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The outer energy level (electronic shell) of their atoms contains two electrons in the s - sublevel. In this they are similar to the elements of the main subgroup. The penultimate energy level contains 18 electrons.
The external energy level of the S2 ion is filled with the maximum possible number of electrons (8), and as a result of this, the S2 ion can only exhibit electron-donating functions: by donating 2 electrons, it is oxidized to elemental sulfur, which has an oxidation number equal to zero.
If the external energy level of an atom consists of three, five, or seven electrons and the atom belongs to / J-elements, then it can give away sequentially from 1 to 7 electrons. Atoms whose outer level consists of three electrons can donate one, two, or three electrons.
If the external energy level of an atom consists of three, five, or seven electrons, and the atom belongs to the p-elements, then it can give away sequentially from one to seven electrons. Atoms whose outer level consists of three electrons can donate one, two, or three electrons.
Since the outer energy level contains two s - electrons, therefore they are similar to the elements of the PA subgroup. The penultimate energy level contains 18 electrons. If in the copper subgroup the sublevel (n - l) d10 is not yet stable, then in the zinc subgroup it is quite stable, and d - electrons in the elements of the zinc subgroup do not take part in chemical bonds.
To complete the external energy level, the chlorine atom lacks one electron.
The oxygen atom lacks two electrons to complete its outer energy level. However, in the compound of oxygen with fluorine OF2, the common electron pairs are shifted towards fluorine, as a more electronegative element.
Oxygen lacks two electrons to complete its outer energy level.
In the argon atom, the outer energy level is complete.
According to the electronic structure of the external energy level, the elements are divided into two subgroups: VA - N, P, As, Sb, Bi - non-metals and VB - V, Nb, Ta - metals. The radii of atoms and ions in the oxidation state 5 in the VA subgroup systematically increase from nitrogen to bismuth. Consequently, the difference in the structure of the pre-outer layer has little effect on the properties of the elements and they can be considered as one subgroup.
The similarity in the structure of the external energy level (Table 5) is reflected in the properties of elements and their compounds. This is explained by the fact that in the oxygen atom, unpaired electrons are located in the p-orbitals of the second layer, which can have a maximum of eight electrons.
| Parameter name | Meaning |
| Article subject: | ENERGY LEVELS |
| Rubric (thematic category) | Education |
STRUCTURE OF THE ATOM
1. Development of the theory of the structure of the atom. With
2. The nucleus and electron shell of the atom. With
3. The structure of the nucleus of an atom. With
4. Nuclides, isotopes, mass number. With
5. Energy levels.
6. Quantum-mechanical explanation of the structure.
6.1. Orbital model of the atom.
6.2. Rules for filling orbitals.
6.3. Orbitals with s-electrons (atomic s-orbitals).
6.4. Orbitals with p-electrons (atomic p-orbitals).
6.5. Orbitals with d-f electrons
7. Energy sublevels of a multielectron atom. quantum numbers.
ENERGY LEVELS
The structure of the electron shell of an atom is determined by the different energy reserves of individual electrons in the atom. In accordance with the Bohr model of the atom, electrons can occupy positions in the atom that correspond to precisely defined (quantized) energy states. These states are called energy levels.
The number of electrons that can be on a separate energy level is determined by the formula 2n 2, where n is the number of the level, which is denoted by Arabic numerals 1 - 7. The maximum filling of the first four energy levels in. in accordance with the formula 2n 2 is: for the first level - 2 electrons, for the second - 8, for the third -18 and for the fourth level - 32 electrons. The maximum filling of higher energy levels in atoms of known elements with electrons has not been achieved.
Rice. 1 shows the filling of the energy levels of the first twenty elements with electrons (from hydrogen H to calcium Ca, black circles). By filling in the energy levels in the indicated order, the simplest models of the atoms of the elements are obtained, while observing the order of filling (from bottom to top and from left to right in the figure) in such a way that the last electron points to the symbol of the corresponding element At the third energy level M(maximum capacity is 18 e -) for elements Na - Ar contains only 8 electrons, then the fourth energy level begins to build up N- two electrons appear on it for the elements K and Ca. The next 10 electrons again occupy the level M(elements Sc – Zn (not shown), and then the filling of the N level with six more electrons continues (elements Ca-Kr, white circles).
| Rice. one |  Rice. 2 |
If the atom is in the ground state, then its electrons occupy levels with a minimum energy, i.e., each subsequent electron occupies the energetically most favorable position, such as in Fig. 1. With an external impact on an atom associated with the transfer of energy to it, for example, by heating, electrons are transferred to higher energy levels (Fig. 2). This state of the atom is called excited. The place vacated at the lower energy level is filled (as an advantageous position) by an electron from a higher energy level. During the transition, the electron gives off a certain amount of energy, ĸᴏᴛᴏᴩᴏᴇ corresponds to the energy difference between the levels. As a result of electronic transitions, characteristic radiation arises. From the spectral lines of the absorbed (emitted) light, one can make a quantitative conclusion about the energy levels of the atom.
In accordance with the Bohr quantum model of the atom, an electron having a certain energy state moves in a circular orbit in the atom. Electrons with the same energy reserve are at equal distances from the nucleus, each energy level corresponds to its own set of electrons, called the electron layer by Bohr. Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, according to Bohr, the electrons of one layer move along a spherical surface, the electrons of the next layer along another spherical surface. all spheres are inscribed one into another with the center corresponding to the atomic nucleus.
ENERGY LEVELS - concept and types. Classification and features of the category "ENERGY LEVELS" 2017, 2018.
The closer to the atomic nucleus is the electron shell of the atom, the stronger the electrons are attracted to the nucleus and the greater their binding energy with the nucleus. Therefore, the arrangement of electron shells is conveniently characterized by energy levels and sublevels and the distribution of electrons over them. The number of electronic energy levels is equal to the number of the period, in which the element is located. The sum of the numbers of electrons at the energy levels is equal to the ordinal number of the element.
The electronic structure of the atom is shown in fig. 1.9 in the form of a diagram of the distribution of electrons over energy levels and sublevels. The diagram consists of electronic cells depicted by squares. Each cell symbolizes one electron orbital capable of accepting two electrons with opposite spins, indicated by the up and down arrows.
Rice. 1.9.
The electronic diagram of an atom is built in the sequence increasing the energy level number. In the same direction the energy of the electron increases and the energy of its connection with the nucleus decreases. For clarity, we can imagine that the nucleus of the atom is "at the bottom" of the diagram. The number of electrons in an atom of an element is equal to the number of protons in the nucleus, i.e. element's atomic number in the periodic table.
The first energy level consists of only one orbital, which is denoted by the symbol s. This orbital is filled with hydrogen and helium electrons. Hydrogen has one electron, and hydrogen is monovalent. Helium has two paired electrons with opposite spins, helium has zero valency and does not form compounds with other elements. The energy of a chemical reaction is not enough to excite a helium atom and transfer an electron to the second level.
The second energy level consists of. "-sublevel and /. (-sublevel, which has three orbitals (cells). Lithium sends the third electron to the 2"-sublevel. One unpaired electron causes lithium to be monovalent. Beryllium fills the same sublevel with the second electron, therefore, in In the unexcited state, beryllium has two paired electrons.However, an insignificant excitation energy turns out to be sufficient to transfer one electron to the ^-sublevel, which makes beryllium bivalent.
The further filling of the 2p-sublevel proceeds in a similar way. Oxygen in compounds is divalent. Oxygen does not exhibit higher valences due to the impossibility of pairing second-level electrons and transferring them to the third energy level.
In contrast to oxygen, sulfur located under oxygen in the same subgroup can exhibit valences 2, 4 and 6 in its compounds due to the possibility of depairing the electrons of the third level and moving them to the ^-sublevel. Note that other valence states of sulfur are also possible.
Elements whose s-sublevel is filled are called “-elements. Similarly, the sequence is formed R- elements. Elements s- and p-sublevels are included in the main subgroups. Elements of secondary subgroups are ^-elements (wrong name - transitional elements).
It is convenient to denote subgroups by the symbols of electrons, due to which the elements included in the subgroup were formed, for example s"-subgroup (hydrogen, lithium, sodium, etc.) or //-subgroup (oxygen, sulfur, etc.).
If the periodic table is constructed in such a way that the period numbers increase from bottom to top, and first one and then two electrons are placed in each electron cell, a long-period periodic table will be obtained, resembling a diagram of the distribution of electrons over energy levels and sublevels.
Malyugin 14. External and internal energy levels. Completion of the energy level.
Let us briefly recall what we already know about the structure of the electron shell of atoms:
ü the number of energy levels of the atom = the number of the period in which the element is located;
ü the maximum capacity of each energy level is calculated by the formula 2n2
ü the outer energy shell cannot contain more than 2 electrons for elements of period 1, more than 8 electrons for elements of other periods
Once again, let us return to the analysis of the scheme for filling energy levels in elements of small periods:
Table 1. Filling of energy levels
for elements of small periods
Period number | Number of energy levels = period number | Element symbol, its ordinal number | Total electrons | Distribution of electrons by energy levels | Group number |
|
|
H +1 )1 | +1 H, 1e- | |||||
|
He + 2 ) 2 | +2 No, 2nd | |||||
|
Li + 3 ) 2 ) 1 | + 3 Li, 2e-, 1e- | |||||
|
Be +4 ) 2 )2 | + 4 Be, 2e-,2 e- | |||||
|
B +5 ) 2 )3 | +5 B, 2e-, 3e- | |||||
|
C +6 ) 2 )4 | +6 C, 2e-, 4e- | |||||
|
N + 7 ) 2 ) 5 | + 7 N, 2e-,5 e- | |||||
|
O + 8 ) 2 ) 6 | + 8 O, 2e-,6 e- | |||||
|
F + 9 ) 2 ) 7 | + 9 F, 2e-,7 e- | |||||
|
Ne + 10 ) 2 ) 8 | + 10 Ne, 2e-,8 e- | |||||
|
Na + 11 ) 2 ) 8 )1 | +1 1 Na, 2e-, 8e-, 1e- | |||||
|
mg + 12 ) 2 ) 8 )2 | +1 2 mg, 2e-, 8e-, 2 e- | |||||
|
Al + 13 ) 2 ) 8 )3 | +1 3 Al, 2e-, 8e-, 3 e- | |||||
|
Si + 14 ) 2 ) 8 )4 | +1 4 Si, 2e-, 8e-, 4 e- | |||||
|
P + 15 ) 2 ) 8 )5 | +1 5 P, 2e-, 8e-, 5 e- | |||||
|
S + 16 ) 2 ) 8 )6 | +1 5 P, 2e-, 8e-, 6 e- | |||||
|
Cl + 17 ) 2 ) 8 )7 | +1 7 Cl, 2e-, 8e-, 7 e- | |||||
18 Ar |
Ar+ 18 ) 2 ) 8 )8 | +1 8 Ar, 2e-, 8e-, 8 e- |
Analyze table 1. Compare the number of electrons in the last energy level and the number of the group in which the chemical element is located.
Have you noticed that the number of electrons in the outer energy level of atoms is the same as the group number, in which the element is located (the exception is helium)?
!!! This rule is true only for elements major subgroups.
Each period of the system ends with an inert element(helium He, neon Ne, argon Ar). The external energy level of these elements contains the maximum possible number of electrons: helium -2, the remaining elements - 8. These are elements of group VIII of the main subgroup. The energy level similar to the structure of the energy level of an inert gas is called completed. This is a kind of strength limit of the energy level for each element of the Periodic system. Molecules of simple substances - inert gases, consist of one atom and are distinguished by chemical inertness, i.e., they practically do not enter into chemical reactions.
For the remaining elements of the PSCE, the energy level differs from the energy level of the inert element, such levels are called unfinished. The atoms of these elements tend to complete their outer energy level by donating or accepting electrons.
Questions for self-control
1. What energy level is called external?
2. What energy level is called internal?
3. What energy level is called complete?
4. Elements of which group and subgroup have a completed energy level?
5. What is the number of electrons in the outer energy level of the elements of the main subgroups?
6. How are the elements of one main subgroup similar in the structure of the electronic level
7. How many electrons at the outer level contain the elements of a) group IIA;
b) IVA group; c) Group VII A
View answer
1. Last
2. Any but the last
3. The one that contains the maximum number of electrons. As well as the outer level, if it contains 8 electrons for period I - 2 electrons.
4. Elements of group VIIIA (inert elements)
5. The number of the group in which the element is located
6. All elements of the main subgroups on the external energy level contain as many electrons as the group number
7. a) the elements of group IIA have 2 electrons in the outer level; b) group IVA elements have 4 electrons; c) elements of group VII A have 7 electrons.
Tasks for independent solution
1. Determine the element according to the following criteria: a) it has 2 electronic levels, on the outer - 3 electrons; b) has 3 electronic levels, on the outer - 5 electrons. Write down the distribution of electrons over the energy levels of these atoms.
2. What two atoms have the same number of filled energy levels?
View answer:
1. a) Let's establish the "coordinates" of the chemical element: 2 electronic levels - II period; 3 electrons at the outer level - III A group. This is a 5B bur. Scheme of distribution of electrons by energy levels: 2e-, 3e-
b) III period, VA group, element phosphorus 15Р. Scheme of distribution of electrons by energy levels: 2e-, 8e-, 5e-
2. d) sodium and chlorine.
Explanation: a) sodium: +11 )2)8 )1 (filled 2) ←→ hydrogen: +1)1
b) helium: +2 )2 (filled 1) ←→ hydrogen: hydrogen: +1)1
c) helium: +2 )2 (filled 1) ←→ neon: +10 )2)8 (filled 2)
*G) sodium: +11 )2)8 )1 (filled 2) ←→ chlorine: +17 )2)8 )7 (filled 2)
4. Ten. Number of electrons = serial number
5 c) arsenic and phosphorus. Atoms located in the same subgroup have the same number of electrons.
Explanations:
a) sodium and magnesium (in different groups); b) calcium and zinc (in the same group, but different subgroups); * c) arsenic and phosphorus (in one, main, subgroup) d) oxygen and fluorine (in different groups).
7. d) the number of electrons in the outer level
8. b) the number of energy levels
9. a) lithium (located in group IA of period II)
10. c) silicon (IVA group, III period)
11. b) boron (2 levels - IIperiod, 3 electrons in the outer level - IIIAGroup)
What happens to the atoms of elements during chemical reactions? What are the properties of the elements? One answer can be given to both of these questions: the reason lies in the structure of the external In our article, we will consider the electronic of metals and non-metals and find out the relationship between the structure of the external level and the properties of the elements.
Special properties of electrons
When a chemical reaction occurs between the molecules of two or more reagents, changes occur in the structure of the electron shells of atoms, while their nuclei remain unchanged. First, let's get acquainted with the characteristics of electrons located at the most distant levels of the atom from the nucleus. Negatively charged particles are arranged in layers at a certain distance from the nucleus and from each other. The space around the nucleus where electrons are most likely to be found is called the electron orbital. About 90% of the negatively charged electron cloud is condensed in it. The electron itself in the atom exhibits the property of duality, it can simultaneously behave both as a particle and as a wave.
Rules for filling the electron shell of an atom
The number of energy levels on which the particles are located is equal to the number of the period where the element is located. What does the electronic composition indicate? It turned out that the number of electrons in the outer energy level for s- and p-elements of the main subgroups of small and large periods corresponds to the group number. For example, lithium atoms of the first group, which have two layers, have one electron in the outer shell. Sulfur atoms contain six electrons at the last energy level, since the element is located in the main subgroup of the sixth group, etc. If we are talking about d-elements, then the following rule exists for them: the number of external negative particles is 1 (for chromium and copper) or 2. This is explained by the fact that as the charge of the nucleus of atoms increases, the internal d-sublevel is first filled and the external energy levels remain unchanged.
Why do the properties of elements of small periods change?
Periods 1, 2, 3 and 7 are considered small. A smooth change in the properties of elements as nuclear charges increase, starting from active metals and ending with inert gases, is explained by a gradual increase in the number of electrons at the external level. The first elements in such periods are those whose atoms have only one or two electrons that can easily break away from the nucleus. In this case, a positively charged metal ion is formed.
Amphoteric elements, such as aluminum or zinc, fill their external energy levels with a small amount of electrons (1 for zinc, 3 for aluminum). Depending on the conditions of the chemical reaction, they can exhibit both the properties of metals and non-metals. Non-metallic elements of small periods contain from 4 to 7 negative particles on the outer shells of their atoms and complete it to an octet, attracting electrons from other atoms. For example, a non-metal with the highest electronegativity index - fluorine, has 7 electrons on the last layer and always takes one electron not only from metals, but also from active non-metallic elements: oxygen, chlorine, nitrogen. Small periods end, as well as large ones, with inert gases, whose monatomic molecules have completely completed external energy levels up to 8 electrons.
Features of the structure of atoms of large periods
The even rows of 4, 5, and 6 periods consist of elements whose outer shells contain only one or two electrons. As we said earlier, they fill the d- or f- sublevels of the penultimate layer with electrons. Usually these are typical metals. Their physical and chemical properties change very slowly. Odd rows contain such elements, in which the external energy levels are filled with electrons according to the following scheme: metals - amphoteric element - non-metals - inert gas. We have already observed its manifestation in all small periods. For example, in an odd series of 4 periods, copper is a metal, zinc is an amphoterene, then from gallium to bromine, non-metallic properties are enhanced. The period ends with krypton, the atoms of which have a completely completed electron shell.
How to explain the division of elements into groups?
Each group - and there are eight of them in the short form of the table, is also divided into subgroups, called main and secondary. This classification reflects the different positions of electrons on the external energy level of the atoms of elements. It turned out that the elements of the main subgroups, for example, lithium, sodium, potassium, rubidium and cesium, the last electron is located on the s-sublevel. Elements of the 7th group of the main subgroup (halogens) fill their p-sublevel with negative particles.
For representatives of side subgroups, such as chromium, the filling of the d-sublevel with electrons will be typical. And for the elements included in the family, the accumulation of negative charges occurs at the f-sublevel of the penultimate energy level. Moreover, the group number, as a rule, coincides with the number of electrons capable of forming chemical bonds.
In our article, we found out what structure the external energy levels of atoms of chemical elements have, and determined their role in interatomic interactions.
