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Atom Size is determined by the radius of its outer electron shell. The dimensions of all atoms are ~ 10 -10 m. And the size of the nucleus is 5 orders of magnitude smaller, only 10 -15 m. This can be visualized this way: if an atom is enlarged to the size of a 20-story building, then the nucleus of an atom will look like a millimeter speck of dust in the central room of this house. However, it is difficult to imagine a house whose mass is almost entirely concentrated in this speck of dust. And that’s exactly what an atom is.

Atoms are very small and very light. An atom is so many times lighter than an apple, how many times is an apple lighter globe. If the world “gets heavier” so that an atom weighs like a drop of water, then people in such a world will become as heavy as planets: children like Mercury and Mars, and adults like Venus and Earth.

It is impossible to examine an atom even with a microscope. The best optical microscopes allow you to distinguish the details of an object if the distance between them is ~0.2 µm. In an electron microscope, this distance was reduced to ~2-3 Å. For the first time, it was possible to distinguish and photograph individual atoms using an ion projector. But no one saw how the atom works inside. All data on the structure of atoms was obtained from experiments on particle scattering.

Weight atomic nucleus several thousand times the mass of its electron shell. This is due to the fact that the nuclei of atoms consist of very heavy particles, compared to electrons, called protons. p and neutrons n. Their masses are almost identical and approximately 2000 times greater than the mass of an electron. Wherein proton is a positively charged particle, and neutron- neutral. The charge of a proton is equal in magnitude to the charge of an electron. The number of protons in the nucleus is equal to the number of electrons in the shell, this ensures the electrical neutrality of the atom. The number of neutrons can be different; in the nucleus of a light hydrogen atom there are no neutrons at all, but in the nucleus of a carbon atom there can be 6, 7, or 8.

Electron massm e ≈ 0.91. 10 -30 kg, proton massm p≈ 1.673. 10 -27 kg = 1836m e , neutron massm n = 1.675. 10 -27 kg≈ 1840 m e.

Atomic mass less than the amount masses of the nucleus and electrons by the amount Δm, called mass defect, which arises due to the Coulomb interaction between the nucleus and electrons. The mass defect of atoms (as opposed to nuclei) is very small, and although it increases with increasing Z, not a single atom exceeds the mass of an electron. Material from the site

Of course, an atom cannot be put on a scale and weighed; it is too small. The masses of atoms were first determined by chemists. Moreover, they measured them in relative units, taking the mass of a hydrogen atom as one and using Dalton’s law, according to which chemical substances are formed by combining atoms of chemical elements in a strictly defined proportion. And now the masses of atoms are most often measured in relative units, but 1/12 of the mass of a carbon atom C 12.1 a is used as an atomic mass unit (amu). e.m. = 1.66057. 10 -27 kg.

An atom is a unique particle of the universe. This article will try to convey to the reader information about this element of matter. Here we will consider the following questions: what is the diameter of an atom and its dimensions, what qualitative parameters does it have, what is its role in the Universe.

Introduction to the Atom

An atom is a composite particle of substances that has microscopic size and mass. This is the smallest part of the elements of a chemical nature with incredibly small size and mass.

Atoms are built from two basic structural elements, namely from electrons and the atomic nucleus, which, in turn, is formed by protons and neutrons. The number of protons may differ from the number of neutrons. In both chemistry and physics, atoms in which the number of protons is comparable to the number of electrons are called electrically neutral. If the number of protons is higher or lower, then the atom, acquiring a positive or negative charge, becomes an ion.

Atoms and molecules in physics for a long time were considered the smallest “building blocks” from which the Universe is built, and even after the discovery of even smaller constituent components remain among most important discoveries in the history of mankind. It is atoms connected through interatomic bonds that form molecules. The bulk of the atom's mass is concentrated in the nucleus, namely, in the weight of its protons, which make up about 99.9% of the total value.

Historical data

Thanks to the achievements of science in the fields of physics and chemistry, many discoveries have been made regarding the nature of the atom, its structure and capabilities. Numerous experiments and calculations were carried out, during which a person was able to answer the following questions: what is the diameter of an atom, its size, and much more.

It was first discovered and formulated by philosophers ancient Greece and Rome. In the 17th-18th centuries, chemists were able to use experiments to prove the idea of ​​an atom as the smallest particle of matter. They showed that many substances can be broken down repeatedly using chemical methods. However, later discoveries by physicists showed that even an atom can be divided, and it is built from subatomic components.

The International Congress of Chemistry Scientists in Karlsruhe, located in Germany, in 1860 decided on the concept of atoms and molecules, where an atom is considered the smallest part of chemical elements. Consequently, it is also part of substances of simple and complex types.

The diameter of the hydrogen atom was one of the very first to be studied. However, its calculations have been carried out many times and the latest of them, published in 2010, showed that it is 4% less than previously assumed (10 -8). The index of the overall magnitude of the atomic nucleus corresponds to the number 10 -13 -10 -12, and the order of magnitude of the entire diameter is 10 -8. This caused many contradictions and problems, since hydrogen itself rightfully belongs to the main components the entire observable Universe, and such an inconsistency forces many recalculations in relation to fundamental statements.

Atom and its model

Currently, five main models of the atom are known, differing among themselves, first of all, in the time frame and ideas about its structure. Let's look directly at the models:

• The pieces that make up matter. Democritus believed that any property of substances should be determined by its shape, mass and other series of practical characteristics. For example, fire can burn because its atoms are sharp. According to Democritus, even the soul is formed by atoms.
• Thomson's atomic model, created in 1904 by J. J. Thomson himself. He proposed that the atom can be taken as a positively charged body contained within electrons.
• Nagaoka's early planetary atomic model, created in 1904, believed that the atomic structure was similar to that of Saturn. The nucleus is small in size and has a positive charge index, surrounded by electrons that move around the rings.
• Atomic planetary model discovered by Bohr and Rutherford. In 1911, E. Rutherford, after conducting whole line experiments, began to believe that the atom is similar to a planetary system, where electrons have orbits in which they move around the nucleus. However, this assumption ran counter to the data of classical electrodynamics. To prove the validity of this theory, Niels Bohr introduced the concept of postulates that assert and show that the electron does not need to expend energy, since it is in a certain, special energy state. The study of the atom subsequently led to the appearance quantum mechanics, which was able to explain many of the contradictions that could be observed.
• The quantum mechanical atomic model states that the central core of the particle in question consists of a nucleus formed from protons, as well as neutrons and electrons moving around it.

Structural features

The size of the atom previously determined that it was an indivisible particle. However, many experiences and experiments have shown us that it is built from subatomic particles. Any atom consists of electrons, protons and neutrons, with the exception of hydrogen - 1, which does not include the latter.

The Standard Model shows that protons and neutrons are formed through interactions between quarks. They belong to fermions, along with leptons. Currently, there are 6 types of quarks. Protons owe their formation to two u-quarks and one d-quark, and the neutron - to one u-quark and two d-quarks. Nuclear interaction the strong type that binds quarks is transmitted using gluons.

The movement of electrons in atomic space is predetermined by their “desire” to be closer to the nucleus, in other words, to be attracted, as well as by the Coulomb forces of interaction between them. These same types of forces hold each electron in a potential barrier surrounding the nucleus. The orbit of electron motion determines the diameter of the atom, which is equal to a straight line passing from one point in the circle to another, as well as through the center.

An atom has its spin, which is represented by its own momentum and lies beyond understanding general nature matter. Described using quantum mechanics.

Dimensions and weight

Each atomic nucleus with the same number of protons belongs to a common chemical element. Isotopes include representatives of atoms of the same element, but having a difference in neutron quantity.

Since in physics the structure of an atom indicates that the bulk of their mass is made up of protons and neutrons, the total amount of these particles has mass number. Expression atomic mass in a state of calm occurs through the use of atomic mass units (a.m.u.), which are otherwise called daltons (Da).

The size of an atom has no clearly defined boundaries. Therefore, it is determined by measuring the distance between nuclei of the same type of atoms that are chemically bonded to each other. Another measurement method is possible by calculating the duration of the path from the nucleus to the next available electron orbit of a stable type. elements of D.I. Mendeleev arranges the atoms in size, from smallest to largest, in the direction of the column from top to bottom, movement from left to right is also based on a decrease in their sizes.

Decay time

All chem. elements have isotopes of one and higher. They contain an unstable core that is subject to radioactive decay, resulting in the emission of particles or electromagnetic radiation. Radioactive is an isotope whose strong interaction radius extends beyond the farthest points of its diameter. If we consider the example of aurum, then the isotope will be the Au atom, beyond the diameter of which radiating particles “fly” in all directions. Initially, the diameter of a gold atom corresponds to the value of two radii, each of which is equal to 144 pc, and particles extending beyond this distance from the nucleus will be considered isotopes. There are three types of decay: alpha, beta and gamma radiation.

The concept of valency and the presence of energy levels

We have already become familiar with the answers to such questions: what is the diameter of an atom, its size, we have become familiar with the concept of atomic decay, etc. However, in addition to this, there are also such characteristics of atoms as the size of energy levels and valence.

Electrons moving around the atomic nucleus have potential energy and are in a bound state, located at an excited level. According to the quantum model, an electron occupies only a discrete number of energy levels.

Valence is the general ability of atoms that have an electron shell free place, make connections chemical type with other atomic units. By establishing chemical bonds, atoms try to fill their layer of the outer valence shell.

Ionization

As a result of the influence of a high voltage value on an atom, it can undergo irreversible deformation, which is accompanied by electronic detachment.

This results in the ionization of atoms, during which they give up electron(s) and undergo a transformation from a stable state into ions with a positive charge, otherwise known as cations. This process requires a certain energy, which is called ionization potential.

Summing up

Studying questions about structure, interaction features, qualitative parameters, what is the diameter of an atom and what dimensions does it have, all this has allowed the human mind to perform incredible work, helping to better understand and understand the structure of all matter around us. These same questions allowed man to discover the concepts of the electronegativity of an atom, its dispersed attraction, valence possibilities, and determine the duration radioactive decay and much more.

DEFINITION

Atom– the smallest chemical particle.

The diversity of chemical compounds is due to various combinations atoms of chemical elements into molecules and non-molecular substances. The ability of an atom to enter into chemical compounds, its chemical and physical properties are determined by the structure of the atom. In this regard, for chemistry it is of paramount importance internal structure atom and, first of all, the structure of its electron shell.

Atomic structure models

At the beginning of the 19th century, D. Dalton revived the atomic theory, relying on the fundamental laws of chemistry known at that time ( consistency of composition, multiple ratios and equivalents). The first experiments were carried out to study the structure of matter. However, despite the discoveries made (atoms of the same element have the same properties, and atoms of other elements have different properties, the concept of atomic mass was introduced), the atom was considered indivisible.

After obtaining experimental evidence (end XIX beginning XX century) the complexity of the structure of the atom (photoelectric effect, cathode and X-rays, radioactivity) it was established that the atom consists of negatively and positively charged particles that interact with each other.

These discoveries gave impetus to the creation of the first models of atomic structure. One of the first models was proposed J. Thomson(1904) (Fig. 1): the atom was imagined as a “sea of ​​positive electricity” with electrons oscillating in it.

After experiments with α-particles, in 1911. Rutherford proposed the so-called planetary model atomic structure (Fig. 1), similar to the structure solar system. According to the planetary model, at the center of the atom there is a very small nucleus with a charge Z e, the size of which is approximately 1,000,000 times smaller sizes the atom itself. The nucleus contains almost the entire mass of the atom and has a positive charge. Electrons move around the nucleus in orbits, the number of which is determined by the charge of the nucleus. The external trajectory of electron motion determines external dimensions atom. The diameter of an atom is 10 -8 cm, while the diameter of the nucleus is much smaller -10 -12 cm.

Rice. 1 Models of atomic structure according to Thomson and Rutherford

Experiments on studying atomic spectra showed imperfection planetary model structure of the atom, since this model contradicts the line structure of atomic spectra. Based on Rutherford's model, Einstein's teachings about light quanta and quantum theory radiation planck Niels Bohr (1913) formulated postulates, which consists theory of atomic structure(Fig. 2): an electron can rotate around the nucleus not in any, but only in some specific orbits (stationary), moving in such an orbit it does not radiate electromagnetic energy, radiation (absorption or emission of a quantum of electromagnetic energy) occurs during the transition (jump-like) of an electron from one orbit to another.

Rice. 2. Model of the structure of the atom according to N. Bohr

The accumulated experimental material characterizing the structure of the atom has shown that the properties of electrons, as well as other micro-objects, cannot be described on the basis of the concepts of classical mechanics. Microparticles obey the laws of quantum mechanics, which became the basis for the creation modern model atomic structure.

The main theses of quantum mechanics:

- energy is emitted and absorbed by bodies in separate portions - quanta, therefore, the energy of particles changes abruptly;

- electrons and other microparticles have a dual nature - they exhibit the properties of both particles and waves (wave-particle duality);

— quantum mechanics denies the presence of certain orbits for microparticles (for moving electrons it is impossible to determine the exact position, since they move in space near the nucleus, you can only determine the probability of finding an electron in different parts of space).

The space near the nucleus in which the probability of finding an electron is quite high (90%) is called orbital.

Quantum numbers. Pauli's principle. Klechkovsky's rules

The state of an electron in an atom can be described using four quantum numbers.

n– main quantum number. Characterizes the total energy reserve of an electron in an atom and the number of the energy level. n takes on integer values ​​from 1 to ∞. The electron has the lowest energy when n=1; with increasing n – energy. The state of an atom when its electrons are at such energy levels that their total energy is minimal is called ground state. States with higher values ​​are called excited. Energy levels are indicated Arabic numerals according to the value of n. Electrons can be arranged in seven levels, therefore, n actually exists from 1 to 7. The main quantum number determines the size of the electron cloud and determines the average radius of an electron in an atom.

l– orbital quantum number. Characterizes the energy reserve of electrons in the sublevel and the shape of the orbital (Table 1). Accepts integer values ​​from 0 to n-1. l depends on n. If n=1, then l=0, which means that there is a 1st sublevel at the 1st level.

m e– magnetic quantum number. Characterizes the orientation of the orbital in space. Accepts integer values ​​from –l through 0 to +l. Thus, when l=1 (p-orbital), m e takes on the values ​​-1, 0, 1 and the orientation of the orbital can be different (Fig. 3).

Rice. 3. One of the possible orientations in space of the p-orbital

s– spin quantum number. Characterizes the electron's own rotation around its axis. Accepts values ​​-1/2(↓) and +1/2(). Two electrons in the same orbital have antiparallel spins.

The state of electrons in atoms is determined Pauli principle: an atom cannot have two electrons with the same set of all quantum numbers. The sequence of filling the orbitals with electrons is determined Klechkovsky rules: the orbitals are filled with electrons in order of increasing sum (n+l) for these orbitals, if the sum (n+l) is the same, then the orbital with the smaller n value is filled first.

However, an atom usually contains not one, but several electrons, and to take into account their interaction with each other, the concept of effective nuclear charge is used - an electron in the outer level is subject to a charge that is smaller than the charge of the nucleus, as a result of which the internal electrons screen the external ones.

Basic characteristics of an atom: atomic radius (covalent, metallic, van der Waals, ionic), electron affinity, ionization potential, magnetic moment.

Electronic formulas of atoms

All the electrons of an atom form its electron shell. The structure of the electron shell is depicted electronic formula, which shows the distribution of electrons across energy levels and sublevels. The number of electrons in a sublevel is indicated by a number, which is written to the upper right of the letter indicating the sublevel. For example, a hydrogen atom has one electron, which is located in the s-sublevel of the 1st energy level: 1s 1. The electronic formula of helium containing two electrons is written as follows: 1s 2.

For elements of the second period, electrons fill the 2nd energy level, which can contain no more than 8 electrons. First, electrons fill the s-sublevel, then the p-sublevel. For example:

5 B 1s 2 2s 2 2p 1

Relationship between the electronic structure of an atom and the position of the element in the Periodic Table

The electronic formula of an element is determined by its position in the Periodic Table D.I. Mendeleev. Thus, the period number corresponds to In elements of the second period, electrons fill the 2nd energy level, which can contain no more than 8 electrons. First, electrons fill In elements of the second period, electrons fill the 2nd energy level, which can contain no more than 8 electrons. First, electrons fill the s-sublevel, then the p-sublevel. For example:

5 B 1s 2 2s 2 2p 1

In atoms of some elements, the phenomenon of electron “leap” from the outer energy level to the penultimate one is observed. Electron leakage occurs in atoms of copper, chromium, palladium and some other elements. For example:

24 Cr 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1

an energy level that can contain no more than 8 electrons. First, electrons fill the s-sublevel, then the p-sublevel. For example:

5 B 1s 2 2s 2 2p 1

The group number for elements of the main subgroups is equal to the number of electrons in the outer energy level; such electrons are called valence electrons (they participate in the formation chemical bond). Valence electrons for elements of side subgroups can be electrons of the outer energy level and the d-sublevel of the penultimate level. The group number of elements of secondary subgroups of groups III-VII, as well as for Fe, Ru, Os corresponds total number electrons in the s-sublevel of the outer energy level and the d-sublevel of the penultimate level

Tasks:

Draw the electronic formulas of phosphorus, rubidium and zirconium atoms. Indicate the valence electrons.

Answer:

15 P 1s 2 2s 2 2p 6 3s 2 3p 3 Valence electrons 3s 2 3p 3

37 Rb 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 1 Valence electrons 5s 1

40 Zr 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 2 5s 2 Valence electrons 4d 2 5s 2

Let's look at another application of the uncertainty principle (38.3), but please don't take this calculation too literally; the general idea is correct, but the analysis was not done very carefully. This idea concerns the determination of the size of atoms; after all, according to classical views, electrons should emit light and, spinning in a spiral, fall onto the surface of the nucleus. But according to quantum mechanics, this is impossible, because otherwise we would know where the electron ended up and how fast it was spinning.

Let's say there is a hydrogen atom and we measure the position of the electron; we must not be able to predict exactly where it will end up, otherwise the spread of momentum will become infinite. Every time we look at an electron, it ends up somewhere; it has an amplitude of probability of being in different places, so there is a probability of finding it anywhere. However, not all of these places need to be near the core itself; Let us assume that there is a spread in distances of the order of , i.e., the distance from the nucleus to the electron is approximately on average equal to . Let us determine , requiring that the total energy of the atom be minimal.

The spread in impulses, in accordance with the uncertainty relation, should be approximately equal to ; Therefore, trying to somehow measure the momentum of an electron (for example, by scattering photons on it and observing the Doppler effect from a moving scatterer), we will not receive zero all the time (the electron does not stand still), but we will receive momentum of the order of . The kinetic energy of electrons will be approximately equal to . (What we are doing now is, in a sense, dimensional analysis: we estimate how kinetic energy can depend on Planck's constant, mass and size of the atom. The answer is obtained up to numerical factors like ; etc. We even not defined properly.) Next, potential energy equal to the quotient of minus at the distance from the center, say, (as we remember, this is the square of the electron charge divided by ). Now look: when it decreases, the potential energy also decreases, but the less , the greater the impulse required by the uncertainty principle and the greater kinetic energy. The total energy is

(38.10)

We do not know what is equal to , but we know that the atom, ensuring its existence, is forced to make a compromise so that its total energy is as low as possible. To find the minimum, we differentiate it with respect to , require that the derivative be equal to zero and find . The derivative is equal to

(38.11)

The equation gives for the quantity

(38.12)

This distance is called the Bohr radius, and we see that the dimensions of an atom are on the order of an angstrom. The number turned out to be correct. This is very good, it is even surprisingly good, because until now we have not had any theoretical considerations about the size of an atom. From a classical point of view, atoms are simply impossible: electrons must fall onto nuclei. Substituting formula (38.12) for into (38.10), we find the energy. She turns out to be equal

(38.(3)

What does negative energy mean? And the fact is that when an electron is in an atom, it has less energy than when it is free. In other words, in an atom it is bound. And it takes energy to tear it out of the atom; energy is required to ionize a hydrogen atom. It is possible, of course, that it will take twice or three times as much energy, or times less, since our calculations were very sloppy. However, we cheated and chose all the constants so that the result was absolutely correct! This quantity is called Rydberg energy; This is the ionization energy of hydrogen.

Only now it becomes clear why we don’t fall through the floor. When we walk, the entire mass of the atoms of our shoes is repelled from the floor, from the entire mass of its atoms. Atoms are crushed, electrons are forced to crowd into a smaller volume, and according to the uncertainty principle, their momentum increases on average, and an increase in momentum means an increase in energy. The resistance of atoms to compression is not a classical, but a quantum mechanical effect. According to classical concepts, one would expect that as electrons and protons move closer together, the energy will decrease; The most favorable arrangement of positive and negative charges in classical physics is when they sit on top of each other. This was well known to classical physics and presented a mystery: atoms still existed! Of course, scientists even then came up with different ways the way out of the deadlock, the correct (hopefully!) way has become known only to us!

By the way, when there are a lot of electrons around the nucleus, they also try to stay away from each other. The reason for this is not yet clear to you, but it is a fact that if one electron occupies a certain place, then another will no longer occupy this place. More precisely, due to the existence of two spin directions, these electrons can sit on top of each other and spin: one in one direction, the other in the other. But you won’t be able to place any third person in this place. You have to put them in new places, and that's what the real reason that the substance has elasticity. If it were possible to put all the electrons in one place, matter would be even denser than usual. And it is precisely because electrons cannot sit on each other that tables and other solid objects exist.

It is natural, therefore, that, wanting to understand the properties of a substance, one must use quantum mechanics; classical is clearly not enough for this.

Studying the passage of an alpha particle through thin gold foil (see section 6.2), E. Rutherford came to the conclusion that the atom consists of a heavy positively charged nucleus and electrons surrounding it.

Core called the central part of the atom,in which almost the entire mass of the atom and its positive charge are concentrated.

IN composition of the atomic nucleus included elementary particles : protons And neutrons (nucleons from the Latin word nucleus- core). Such a proton-neutron model of the nucleus was proposed by the Soviet physicist in 1932 D.D. Ivanenko. The proton has a positive charge e + = 1.06 10 –19 C and a rest mass m p= 1.673·10 –27 kg = 1836 m e. Neutron ( n) – neutral particle with rest mass m n= 1.675 10 –27 kg = 1839 m e(where is the electron mass m e, equal to 0.91·10 –31 kg). In Fig. 9.1 shows the structure of the helium atom according to the ideas of the late XX - beginning of the XXI V.

Core charge equals Ze, Where e– proton charge, Z– charge number, equal serial number chemical element V periodic table Mendeleev's elements, i.e. number of protons in the nucleus. The number of neutrons in the nucleus is denoted N. Usually Z > N.

Currently known kernels with Z= 1 to Z = 107 – 118.

Number of nucleons in the nucleus A = Z + N called mass number . Cores with the same Z, but different A are called isotopes. Cores that, with the same A have different Z, are called isobars.

The nucleus is denoted by the same symbol as the neutral atom, where X– symbol of a chemical element. For example: hydrogen Z= 1 has three isotopes: – protium ( Z = 1, N= 0), – deuterium ( Z = 1, N= 1), – tritium ( Z = 1, N= 2), tin has 10 isotopes, etc. In the overwhelming majority of isotopes of one chemical element they have the same chemical and similar physical properties. In total, about 300 stable isotopes and more than 2000 natural and artificially obtained ones are known. radioactive isotopes.

The size of the nucleus is characterized by the radius of the nucleus, which has a conventional meaning due to the blurring of the boundary of the nucleus. Even E. Rutherford, analyzing his experiments, showed that the size of the nucleus is approximately 10–15 m (the size of an atom is 10–10 m). There is an empirical formula for calculating the radius of the core:

Where R 0 = (1.3 – 1.7)·10 –15 m. This shows that the volume of the nucleus is proportional to the number of nucleons.

The density of nuclear matter is of the order of magnitude 10 17 kg/m 3 and is constant for all nuclei. It significantly exceeds the densities of the densest ordinary substances.

Protons and neutrons are fermions, because have spin ħ /2.

The nucleus of an atom has intrinsic angular momentum – nuclear spin :

,

(9.1.2)

Where I – internal(complete)spin quantum number.

Number I accepts integer or half-integer values ​​0, 1/2, 1, 3/2, 2, etc. Cores with even A have integer spin(in units ħ ) and obey statistics Bose–Einstein(bosons). Cores with odd A have half-integer spin(in units ħ ) and obey statistics Fermi–Dirac(those. nuclei - fermions).

Nuclear particles have their own magnetic moments, which determine the magnetic moment of the nucleus as a whole. The unit of measurement for the magnetic moments of nuclei is nuclear magneton μ poison:

Here e – absolute value electron charge, m p– proton mass.

Nuclear magneton in m p/m e= 1836.5 times less than the Bohr magneton, it follows that the magnetic properties of atoms are determined magnetic properties its electrons .

There is a relationship between the spin of a nucleus and its magnetic moment:

where γ poison – nuclear gyromagnetic ratio.

The neutron has a negative magnetic moment μ n≈ – 1.913μ poison since the direction of the neutron spin and its magnetic moment are opposite. The magnetic moment of the proton is positive and equal to μ R≈ 2.793μ poison. Its direction coincides with the direction of the proton spin.

Distribution electric charge protons along the nucleus are generally asymmetrical. The measure of deviation of this distribution from spherically symmetric is quadrupole electrical torque kernels Q. If the charge density is assumed to be the same everywhere, then Q determined only by the shape of the nucleus. So, for an ellipsoid of revolution

,

(9.1.5)

Where b– semi-axis of the ellipsoid along the spin direction, A– semi-axis in the perpendicular direction. For a nucleus elongated along the spin direction, b > A And Q> 0. For a core flattened in this direction, b < a And Q < 0. Для сферического распределения заряда в ядре b = a And Q= 0. This is true for nuclei with spin equal to 0 or ħ /2.

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