Atomic nucleus

The atomic nucleus is the Central dense, positively charged part of the atom, around which the moving electrons. Atomic nucleus determines the structure of electron shells and all the properties of the atom. The existence of the atomic nucleus was proven in 1913 E. Rutherford. The main characteristics of the atomic nucleus are: atomic number Z - relative nucleus charge; mass number And the relative mass of the nucleus, rounded to the nearest whole number; the mass of the nucleus MI, spin - mechanical angular momentum and magnetic moment. Atomic nucleus consists of protons and neutrons (see), which are called nucleons. Beta particles emitted by atomic nuclei at?-decay, are formed in the mutual transformations within the kernel, one of the protons in the neutron or Vice versa (see Radioactivity).
Atomic number is equal to the number of protons in an atomic nucleus or the ordinal number of the element in the periodic system of elements of D. I. Mendeleyev and the number of electrons in deionizovanoy the atom. Mass number As equal to the number of nucleons in the atomic nucleus. The number of neutrons in the atomic nucleus is equal to A - Z. Thus, the atomic nucleus He42 consists of two protons (p) and two neutrons (n). The atomic nucleus is stable, if there is a specific for this atomic nucleus : the ratio of p and n. The excess of p or n kernel feel β±-decays. Heavy nuclei with Z > 82 are unstable because they have too many protons, which repel each other Coulomb forces. These atomic nuclei undergo a chain of alpha - and beta-decay; the heavy atomic nuclei undergo, in addition, the division process. The binding energy of all the particles in an atomic nucleus in accordance with the law on the relationship of mass and energy is ECB = (Σmn+Σmp-MI)c2 where mn and mp is the mass of the feast. Value (Σmn+Σmp-MI) is called the mass defect. For sustainable atomic nuclei mass fault >0, for unstable <0. The energy that must be expended, to detach from the atomic nucleus of one particle, called the binding energy on the particle (or binding energy of the n or p in an atomic nucleus). This energy for medium nuclei is equal 7-8 MeV, for nuclei with a < 4 it is much smaller for heavy atomic nuclei. ERUs decreases with A. Stability of the atomic nucleus characterized by mass defect or binding energy. The prevalence of certain types of nuclei proportional to their stability. In nature, dominated by light nuclei with Z<30, the total number of nuclei with Z >30 does not exceed 10-5 part of all nuclei. The volume of the atomic nucleus is proportional to the number of nucleons And that is, the density of nuclear matter practically the same and equal to about 14 g/cm3. Radius atomic nucleus RI=1,2·10-13And1/3. These properties of atomic nuclei due to the fact that between the nucleons are very large largest nuclear power, the nature of which is qualitatively different from the nature of known science gravitational and electromagnetic forces. The basic properties of nuclear forces following: interaction of two nucleons is not dependent on their charges; nuclear forces act on a short distance of about 10-13 cm; nuclear forces have the ability to saturation, i.e., each nucleon in the kernel communicates only with several neighbouring nucleons; noncentral forces are partially tensor character (depend on the orientation of the spins of the nucleons). The atomic nucleus is a quantum mechanical system, which, like the atom, can be only in a state with a certain energy. In normal unexcited state atomic nucleus all levels filled with increasing excitation energy of the distance between the levels closer and with a strong excitation of overlap. The magnitude of the energy levels of the atomic nucleus is determined by the study of nuclear reactions (see). To date there is no single theory and model of the atomic nucleus, which should describe the totality of the observed nuclear processes, a separate model of the atomic nucleus describe only a limited range of phenomena. Still not completely understood the nature of nuclear forces and the laws of interaction of nucleons in the nucleus. Model of liquid drops proposed in 1937 N. Bohr developed and Y. I. Frenkel, describes a number of processes are observed with exultation; shell model of the kernel (M. Meyer explains the greatest quantity of experimental facts. In 1933-1934, it was found that at a certain number of protons and neutrons formed the most stable configuration. The existence of a highly stable nuclei with neutrons or protons 2, 8, 14, 20, 28, 50, 82, 126 ("the magic number) showed that the neutrons and protons in the nuclei are grouped in a relatively stable configuration that fit the filled shells having a maximum binding energy. Many of the discrepancies between the calculated values with the experimental may explain the warp engines that are ellipsoids of rotation, either compressed or stretched along the axis. Configuration nuclei is determined by their electric moments (spatial charge distribution in the kernel). The generalized model of a nucleus (synthesis shell and droplet model) describes satisfactorily the most nuclear processes occurring or non-excited nuclei, or at low excitation energies. Cm. the Atom.