium-234 again due to alpha decay becomesthorium, but already a different variety of it. This thorium-230 then becomes radium-226, which turns into radon. And in the same sequence, up to thallium, only with different beta transitions back. This radioactive beta decay ends with the formation of stable lead-206. This transformation has the following formula:
Th-234 -> Pa-234 -> U-234 -> Th-230 -> Ra-226 -> Rn-222 -> At-218 -> Po-214 -> Bi-210 -> Pb-206
Natural and significant beta active radionuclides are K-40 and elements from thallium to uranium.
Beta-plus decay
There is also a beta plus transformation. It is also called positron beta decay. It emits a particle called a positron from the nucleus. The result is the transformation of the original element into the one on the left, which has a lower number.
Example
When electron beta decay occurs, magnesium-23 becomes a stable isotope of sodium. Radioactive europium-150 becomes samarium-150.
The resulting beta decay reaction can create beta+ and beta- emissions. The particle escape velocity in both cases is 0.9 times the speed of light.
Other radioactive decays
In addition to such reactions as alpha decay and beta decay, the formula of which is widely known, there are other processes that are rarer and more characteristic of artificial radionuclides.
Neutron decay. A neutral particle of 1 unit is emittedmasses. During it, one isotope turns into another with a smaller mass number. An example would be the conversion of lithium-9 to lithium-8, helium-5 to helium-4.
When a stable isotope of iodine-127 is irradiated with gamma rays, it becomes isotope number 126 and acquires radioactivity.
Proton decay. It is extremely rare. During it, a proton is emitted, having a charge of +1 and 1 unit of mass. The atomic weight decreases by one value.
Any radioactive transformation, in particular, radioactive decays, is accompanied by the release of energy in the form of gamma radiation. They call it gamma rays. In some cases, lower energy x-rays are observed.
Gamma decay. It is a stream of gamma quanta. It is electromagnetic radiation, harder than X-ray, which is used in medicine. As a result, gamma quanta appear, or energy flows from the atomic nucleus. X-rays are also electromagnetic but originate from the electron shells of the atom.
Alpha particles run
Alpha particles with a mass of 4 atomic units and a charge of +2 move in a straight line. Because of this, we can talk about the range of alpha particles.
The value of the run depends on the initial energy and ranges from 3 to 7 (sometimes 13) cm in the air. In a dense medium, it is a hundredth of a millimeter. Such radiation cannot penetrate a sheetpaper and human skin.
Because of its own mass and charge number, the alpha particle has the highest ionizing power and destroys everything in its path. In this regard, alpha radionuclides are the most dangerous for humans and animals when exposed to the body.
Beta particle penetration
Due to the small mass number, which is 1836 times less than a proton, negative charge and size, beta radiation has a weak effect on the substance through which it flies, but moreover, the flight is longer. Also the path of the particle is not straight. In this regard, they speak of penetrating ability, which depends on the received energy.
The penetrating power of beta particles produced during radioactive decay reaches 2.3 m in air, in liquids it is counted in centimeters, and in solids - in fractions of a centimeter. The tissues of the human body transmit radiation 1.2 cm deep. To protect against beta radiation, a simple layer of water up to 10 cm can serve. The flow of particles with a sufficiently high decay energy of 10 MeV is almost completely absorbed by such layers: air - 4 m; aluminum - 2.2 cm; iron - 7.55 mm; lead - 5, 2 mm.
Given their small size, beta radiation particles have a low ionizing capacity compared to alpha particles. However, when ingested, they are much more dangerous than during external exposure.
Neutron and gamma currently have the highest penetrating performance among all types of radiation. The range of these radiations in the air sometimes reaches tens and hundredsmeters, but with lower ionizing performance.
Most isotopes of gamma rays do not exceed 1.3 MeV in energy. Rarely, values of 6.7 MeV are reached. In this regard, to protect against such radiation, layers of steel, concrete and lead are used for the attenuation factor.
For example, in order to attenuate cob alt gamma radiation tenfold, lead shielding is needed about 5 cm thick, 9.5 cm is required for 100-fold attenuation. Concrete shielding will be 33 and 55 cm, and water shielding - 70 and 115 cm.
The ionizing performance of neutrons depends on their energy performance.
In any situation, the best way to protect against radiation is to stay as far away from the source as possible and spend as little time as possible in the high radiation area.
Fission of atomic nuclei
Under the fission of the nuclei of atoms is meant spontaneous, or under the influence of neutrons, the division of the nucleus into two parts, approximately equal in size.
These two parts become radioactive isotopes of elements from the main part of the table of chemical elements. Starting from copper to lanthanides.
During the release, a couple of extra neutrons escape and there is an excess of energy in the form of gamma quanta, which is much greater than during radioactive decay. So, in one act of radioactive decay, one gamma quanta appears, and during the act of fission, 8, 10 gamma quanta appear. Also, scattered fragments have a large kinetic energy, which turns into thermal indicators.
The released neutrons are capable of provoking the separation of a pair of similar nuclei if they are located nearby and the neutrons hit them.
This raises the possibility of a branching, accelerating chain reaction of splitting atomic nuclei and creating a large amount of energy.
When such a chain reaction is under control, it can be used for certain purposes. For example, for heating or electricity. Such processes are carried out at nuclear power plants and reactors.
If you lose control of the reaction, an atomic explosion will happen. Similar is used in nuclear weapons.
Under natural conditions, there is only one element - uranium, which has only one fissile isotope number 235. It is weapons-grade.
In an ordinary uranium atomic reactor from uranium-238, under the influence of neutrons, they form a new isotope at number 239, and from it - plutonium, which is artificial and does not occur naturally. In this case, the resulting plutonium-239 is used for weapons purposes. This process of fission of atomic nuclei is the essence of all atomic weapons and energy.
Phenomena such as alpha decay and beta decay, the formula of which is studied in school, are widespread in our time. Thanks to these reactions, there are nuclear power plants and many other industries based on nuclear physics. However, do not forget about the radioactivity of many of these elements. When working with them, special protection and compliance with all precautions are required. Otherwise, this may lead toirreparable disaster.
