How to distribute electrons by electronic layers. Distribution of electrons by levels, sublayers and orbitals in the multielectronic atom. Periodic system of Mendeleev elements

The energy state and the location of the electrons in the shells or layers of atoms is determined by four numbers, which are called quantum and are usually denoted by symbols N, L, S and J; Quantum numbers are interrupted, or discrete, character, i.e., can only receive separate, discrete, values, integers or half-purpose.

In relation to quantum numbers P, L, S and J, it is also necessary to keep in mind the following:

1. The quantum number N is called the main one; It is common to all electrons that are part of the same electronic shell; In other words, each of the electronic shells of the atom corresponds to a certain value of the main quantum number, namely: for electronic shells K, L, M, N, O, P and Q, the main quantum numbers are equal, respectively, 1, 2, 3, 4, 5, 6 and 7. In the case of a one-electrical atom (hydrogen atom), the main quantum number is used to determine the electron orbit and at the same time the atomic energy at a stationary state.

2. The quantum number I is called side, or orbital, and determines the moment of the amount of electron motion caused by its rotation around the atomic nucleus. Side quantum number may be 0, 1, 2, 3,. . . and in general is denoted by symbols S, P, D, F ,. . . Electrons having the same side quantum number form a subgroup, or, as they often say, are on the same energy pylon.

3. The quantum number S is often called spin, as it determines the moment of the amount of electron movement caused by its own rotation (the moment of the back).

4. The quantum number J is called the internal and determined by the sum of the vectors L and S.

Distribution of electrons in atoms (atomic shells) should also be some general provisions, it must be specified:

1. The principle of Pauli, according to which in the atom cannot be greater than one electron with the same values \u200b\u200bof all four quantum numbers, i.e., two electrons in the same atom should differ among themselves at least one quantum number.

2. The principle of energy, according to which all its electrons must be in the main state of the atom in the lowest energy levels.

3. The principle of the amount (number) of electrons in the shells, according to which the limit number of electrons in the shell may not exceed 2n 2, where N is the main quantum number of this shell. If the number of electrons in some shell reaches the limit value, the shell turns out to be filled and in the following elements, a new electronic shell begins to form.

In accordance with what was said, the table below gives: 1) the letter notation of the electronic shells; 2) the corresponding values \u200b\u200bof the main and side quantum numbers; 3) symbols of subgroups; 4) The theoretically calculated largest number of electrons in some subgroups and in the shells in general. It is necessary to indicate that in the shells K, L and M, the number of electrons and their distribution according to subgroups, determined from the experience, are quite associated with theoretical calculations, but significant differences are observed in the following shells: the number of electrons in the subgroup F reaches the limit value only in the shell N, in The next shell decreases, and then disappears the entire subgroup f.

Shell

Subgroup

The number of electrons in the subgroup

The number of electrons in the shell (2N 2)

The table gives the number of electrons in the shells and their distribution according to subgroups for all chemical elements, including transuranov. The numeric data of this table was established as a result of very thorough spectroscopic studies.

1st period
2nd period
3rd period
4th period
5th period
6th period
7th period

_______________

Sourse of information:Short physico-technical reference / volume 1, M.: 1960.

Electrons are distributed according to a certain form around the kernel, this distribution depends on the number of their energies, that is, the closer the electron to the nucleus of the atom, the less its amount of energy.

The electrons tend to take a position corresponding to the minimum energy value, and are located around the kernel according to the principle of Pauli. As is known from the previous topics, the largest number of electrons that can be located in each electron layer is determined by the formula N \u003d 2N 2. The first electron layer or layer K is on the closest distance from the nucleus of the atom and has n \u003d 1. In accordance with this, N \u003d 2-1 2 \u003d 2 electron moves on this layer. On the second electron layer can accommodate 8, on the third - 18, and on the fourth - 32 electrons.

In the outer electronic layers of all elements (except for elements 1 of the period) there are no more than eight electrons. External electronic layers of inert gases (with the exception of helium) are filled with eight electrons, so these gases are chemically stable.

At the external energy level of the elements of the main subgroup of the periodic table, the number of electrons is equal to the number of the group. The number of electrons in the outer layer of the elements of the side subgroup does not exceed two, during the transition from one element to the second, the attractive electrons move from the outer layer into the inner, since the external is replenished with NS 2 · NP 6 electrons, and the attachment electrons occupy the ND sublayer.

Thus, the manganese atom has the following structure: Mn (+25) 2, 8, 13, 2, and its electronic formula: 1S 2 · 2S 2 · 2P 6 · 3S 2 · 3P 6 · 3D 5 · 4S 2.

According to the principle of Pauli, in any atom there can not be two electrons with the same quantum numbers.

Consequently, on each orbital atom, the value of three quantum numbers - n, l, m (main, orbital and magnetic) may be the same, but the spin quantum numbers (s) differ, that is, there are electrons with opposite spins.

Replenishment of sublayer electrons was clarified with the help of the rules of V.M. Clekkovsky (1900-1972) according to which the electrons fill the energy slips in the following order:

The order of filling the cells (cells) of the energetic levels by electrons is obeyed by the rule of Hund. First, the cells are filling 2p are occupied by six electrons. The next electron, according to the rule of Klekkovsky, is moving into the energy sublayer 3s:

19. Clekkovsky rule Person:

The N + L rule was proposed in 1936 by the German physicist E. Madunung; In 1951, V. M. Klechkovsky was again formulated.

The electronic shell of the atom is the area of \u200b\u200bthe space of the likely location of electrons characterized by the same value of the main quantum number N and, as a result, located in close energy levels. The number of electrons in each electron shell does not exceed a certain maximum value.

The procedure for filling the electronic shells (orbitalings with the same value of the main quantum number N) is determined by the rule of the clerk, the order of filling the electrons of orbitals within the same sublevel (orbitals with the same values \u200b\u200bof the main quantum number N and the orbital quantum numerical) is determined by the Hund rule.

20.Atomic kernel - The central part of the atom in which its main mass is concentrated (more than 99.9%). The kernel is charged positively, the charge of the nucleus determines the chemical element to which the atom belongs. The sizes of the nuclei of various atoms constitute several femometrs, which is more than 10 thousand times less than the size of the atom itself.

The atomic core consists of nucleons - positively charged protons and neutral neutrons, which are interconnected by means of strong interaction

The number of protons in the kernel is called its charge number - this number is equal to the sequence number of the element to which the atom refers in the table (periodic system of elements) of Mendeleev. The number of protons in the nucleus determines the structure-electron shell of the neutral atom and, thus, the chemical properties of the corresponding element. The number of neutrons in the kernel is called its isotopic number. The kernels with the same number of protons and different numbers of neutrons are called exhibition. The kernel with the same number of neutrons, but different number of protons - are called isotones. The terms of isotope and isotone are also used as applied to atoms containing the specified kernels, as well as to characterize the non-smoked varieties of one chemical element. The total number of nucleons in the kernel is called its mass number () and approximately equal to the average mass of the atom indicated in the Mendeleev table. Nuclides with the same massive number, but by different proton-neutron composition it is customary to call by isobami.

Nuclear reaction - The process of converting atomic nuclei, occurring when they interact with elementary particles, gamma quanta and with each other. The nuclear reaction is the process of interaction of the atomic nucleus with another nucleus or an elementary particle, accompanied by a change in the composition and structure of the nucleus and the separation of secondary particles or γ-quanta. For the first time, the nuclear reaction was observed Rutherford in 1919, bombarding α-particles of nucleus atoms of nitrogen, it was recorded by the emergence of secondary ionizing particles having a gas mileage greater than the α-particles and identified as protons. Subsequently, with the help of the Wilson cameras, photos of this process were obtained.

According to the mechanism of interaction, nuclear reactions are divided into two types:

· Reaction with the formation of a composite nucleus, this is a two-stage process that occurs with not very large kinetic energy particles (approximately 10 MeV).

· Straight nuclear reactions passing through the nuclear time required for the particle crossed the kernel. Mainly, such a mechanism is manifested at high energies of bombarding particles.

Only a small part of the nuclides are stable. In most cases, nuclear forces are unable to ensure their constant integrity, and the nuclei is early or later disintegrated. This phenomenon got the name of radioactivity.

Radioactivity

Radioactivity is called the ability of the atomic nucleus to spontaneously disintegrate with the emission of particles. The radioactive decay is characterized by the time of life of radioactive isotope, the type of particles emitted, their energies.
The main types of radioactive decay are:

• α-decay - emission of the atomic core of the α particle;
• β-decay is the emission of an electron and antineutrino, positron and neutrino, the absorption of the nucleus of the atomic electron with the emission of neutrino;
• γ-decay - emission of the atomic core of γ-quanta;

· Spontaneous division - the decay of the atomic nucleus for two fragments of comparable mass.

21. Periodic system and periodic law by the beginning of the XIX century. About 30 elements were known, by the middle of the XIX V.- about 60. On the sea of \u200b\u200baccumulation of elements, the task of their systematization arose. Such attempts to D.I. Mendeleev was at least fifty; The basis of the systematization was taken: and atomic weight (now called atomic mass), and chemical equivalent, and valence. Approaching the classification of chemical elements, metaphysically, trying to systematize only known elements at that time, none of the predecessors of D. I. Mendeleev could open the universal interconnection of the elements, to create a single slender system reflecting the law of matter development. This important, for science, the task was brilliantly permitted in 1869 by the Grand Russian scientist D. I. Mendeleev, who discovered the periodical law.
The basis of the systematization of Mendeleev was taken: a) atomic weight and b) chemical resemblance between the elements. The most striking, the expressive similarity of the properties of elements is their equal higher valence. Both atomic weight (atomic weight) and the highest valence of the element are quantitative, numerical constants, convenient for systematization.
By placing everything known at that time, 63 elements in a row ascending atomic masses, Mendeleev noticed periodic repeatability of the properties of the elements through the unequal intervals. As a result, the Mendeleev was created the first version of the periodic system.
The legitimate nature of the changes in the atomic masses of elements on verticals and horizontals of the table, as well as empty MeCTs that formed in it allowed Mendeleev to boldly predict the native of a number of elements that are not yet known at that time science and even outline their atomic masses and basic properties based on the alleged position Elements in the table. This can be broken only on the basis of the system, objectively reflecting the law of the development of matter. The essence of the Periodic Law D. I. Mendeleev formulated in 1869: "The properties of simple bodies, as well as the forms and properties of the compounds of elements, are in periodic dependence on the value of atomic weights (mass) of the elements.

The design of the modern periodic system is in principle a little different from the version 1871. Symbols of elements in the periodic system are located along vertical and horizontal graphs. This leads to unification of elements in groups, subgroups, periods. Each element takes a specific cell in the table. Vertical graphs are groups (and subgroups), horizontal - periods (and rows).

Covalent communication

Communication arising from the interaction of electrons with the formation of generalized electronic pairs is called covalent.

If the interacting atoms have equal values \u200b\u200bof electronegativity, the total electron pair equally belongs to both atoms, that is, is at an equal distance from both atoms. Such a covalent connection is called notolar. It takes place in simple nonmetallah substances: H22, O22, N22, CL22, P44, O33.

When the interaction of atoms having different electronegability values, for example, hydrogen and chlorine, the total electron pair turns out to be displaced in the direction of the atom with greater electronegitability, that is, in the direction of chlorine.

The chlorine atom acquires a partial negative charge, and the hydrogen atom is a partial positive. That's an example polar covalent bond.

Covalent bond properties

The characteristic properties of a covalent bond - orientation, saturation, polarity, polarizability - determine the chemical and physical properties of organic compounds.

Focusingdetermines the molecular structure of organic substances and the geometric shape of their molecules. Corners between two connections are called valence.

Saturability - the ability of atoms to form a limited number of covalent bonds. The number of connections formed by an atom is limited by the number of its external atomic orbitals.

The polarity of the communication is due to the uneven distribution of electron density due to differences in the electrical negativeness of atoms. On this basis, covalent ties are divided into non-polar and polar.

The polarizability of communication is expressed in the displacement of electrons of communication under the influence of an external electric field, including another reacting particle. Polarizability is determined by electron mobility. Electrographs are more moving, the further they are from the nuclei.

The polarity and polarizability of covalent bonds determines the reactivity of molecules with respect to polar reagents.

23. ion communications - Chemical bonds formed between atoms with large difference in electrical negativeness, in which the general electron pair fully moves to the atom with greater electronegitability.
Since the ion can attract the ions of the opposite sign in any direction, the ion connection from covalent is distinguished by non-directivity.

The interaction with each other of two ions of the opposite sign cannot lead to a complete mutual compensation for their strength fields. Therefore, they can attract other ions of the opposite sign, that is, an ion connection is distattable.

24. Metal communication - chemical bond between atoms in a metallic crystal, which arises due to the generalization of their valence electrons.

Metal communication- The relationship between positive ions in metals crystals, carried out by attracting electrons freely moving along the crystal. In accordance with the position in the periodic system, the metals atoms have a small number of valence electrons. These electrons are rather poorly connected with their cores and can easily break away from them. As a result, positively charged ions and free electrons appear in the crystal lattice of the metal. Therefore, in the crystal lattice of metals there is a great freedom of movement of electrons: one of the atoms will lose their electrons, and the resulting ions can take these electrons from the "electronic gas". As a result, the metal is a number of positive ions localized in certain positions of the crystal lattice, and a large number of electrons that are relatively freely moving in the field of positive centers. This is an important difference between metal ties from covalent, which have a strict orientation in space.

Metal bond differs from covalent, also by strength: its energy is 3-4 times less than the energy of a covalent bond.

Hydrogen communications

The hydrogen atom connected to the fluorine, oxygen or nitrogen atom (less often - chlorine, sulfur or other non-metals), can form another additional connection. This discovery made in the eighties of the nineteenth century, is associated with the names of Russian chemists M.A. Ilyinsky and N.N. Beketova. It was found that some hydrogen-containing groups of atoms often form a steady chemical bond with electronegative atoms that are part of another or the same molecule. Such a chemical relationship received the name of the hydrogen bond.

The hydrogen bond is the interaction between two electronegative atoms of one or different molecules by means of a hydrogen atom: A-N ... in (a covalent bond is indicated, three points - hydrogen bond).

The hydrogen bond is due to the electrostatic attraction of the hydrogen atom (carrier charge δ +) to an electro-negative element atom that has a negative charge Δ-. In most cases, it is weaker than covalent, but significantly stronger than the usual attraction of molecules to each other in solid and liquid substances. In contrast to intermolecular interactions, hydrogen bonds has the properties of the orientation and saturation, therefore it is often considered one of the types of covalent chemical bond. It can be described using the method of molecular orbitals as a three-centride-unionelectronic connection.

One of the signs of the hydrogen bond can be the distance between the hydrogen atom and the other atom, it formes. It should be less than the sum of the radii of these atoms. More often there are asymmetric hydrogen bonds, in which the distance H ... in more than A-B. However, in rare cases (fluorine hydrogen, some carboxylic acids), hydrogen bond is symmetric. The angle between the atoms in the Fragment A-H ... is usually close to 180 o. The strongest hydrogen bonds are formed with the participation of fluorine atoms. In a symmetric ion - the hydrogen bond energy is 155 kJ / mol and comparable to the covalent bond energy. The energy of hydrogen bonds between water molecules is already noticeably less (25 kJ / mol).

26. Thermal effect of the chemical reaction Or a change in the enthalpy of the system due to the flow of a chemical reaction - the amount of heat obtained by the system obtained to the chemical variable, which passed the chemical reaction and the reaction products took the reagent temperature.

In order for the thermal effect to be the value depending only on the nature of the underlying chemical reaction, compliance with the following conditions:

· The reaction should proceed either at a constant amount of Q V (isochoric process), or at a constant pressure of Q P (isobaric process).

· No work is performed in the system, apart from P \u003d const expansion operation.

If the reaction is carried out under standard conditions at T \u003d 298.15 K \u003d 25 ˚С and P \u003d 1 atm \u003d 101325 Pa, the thermal effect is called the standard thermal effect of the reaction or standard enthalpy of the reaction ΔH R O. In thermochemistry, the standard thermal effect of the reaction is calculated using standard enthalpies of education.

GESS Act (1841)

The thermal effect (enthalpy) of the process depends only on the initial and end state and does not depend on the path of transition from one state to another.

28. Chemical reaction rate - change in the number of one of the reacting substances per unit of time per unit of reaction space. It is the key concept of chemical kinetics. The speed of the chemical reaction is always positive, therefore, if it is determined by the source substance (the concentration of which decreases during the reaction process), then the obtained value is multiplied by -1.

In 1865, N. N. Beketov and in 1867, Guldberg and Vaage was formulated by the law of the active masses: the rate of chemical reaction at each moment of time is proportional to the concentrations of reagents, erected to the degree equal to their stoichiometric coefficients

For elementary reactions, the indicator of the degree with the value of the concentration of each substance is often equal to its stoichiometric coefficient, for complex reactions this rule is not respected. In addition to the concentration on the rate of chemical reaction, the following factors affect:

· The nature of the reactant substances

· The presence of a catalyst,

· Temperature (Vant-Gooff rule, Arrhenius equation),

· Pressure,

· The surface area of \u200b\u200bthe reactant substances.

If we consider the simplest chemical reaction A + B → C, then we note that the instantaneous speed of the chemical reaction is non-permanent

29.Arts.In 1865, Professor N.N. Beketov first expressed the hypothesis about the quantitative relationship between the masses of reagents and the reaction time. This hypothesis found confirmation in the law of the existing masses, which was established in 1867 by two Norwegian chemists K. Guldberg and P. Vaiga. Modern formulation of the law of the current masses is:

At a constant temperature, the rate of the chemical reaction is directly proportional to the product of the concentrations of reacting substances taken in degrees equal to stoichiometric coefficients in the reaction equation.

Periodic system of Mendeleev elements.

Periodic system of chemical elements (mendeleev table) - Classification of chemical elements, which establishes the dependence of the various properties of the elements from the charge of the atomic kernel.

Groups

A group, or a family, is one of the speakers of the periodic table. For groups, as a rule, more substantially pronounced periodic trends are characterized than for periods or blocks.

In accordance with the international naming system, groups are assigned numbers from 1 to 18 in the direction from left to right - from alkaline metals to noble gases.

Periods

Period - line of the periodic table. In the period of the period, elements demonstrate certain patterns in all three above-mentioned aspects (atomic radius, the energy of the ionization of melectricity monitance), as well as in the energy of the electron affinity.

Blocks

Due to the significance of the external electronic shell of an atom, various areas of the periodic table are sometimes described as blocks, called in accordance with what shell is the last electron. The S-block includes the first two groups, that is, alkaline and alkaline earth metals, as well as hydrogen and helium; The P-block consists of the last six groups (from 13 to 18 according to the Naming Standard of the Jew, or from IIIa to VIIIA on the American system) and includes, in addition to other elements, all metalloids. The D-block is groups from 3 to 12 (Jouple), they are also with IIIB to IIB an American, which includes all transition metals. The F-block, usually ended outside the table, consists of lanthanides and actinoids.

Periodic System D. I. Mendeleev became the most important milestone in the development of atomic molecular teachings. Thanks to her, the contemporary concept of the chemical element was developed, the ideas about ordinary substances and connections were clarified.

The composition and characteristics of the atomic nucleus.

Atomic kernel - The central part of the atom in which its main mass is concentrated (more than 99.9%). The kernel is charged positively, the charge of the nucleus determines the chemical element to which the atom belongs.

The atomic core consists of nucleons - positively charged protons and neutral neutrons that are interconnected by means of strong interaction.

The atomic kernel, considered as a class of particles with a certain number of protons and neutrons, is customary called nuclide.

The number of protons in the kernel is called its charge number - this number is equal to the sequence number of the element to which the atom refers in the table (periodic system of elements) of Mendeleev. The number of protons in the nucleus determines the structure of the electronic shell of the neutral atom and, thus, the chemical properties of the corresponding element. The number of neutrons in the kernel is called it isotopic number . The kernels with the same number of protons and different numbers of neutrons are called isotopes. The kernel with the same number of neutrons, but different number of protons - are called isotones.

The total number of nucleons in the kernel is called its mass number () and approximately equal to the average mass of the atom indicated in the Mendeleev table. Nuclides with the same massive number, but by different proton-neutron composition it is customary to call by isobami.

Weight

Due to the difference among neutrons, the isotopes of the element have a different mass, which is an important characteristic of the kernel. In nuclear physics, the mass of the nuclei is made to measure in atomic units of the mass ( but. eat.), for one a. e. m. Take 1/12 part of the mass of nuclide 12 C [CH 2]. It should be noted that the standard mass, which is usually given for nuclide, is the mass of a neutral atom. To determine the mass of the nucleus, it is necessary to calculate the sum of the masses of all electrons from the mass of the atom (the more accurate value is, if you also consider the electron communication energy with the kernel).

In addition, the energy equivalent of the masses is often used in nuclear physics. According to the ratio of Einstein, the total energy corresponds to each mass value:

Where is the speed of light in vacuum.

The ratio between a. e. m. and its energy equivalent in Joules:

and since 1 electronof \u003d 1,602176 · 10 -19 J, the energy equivalent A. e. m. MeV is equal

Radius

An analysis of the collapse of heavy cores clarified the assessment of Rangeford [CH 3] and connected the radius of the kernel with a massive number by a simple ratio:

where is the constant.

Since the radius of the nucleus is not a purely geometric characteristic and is primarily associated with the radius of the actions of nuclear forces, the value depends on the process, when analyzing which the value was obtained, the average value of M, so the kernel radius in meters

Charge

The proton number in the kernel determines its electrical charge directly, the isotopes have the same number of protons, but a different amount of neutrons. .

For the first time, the charges of atomic nuclei identified Henry Cosli in 1913. The scientist interpreted his experimental observations by the dependence of the X-ray wavelength from a certain constant varying per unit from the element to the element and equal unit for hydrogen:

where

And - permanent.

Nuclear communication energy.

The core binding energy is minimal energy that needs to be expensive to complete the kernel splitting into separate particles. From the law of conservation of energy it follows that the bond energy is equal to the energy that is allocated during the formation of the nucleus from individual particles.

The binding energy of any nucleus can be determined using accurate measurement of its mass. Currently, physicists have learned to measure the masses of particles - electrons, protons, neutrons, nuclei, etc. - with very high accuracy. These measurements show that mass of any nucleus M. I always have less than the sum of the masses of the protons and neutrons:

This energy is released during the formation of the kernel in the form of radiation of γ-quanta.

Nuclear power.

Nuclear power are short-range Forces. They are manifested only on very low distances between nucleons in the kernel of about 10 -15 m. Length (1.5 - 2.2) · 10 -15 m is called radius of the actions of nuclear forces.

Nuclear forces are detected charging independence : Attraction between two nucleons is equally independent of the charge state of the nucleons - proton or neutron. The charge independence of nuclear forces is visible from comparison of communication energies mirror kernels . So called nuclei, in which the same overall number of nucleons, But the number of protons in one is equal to the number of neutrons by another.

Nuclear power possess property saturation , which manifests itself in, that the nucleon in the kernel interacts only with a limited number of neighboring nucleons closest to it. That is why there is a linear dependence of the energies of the nuclear communication from their mass numbers A.. Practically complete saturation of nuclear forces is achieved in the α particle, which is very sustainable education.

Nuclear forces depend on orientation of spins interacting nucleons. This is confirmed by the different nature of neutron scattering by ortho and parasodorodore molecules. In the molecule of the orthodorod of the back of both protons are parallel to each other, and in the molecule of the paraguodor, they are anti-parallel. Experiments have shown that the scattering of neutrons on a parachodode is 30 times the scattering on the orthoder plant. Nuclear forces are not central.

So, list general properties of nuclear forces :

· Small radius of the actions of nuclear forces ( R. ~ 1 fm);

· Great nuclear potential U. ~ 50 MeV;

· The dependence of nuclear forces from spins of interacting particles;

· The tensor nature of the interaction of nucleons;

· Nuclear forces depend on the mutual orientation of the spin and orbital moments of nucleon (spin-orbital forces);

· Nuclear interaction has the property of saturation;

· Charge independence of nuclear forces;

· The overall nature of nuclear interaction;

· Attraction between nucleons at large distances ( r. \u003e 1 FM), replaced by repellent on small ( r. < 0,5 Фм).

The distribution of electrons by energy levels explains the metallic, as well as the non-metallic properties of any elements.

Electronic formula

There is a specific rule, according to which free and paired negative particles are placed at levels and sublevels. Consider in more detail the distribution of electrons by energy levels.

At the first energy level there are only two electrons. The filling of them orbital is carried out as the stock of energy increases. The distribution of electrons in the chemical element atom corresponds to the sequence number. Energy levels with a minimum number are maximally expressed the force of attraction of valence electrons to the kernel.

An example of electronic formula

Consider the distribution of electrons by energy levels on the example of the carbon atom. Its sequence number 6, therefore, inside the nucleus is six protons that have a positive charge. Given that carbon is a representative of the second period, it is characterized by the presence of two energy levels. On the first there are two electrons, on the second - four.

The Hinda rule explains the location in one cell only two electrons that have different backs. At the second energy level there are four electrons. As a result, the distribution of electrons in the atom of the chemical element has the following form: 1S22S22P2.

There are certain rules according to which the distribution of electrons by sublayers and levels occurs.

Powli principle

This principle was formulated by Pauli in 1925. The scientist stated the possibility of placing in the atom only two electrons, which have the same quantum numbers: n, l, m, s. Note that the distribution of electrons by energy levels occurs as the reserve of free energy increases.

Clekkovsky rule

The filling of energy orbitals is carried out according to an increase in quantum numbers N + L and is characterized by an increase in the energy reserve.

Consider the distribution of electrons in the calcium atom.

In the normal state, its electronic formula has the following form:

CA 1S2 2S2 2P6 3S2 3P6 3D0 4S2.

The elements of such subgroups relating to D- and F-elements are observed a "failure" of an electron from an external suberring, which has a smaller energy supply, on the previous D-or F-subline. This phenomenon is characteristic of copper, silver, platinum, gold.

The distribution of electrons in the atom involves filling with suddenly unpaired electrons, which possess the same spins.

Only after full filling of all free orbitals with single electrons, there is an addition to the quantum cells by the second negative particles endowed with opposite spins.

For example, in an unexcited state of nitrogen:

The properties of substances affect the electronic configuration of valence electrons. By their number it is possible to determine the highest and lower valence, chemical activity. If the element is in the main subgroup of the Mendeleev table, it is possible to make an external energy level by the number of the group, determine its degree of oxidation. For example, phosphorus, which is in the fifth group (the main subgroup), contains five valence electrons, therefore, it is able to take three electrons or give five particles to another atom.

As exceptions, all representatives of side subgroups of the Mendeleev table are acting as exceptions.

Features of families

Depending on how the structure has an external energy level, there is a division of all neutral atoms included in the Mendeleev table for four families:

• s-elements are in the first and second groups (main subgroups);
• the P-family is located in III-VIII groups (and subgroups);
• d-elements can be found in similar subgroups from the I-VIII group;
• the F-family makes actinoids and lanthanoids.

All S-elements are in good condition there are valence electrons on S-supro. For p-elements, the presence of free electrons on S- and p-suits.

In the D-elements in an unexcited state there are valence electrons and on the last S-, and in the penultimate D- paragraph.

Conclusion

The state of any electron in the atom can be described using a set of basic numbers. Depending on the features of its structure, it is possible to talk about a certain stock of energy. Using the Rule of Hund, Clekkovsky, Pauli for any element included in the Mendeleev table, you can make a configuration of a neutral atom.

Electrons located at the first level have the most incompetent energy reserve. When the neutral atom is heated, the transition of electrons is observed, which is always accompanied by a change in the number of free electrons, leads to a significant change in the indicator of the degree of oxidation of the element, the change in its chemical activity.

The distribution of electrons by energy levels explains the metallic, as well as the non-metallic properties of any elements.

Electronic formula

There is a specific rule, according to which free and paired negative particles are placed at levels and sublevels. Consider in more detail the distribution of electrons by energy levels.
At the first energy level there are only two electrons. The filling of them orbital is carried out as the stock of energy increases. The distribution of electrons in the chemical element atom corresponds to the sequence number. Energy levels with a minimum number are maximally expressed the force of attraction of valence electrons to the kernel.

An example of electronic formula

Consider the distribution of electrons by energy levels on the example of the carbon atom. Its sequence number 6, therefore, inside the nucleus is six protons that have a positive charge. Given that carbon is a representative of the second period, it is characterized by the presence of two energy levels. On the first there are two electrons, on the second - four.
The Hinda rule explains the location in one cell only two electrons that have different backs. At the second energy level there are four electrons. As a result, the distribution of electrons in the atom of the chemical element has the following form: 1S22S22P2.
There are certain rules according to which the distribution of electrons by sublayers and levels occurs.

Powli principle

This principle was formulated by Pauli in 1925. The scientist stated the possibility of placing in the atom only two electrons, which have the same quantum numbers: n, l, m, s. Note that the distribution of electrons by energy levels occurs as the reserve of free energy increases.

Clekkovsky rule

The filling of energy orbitals is carried out according to an increase in quantum numbers N + L and is characterized by an increase in the energy reserve.
Consider the distribution of electrons in the calcium atom.
In the normal state, its electronic formula has the following form:
CA 1S2 2S2 2P6 3S2 3P6 3D0 4S2.
The elements of such subgroups relating to D- and F-elements are observed a "failure" of an electron from an external suberring, which has a smaller energy supply, on the previous D-or F-subline. This phenomenon is characteristic of copper, silver, platinum, gold.
The distribution of electrons in the atom involves filling with suddenly unpaired electrons, which possess the same spins.
Only after full filling of all free orbitals with single electrons, there is an addition to the quantum cells by the second negative particles endowed with opposite spins.
For example, in an unexcited state of nitrogen:
1S2 2S2 2p3.
The properties of substances affect the electronic configuration of valence electrons. By their number it is possible to determine the highest and lower valence, chemical activity. If the element is in the main subgroup of the Mendeleev table, it is possible to make an external energy level by the number of the group, determine its degree of oxidation. For example, phosphorus, which is in the fifth group (the main subgroup), contains five valence electrons, therefore, it is able to take three electrons or give five particles to another atom.
As exceptions, all representatives of side subgroups of the Mendeleev table are acting as exceptions.

Features of families

Depending on how the structure has an external energy level, there is a division of all neutral atoms included in the Mendeleev table for four families:

s-elements are located in the first and second groups (main subgroups); The P-family is located in III-VIII groups (and subgroups); D-elements can be found in similar subgroups from the I-VIII group; the F-family makes actinoids and lantanoids.

All S-elements are in good condition there are valence electrons on S-supro. For p-elements, the presence of free electrons on S- and p-suits.
In the D-elements in an unexcited state there are valence electrons and on the last S-, and in the penultimate D- paragraph.

Conclusion

The state of any electron in the atom can be described using a set of basic numbers. Depending on the features of its structure, it is possible to talk about a certain stock of energy. Using the Rule of Hund, Clekkovsky, Pauli for any element included in the Mendeleev table, you can make a configuration of a neutral atom.
Electrons located at the first level have the most incompetent energy reserve. When the neutral atom is heated, the transition of electrons is observed, which is always accompanied by a change in the number of free electrons, leads to a significant change in the indicator of the degree of oxidation of the element, the change in its chemical activity.