Electron distribution rules for energy levels. The distribution of electrons according to the energy levels of the atom. An example of electronic formula

Each electron in the atom moves in the first approximation in the central symmetric non-fladion field of the electron in this case is determined by three quantum numbers, the physical meaning of which was found in § 28. Due to the existence of the electron spin to the specified quantum numbers, add a quantum number that can take Values \u200b\u200band defines the projection of the back to the specified direction. In the future, for a magnetic quantum number, we will instead of using the designation to emphasize that this number determines the projection of the orbital moment, the value of which is given by the quantum number L.

Thus, the state of each electron in the atom is characterized by four quantum numbers:

The energy of the state depends mainly from numbers.

In addition, there is a weak energy dependence on numbers since their values \u200b\u200bare associated with the mutual orientation of the moments on which the magnitude of the interaction between the orbital and its own magnetic moments of the electron depends. The state of the state increases with an increase in the number than with an increase there is therefore, as a rule, a state with a large has, regardless of the value of greater energy.

In a normal (unexcited) state of an atom, the electrons should be located on the lowest energy levels available for them. Therefore, it would seem, in any atom in normal condition, all electrons should be able to be in a state and the main terms of all atoms should be like -Terms However, experience shows that it is not.

The explanation of the observed types of terms is as follows. According to one of the laws of quantum mechanics, called Powli principle, in the same atom (or in any other quantum system) cannot be two electrons with the same set of quantum numbers. In other words, in the same state there can be simultaneously two electrons.

In § 28 it was shown that this corresponds to the states characterized by the values \u200b\u200bl and the quantum number can take two values: therefore, in states with this value, no more electrons may be in the atom:

The combination of electrons having the same values \u200b\u200bof the quantum number forms a shell. The shells are divided into submarines, characterized by the value of the quantum number L. In accordance with the value of the shells, there are notation borrowed from X-ray spectroscopy:

Table 36.1.

The division of possible states of the electron in the atom on the shell and submarine is shown in Table. 36.1, in which instead of designations apply for clarity symbols :. The submarine, as indicated in the table, can be designated in two ways (for example, either).

Theme of the lesson: "The distribution of electrons by atomic orbitals"

Purpose: study the distribution of electrons by orbital

Developing: Development of logical thinking by means of establishing causal relationships.

Educational: to study such concepts as: electronic cloud, orbital, nuclear orbital, form of existence of orbital, orbital filling rules.

The position of the element in the periodic table causes its properties, the sequence number shows the charge of the nucleus of the atom, the number of the energy level period, the number of the electron number in the last energy level.

Electrons are distributed around the kernel in energy levels and move according to certain nuclear orbital.

Atomic orbital is the area of \u200b\u200bthe most likely to stay of the electron in the electrical field of the nucleus of the atom

The position of the element in the PS determines the type of its orbitals differing in the form, sizes

s-orbital

p- orbital

d- orbital

for the elements of the first period, one ES Orbital is characterized, elements 2 of the period to ES orbitals are added to the orbital, the elements of the period 3 appears D

The order of filling the levels and sublayer electrons.

I. Electronic formulas of atoms of chemical elements are in the following order:

· Determine by the element number in Table D. I. Mendeleev, the total number of electrons in the atom;

· By the number of the period, it is necessary to determine the number of energy levels;

· Levels are divided into sublevels and orbital, and filled with electrons in accordance The principle of least energy

· For convenience, the electrons can be distributed according to energy levels, using the formula n \u003d 2N2 and taking into account the fact that:

1. At the elements major subgroups (S-; P-elements) The number of electrons at the external level is equal to the number of the group.

2. Elements side subgroups at the external level usually two Electron (exceptions are atoms Cu, AG, AU, CR, NB, MO, RU, RHwho are at the external level one Electron, U. Pd. At the external level zero electrons);

3. The number of electrons in the penultimate level is equal to the total number of electrons in the atom minus the number of electrons at all other levels.

II. The order of filling by electrons of atomic orbitals is determined:

1. Dropsip the lowest energy

Energie scale:

III. Family chemical elements.

Elements in the atoms of which are filling with electrons S-supro external s-elements. This is the first 2 Element of each period constituting the main subgroups I. and II. Group.

Elements in the atoms of which the P-sublayer is filled with electrons external energy level called p-elements. This is the latter 6 elements of each period (except I. and VII) constituting the main subgroups III-VIII. Group.

Elements that are filled with D-supro second outside the level called d-elements. These are elements of plug-in decades IV, V, VI periods.

Elements in which f-supel is filled third outside the level called f-elements. F-elements include lanthanoids and actinoids.

Since the chemical reactions of the core of the reactant atoms remain unchanged, the chemical properties of atoms depend primarily on the structure of the electronic shells of atoms. Therefore, we will discuss in more detail on the distribution of electrons in the atom and mainly those that cause the chemical properties of atoms (the so-called valence electrons), and consequently, the frequency in the properties of atoms and their compounds. We already know that the state of the electrons can be described by a set of four quantum numbers, but to explain the structure of the electronic shells of atoms, another three of the following basic provisions are needed: 1) the principle of Pauli, 2) the principle of the lowest energy and 3) struck Gund. Principle Pauli. In 1925, the Swiss physicist V. Pauli established the rule called by the principle of Pauli (or Paul's ban): in the atom there may be two electrons with the same outbreak & mi. Knowing that the properties of electrons are characterized by quantum numbers, the principle of Pauli can be formulated and thus: in the atom there can be no two electrons, in which all four quantum numbers would be the same. At least one of the quantum numbers l, /, mt or T3 should be different. Thus, the electrons with the same kwan- in the future we consider graphically signify the electrons having the values \u200b\u200bs \u003d + lj2\u003e the arrow T, and having the values \u200b\u200bof J- ~ LF2 - the two electrons with the same backs, which have the same backs, are often referred to as electrons with parallel spins N denotes ft (or C). Two electrons with opposite backs are called electron with apotipallated spins N denotes | J- The L, I and MT numbers should necessarily differ by the backs. Therefore, in the atom there can be only two aircraft with the same L, / and T, \\ one with T, \u003d -1/2, another with TM \u003d + 1/2. On the contrary, if the backs of two electrons are the same, one of the quantum numbers should be different: p, / or Mh knowing the principle of Pauli, let's see how many electrons in the atom can be on a certain "orbit" with the main quantum number of the first "orbit" corresponds to P \u003d 1. Then / \u003d 0, MT-0 and TL may have an arbitrary value: +1/2 or -1/2. We see that if P-1, there can be only two of such electrons. In general, with any given value of L, the electrons are primarily different by a bypass quantum number / receiving values \u200b\u200bfrom 0 to L-1. For whether it is set / may, BGGG (2 / + 1) electrons with different values \u200b\u200bof the magnetic quantum number T ,. This number must be doubled, since the specified values \u200b\u200bof L, / and T (two different values \u200b\u200bof the projection of the spin TX correspond to. Therefore, the maximum number of electrons with the same quantum number of l is expressed by the amount from here, why there may be no more than 2 electrons at the first energy level, on the second - 8, in the third - 18, etc. Consider, for example, hydrogen atom IH. In the hydrogen atom, IH has one electron, and the spin of this electron can be directed arbitrarily (i.e. MS ^ + IJ2 or MT \u003d -1 / 2), and the electron is located in the S-CO standing at the first energy level with L-1 (Recall once again that the first energy level consists of a single sublevel - 15, the second energy level is from two sublevels - 2s and 2r, the third is of three sublevels - 3 *, 3D ZPA, etc.). The sublevel, in turn, is divided into quantum cells * (energy states determined by the number of possible values \u200b\u200bof T (, that is, 2/4-1). The cell is taken graphically to depict the rectangle, the direction of the electron spin - arrows. Therefore, the state of the electron in the atom IH hydrogen can be represented as ijt1, or the same, under the "quantum cell" imply * orbital, characterized by the same set of values \u200b\u200bof quantum numbers P, I and T * in each cell, a maximum of two electrons with asti-parallel spins can be placed, which is indicated by Ti - distribution of electrons in atoms in the helium atom 2No quantum numbers P-1, / \u003d 0, and T (-0 the same for both its electrons, and the quantum number T3 is different. Projections of the spin of helium electrons can be MT \u003d + V2 and MS \u003d - V2 . The structure of the electronic shell of the helium atom 2 should be represented as IS-2 or, which is the same, 1S and depict the structure of the electronic shells of the five atoms of the agents of the second period of the periodic table of Mendeleev: what email Extronic BS shells, 7N and should be filled out exactly that way is not obvious in advance. The reduced location of the spins is determined by the so-called rule of Gund (first formulated in 1927 by the German physicist F. Gong-house). Gund rule. With this value I (i.e., within a certain sublayer), electrons are arranged in such a way that the total hundred * is maximal. If, for example, in the three / ^ - cells of the nitrogen atom, it is necessary to distribute three electrons, then they will be located each in a separate cell, i.e. it is placed on three different p-or-bitals: in this case, the total spin is 3/2, Since its projection is equal to T3 - 4-1 / 2 + A / 2 + 1/2 \u003d 3/2 * The same three electrons cannot be arranged in this way: 2p is neither then the projection of the total spin TM \u003d +1/2 - 1/2 + + 1/2 \u003d 1/2. For this reason, it is exactly how the electrons in carbon atoms, nitrogen and oxygen are located above are. Consider further electronic configurations of atoms of the next third period. Starting with Sodium UNA, the third energy level with the main quantum number of P-3 is filled. Atoms of the first eight elements of the third period have the following electronic configurations: We now consider the electronic configuration of the first atom of the fourth period of potassium 19k. The first 18 electrons fill the following orbital: LS12S22P63S23P6. It would seem that; that the nineteenth electron of potassium atom should get to the 3D proro-Van, which corresponds to n \u003d 3 and 1 \u003d 2. However, in fact, the valence electron of the potassium atom is located on the orbital of 4S. Further filling of the shells after the 18th element occurs in such a sequence, as in the first two periods. Electrons in atoms are arranged in accordance with the principle of Pauli and the rule of Gund, but so that their energy is the smallest. The principle of the lowest energy (the domestic scientist V. M. Clachkov-cue) was the greatest contribution to the development of this principle) - in the atom, each electron is located so that its energy is minimal (which corresponds to its greatest connection with the nucleus). The electron energy is mainly determined by the main quantum number of P and a side quantum number /, therefore, those supers are filled first, for which the sum of the values \u200b\u200bof quantum numbers PI / is the smallest. For example, an electron energy on a superal 4S is less than on the 3D sublevel, since in the first case P + / \u003d 4 + 0 \u003d 4, and in the second p + / \u003d 3 + 2 \u003d 5; on superts 5 * (n + / \u003d 5 + 0 \u003d 5) energy is less than on ad (l + / \u003d 4 + 4-2 \u003d 6); on 5p (l + / \u003d 5 +1 \u003d 6) the energy is less than 4 / (l-f / \u003d 4 + 3 \u003d 7), etc. It was V. M. Klekkovsky for the first time in 1961 The general position has formulated that the electron is in the main state level not with the minimum possible value of P, but with the smallest value of the amount of l + / "when for two sublevels of the values \u200b\u200bof PI / equal values, the filling of a sublevel with a smaller value Clause, for example, on 3D, AR, 5S, the sum of the values \u200b\u200bof PI / equal to 5. In this case, the filling of sublevels with less values \u200b\u200bof l, i.e. 3DAP-5S, etc. In the periodic system of Mendeleev elements, the sequence of filling by electrons Levels and sublevels looks as follows (Fig. 2.4). Distribution of electrons in atoms. The power levels of energy levels and sublevels consequently, according to the principle of the lowest energy in many cases, the electron is energetically more profitable to occupy the sublayer "overlying" level, although the sublayer of the "underlying" level is not filled: that is why 4S sublee is filled in the fourth period and only after that 3D sublevel .

Electronic configuration Atom is a numerical representation of its electronic orbitals. Electronic orbitals are areas of different shapes located around the atomic nucleus in which the electron is mathematically likely. The electronic configuration helps to quickly and easily say to the reader, how many electronic orbitals have at the atom, as well as determine the number of electrons located on each orbital. After reading this article, you master the method of compiling electronic configurations.

Steps

The distribution of electrons with the help of the periodic system D. I. Mendeleev

Find the atomic number of your atom. Each atom has a certain number of electrons associated with it. Find a symbol of your atom in the Mendeleev table. Atomic number is an integer positive number, starting from 1 (in hydrogen) and increasingly increasingly at each subsequent atom. Atomic number is the number of protons in the atom, and, therefore, it is also the number of electrons of an atom with a zero charge.

Determine the atom charge. Neutral atoms will have as many electrons as shown in the Mendeleev table. However, the charged atoms will have a greater or smaller number of electrons - depending on the size of their charge. If you are working with a charged atom, add or subtract the electrons as follows: add one electron to each negative charge and subtract one to each positive.

• For example, a sodium atom with charge -1 will have an additional electron in addition To its base atomic number 11. In other words, in the amount of the atom there will be 12 electrons.
• If we are talking about the sodium atom with charge +1, from the base atomic number 11 you need to take one electron. Thus, at the atom will be 10 electrons.

1. Remember the basic list of orbital. As the atom increases the number of electrons, they fill various sublayers of an atom electronic shell according to a certain sequence. Each sublayer of the electronic shell, being filled, contains an even number of electrons. There are the following suggested:

   Observe the e-configuration record. Electronic configurations are recorded in order to clearly reflect the amount of electrons on each orbital. The orbitals are recorded in series, and the number of atoms in each orbital is written as the upper index to the right of the orbital name. Completed electronic configuration has a form of a sequence of reference and upper indexes.

   • For example, the simplest electronic configuration: 1S 2 2S 2 2p 6. This configuration shows that there are two electrons, two electron - on 2s and six electrons on the 2P 2p. 2 + 2 + 6 \u003d 10 electrons in sum. This is an electronic configuration of a neutral neon atom (Nuclear Nuclear Number - 10).

2. Remember the order of orbitals. Keep in mind that electronic orbitals are numbered in ascending order of the electronic shell number, but are located ascending energy. For example, the filled orbital 4S 2 has a lower energy (or less mobile) than partially filled or filled 3D 10, so the orbital 4S orbital is written. As soon as you know the order of orbitals, you can easily fill them in accordance with the number of electrons in the atom. The order of filling orbitals is as follows: 1S, 2S, 2P, 3S, 3P, 4S, 3D, 4P, 5S, 4D, 5P, 6S, 4F, 5D, 6P, 7S, 5F, 6D, 7P.

   • The electronic configuration of the atom in which all orbitals are filled, will have the following type: 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 3D 10 4P 6 5S 2 4D 10 5P 6 6S 2 4F 14 5D 10 6P 6 7S 2 5F 14 6D 10 7P 6.
   • Please note that the above recording when all orbitals are filled with the electronic configuration of the UUO element (shift) 118, the atom of the periodic system with the largest number. Therefore, this electronic configuration contains all the electronic references of a neutrally charged atom known in our time.

3. Fill orbital according to the number of electrons in your atom. For example, if we want to record the electronic configuration of the neutral calcium atom, we must start with the search for its atomic number in the Mendeleev table. Its atomic number is 20, so we will write the configuration of an atom with 20 electrons according to the above order.

   • Fill the orbital according to the above order until you reach the twentieth electron. On the first 1s orbitals there will be two electrons, 2s orbitals are also two, 2p - six, on 3S - two, 3p - 6, and 4S - 2 (2 + 2 + 6 +2 +6 + 2 \u003d 20 .) In other words, the electronic calcium configuration is: 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2.
   • Please note: orbitals are located in an increase in energy. For example, when you are ready to go to the 4th energy level, you first write 4s orbital, and then 3D. After the fourth energy level, you go to the fifth, on which the same order is repeated. This happens only after the third energy level.

4. Use the Mendeleev table as a visual tip. You probably have already noticed that the form of the periodic system corresponds to the order of electronic sublevels in electronic configurations. For example, atoms in the second column on the left always end on "S 2", and atoms on the right edge of the fine middle part ends on "D 10", etc. Use the periodic system as a visual guide to writing configurations - as an order, according to which you add to orbitals, matches your position in the table. See below:

   • In particular, the two most left columns contain atoms whose electronic configurations ends with S-orbital, in the right block of the table presents atoms, whose configurations are submitted by p-orbital, and at the bottom of the atoms end with F-orbitals.
   • For example, when you record the electronic chlorine configuration, reflect on the following way: "This atom is located in the third row (or" period ") of the Mendeleev table. It is also located in the fifth group of the orbital block P of the periodic system. Therefore, its electronic configuration will end on. ..3p 5.
   • Please note: elements in the orbital area D and F table are characterized by energy levels that do not correspond to the period in which they are located. For example, the first row of elements with D-orbital elements corresponds to 3D orbital, although it is located in 4 period, and the first row of elements with F-orbitals corresponds to the orbital 4F, despite the fact that it is in the 6th period.

5. Learn to reduce the writing of long electronic configurations. Atoms on the right edge of the periodic system are called noble gases. These elements are chemically very stable. To reduce the process of writing long electronic configurations, simply write in square brackets with a chemical symbol of the nearest noble gas with a smaller compared to your atom number of electrons, and then continue to write an electronic configuration of subsequent orbital levels. See below:

   • To understand this concept, it will be useful to write an example of a configuration. Let's write zinc configuration (atomic number 30) using a reduction including noble gas. Full zinc configuration looks like this: 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 3D 10. However, we see that 1S 2 2S 2 2P 6 3S 2 3P 6 is an electronic configuration of argon, noble gas. Just replace part of the recording of the electronic zinc configuration with a chemical argon symbol in square brackets (.)
   • So, the zinc electronic configuration recorded in abbreviated form has the form: 4S 2 3D 10.
   • Consider if you write the electronic configuration of noble gas, say, Argon, it is impossible to write! It is necessary to use a reduction in the noble gas facing this element; For Argon it will be neon ().

   Using the Periodic Table Adomah

   1. Lighten the Peromah periodic table. This method of recording an electronic configuration does not require memorization, however requires the presence of a converted periodic table, since in the traditional table of Mendeleev, starting at the fourth period, the period number does not correspond to the electronic shell. Find the Adomah periodic table - a special type of periodic table developed by scientist Valery Zimmerman. It is easy to find by a short search on the Internet.

      • In the periodic table Adomah, horizontal rows represent groups of elements, such as halogens, inert gases, alkali metals, alkaline earth metals, etc. The vertical columns correspond to electronic levels, and the so-called "cascades" (diagonal lines connecting blocks S, P, D and F) correspond to the periods.
      • Helium moved to hydrogen, since both of these elements are characterized by a 1s orbital. The blocks of periods (S, P, D and F) are shown on the right side, and the level numbers are given at the base. Elements are represented in rectangles numbered from 1 to 120. These numbers are conventional atomic numbers that represent the total number of electrons in the neutral atom.

   2. Find your atom in the Adomah table. To record the electronic configuration of the item, find it symbol in the Adomah periodic table and cross all the items with a large atomic number. For example, if you need to record the ERBIA electronic configuration (68), cross all the elements from 69 to 120.

      • Pay attention to the numbers from 1 to 8 at the base of the table. These are electronic levels, or speaker numbers. Ignore the speakers that contain only crossed elements. For Erbia, there are columns with numbers 1,2,3,4,5 and 6.

   3. Consider orbital sublevels to your item. Looking at the blocks of the blocks, the on the right of the table (S, P, D, and F), and on the number of the speakers shown at the base, ignore the diagonal lines between the blocks and disperse the columns on the column blocks, listing them in the bottom of the bottom up. And again ignore the blocks in which all the elements are crossed out. Write down the column blocks, ranging from the number of the column, followed by the block symbol, thus: 1S 2S 2P 3S 3P 3D 4S 4P 4D 4D 4F 5S 5P 6S (for Erbia).

      • Please note: the ER electronic configuration above is recorded in ascending order of the electronic sublayer. It can also be written in the order of filling orbital. To do this, follow the cascades from the bottom up, and not by the speakers when you record the blocks columns: 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 3D 10 4P 6 5S 2 4D 10 5P 6 6S 2 4F 12.

   4. Consider electrons for each electronic sublevel. Calculate the items in each block-column that were not deleted by attaching one electron from each item, and write their number next to the block symbol for each block-column in this way: 1S 2 2S 2 2P 6 3S 2 3P 6 3D 10 4S 2 4P 6 4D 10 4F 12 5S 2 5P 6 6S 2. In our example, this is an electronic configuration of Erbia.

   5. Consider incorrect electronic configurations. There are eighteen typical exceptions related to the electronic configurations of atoms in a state with the lowest energy, also called the main energy state. They do not obey the overall rule only by the last two-three positions occupied by electrons. In this case, the actual electronic configuration assumes the location of the electrons in a state with lower energy in comparison with the standard atom configuration. Atom-exceptions include:

      • CR(..., 3D5, 4S1); Cu.(..., 3D10, 4S1); NB.(..., 4d4, 5s1); Mo.(..., 4d5, 5s1); Ru(..., 4d7, 5s1); Rh.(..., 4d8, 5s1); Pd.(..., 4d10, 5s0); AG(..., 4d10, 5s1); LA(..., 5d1, 6s2); CE(..., 4F1, 5D1, 6S2); GD.(..., 4F7, 5D1, 6S2); AU.(..., 5d10, 6s1); AC(..., 6d1, 7s2); TH.(..., 6d2, 7s2); PA(..., 5f2, 6d1, 7s2); U.(..., 5f3, 6d1, 7s2); NP.(..., 5f4, 6d1, 7s2) and Cm.(..., 5f7, 6d1, 7s2).
   • To find the atomic number of an atom when it is recorded in the form of an electronic configuration, simply fold all the numbers that go beyond the letters (S, P, D, and F). It works only for neutral atoms, if you are dealing with an ion, then nothing will happen - you will have to add or subtract the number of additional or lost electrons.
   • The number going beyond the letter is the top index, do not make an error in the control.
   • "Stability semi-filled" sublevel does not exist. This simplification. Any stability, which relates to "half filled" sublevels, is due to the fact that each orbital is occupied by one electron, therefore the repulsion between electrons is minimized.
   • Each atom is committed to a stable state, and the most stable configurations have filled with sud and p (S2 and P6). There are such configuration for noble gases, so they rarely react and in the Mendeleev table are located on the right. Therefore, if the configuration ends with 3p 4, then it requires two electrons to achieve a stable state (in order to lose six, including the electrons of the S-sub-lineage, will need more energy, so it is easier to lose it easier). And if the configuration ends on 4D 3, then it is necessary to lose three electrons to achieve a stable state. In addition, semi-filled suits (S1, P3, D5 ..) are more stable than, for example, P4 or P2; However, S2 and P6 will be even more stable.
   • When you deal with the ion, it means that the number of protons is not equal to the number of electrons. Atom charge in this case will be depicted on top to the right (usually) from the chemical symbol. Therefore, the antimony atom with charge is +2 has an electronic configuration 1S 2 2S 2 2P 6 3S 2 3P 6 4S 2 3D 10 4P 6 5S 2 4D 10 5P 1. Please note that 5p 3 has changed to 5p 1. Be careful when the configuration of the neutral atom ends on the slips other than S and p. When you take electrons, you can pick them up only with valence orbital (S and P orbitals). Therefore, if the configuration ends with 4S 2 3D 7 and the atom receives +2 charges, the configuration will end 4S 0 3D 7. Note that 3D 7 not Changes, instead, S-orbital electrons are lost.
   • There are conditions when the electron is forced to "go to a higher energy level". When the sublayer lacks one electron to half or full of completion, take one electron from the nearest s or p- sublayer and move it to that sublayer to which an electron is necessary.
   • There are two e-configuration recording options. They can be recorded in order of increasing the number of energy levels or in order to fill electronic orbitals, as shown above for Erbia.
   • You can also record the electronic configuration of the element by writing only the valence configuration, which is the last S and P sublayer. Thus, the valence configuration of antimony will have a view of 5s 2 5p 3.
   • Ions are not the same. It is much more difficult with them. Skip the two levels and act by the same scheme depending on where you started, and on how large the number of electrons.

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.

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.

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