The physical law of radioactive decay was formulated after Beckerel discovered the phenomenon of radioactivity in 1896. It consists in the unpredictable transition of some types of nuclei into others, while they emit different types of radiation and particles of elements. The process is natural when it is manifested in isotopes existing in nature, and artificial, in cases where they are obtained in nuclear reactions. The nucleus that decays is considered the mother, and the resulting - the daughter. In other words, the basic law of radioactive decay involves an arbitrary natural process of transforming one nucleus into another.
The Becquerel study showed the presence of previously unknown radiation in uranium salts, which had an effect on the photographic plate, filled the air with ions, and had the property of passing through thin metal plates. The experiments of M. and P. Curie with radium and polonium confirmed the conclusion described above, and a new concept appeared in science, called the doctrine of radioactive radiation.
This theory, reflecting the law of radioactive decay, is based on the assumption of a spontaneous process that obeys statistics. Since individual nuclei decay independently of each other, it is believed that, on average, the number of decayed over a certain period of time is proportionally undecided by the time the process ends. If you follow the exponential law, then the number of the latter decreases significantly.
The intensity of the phenomenon is characterized by two basic properties of radiation: the period of the so-called half-life and the average life span of a radioactive nucleus. The first ranges between millionths of a second and billions of years. Scientists believe that such nuclei do not age, and for them there is no concept of age.
The law of radioactive decay is based on the so-called displacement rules, and they, in turn, are a consequence of the theory of the conservation of the charge and mass number by the nucleus . It was established experimentally that the action of the magnetic field acts differently: a) the deflection of the rays occurs as positively charged particles; b) as negative; c) do not show any reaction. It follows from this that there are three types of radiation.
There are as many varieties of the decay process itself: with the emission of an electron; positron; absorption of one electron by the nucleus. It is proved that nuclei corresponding to their structure in lead survive decay with emission. The theory was called alpha decay and was formulated by G. A. Gamov in 1928. The second variety was formulated in 1931 by E. Fermi. His studies showed that instead of electrons, some types of nuclei emit opposite particles - positrons, and this is always accompanied by the emission of a particle with zero electric charge and a rest mass, a neurino. The simplest example of beta decay is the transition of a neuron into a proton with a time period of 12 minutes.
These theories, considering the laws of radioactive decay, were fundamental until 1940 of the 19th century, until the Soviet physicists G.N. Flerov and K.A. Petrzhak discovered another species, during which two equal particles spontaneously split up. In 1960, two-proton and two-neutron radioactivity was predicted. But to this day, this type of decay has not been experimentally confirmed and has not been detected. Only proton radiation was discovered, in which a proton is emitted from the nucleus.
Dealing with all these issues is quite difficult, although the law of radioactive decay itself is simple. It is not easy to understand its physical meaning and, of course, the presentation of this theory goes far beyond the scope of the physics program as an object in school.