Malyugina O.V. Lecture 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:

    the number of energy levels of an atom = the number of the period in which the element is located;

    the maximum capacity of each energy level is calculated by the formula 2n 2

    external 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 - , 3rd -

C +6) 2 ) 4

+6 C, 2e - , 4th -

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 trueonly for elementsmajor subgroups.

Each period of the D.I. Mendeleev 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 simple substances- inert gases consist of one atom and are distinguished by chemical inertness, i.e. 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

    What energy level is called external?

    What energy level is called internal?

    What energy level is called complete?

    The elements of which group and subgroup have a completed energy level?

    What is the number of electrons in the outer energy level of the elements of the main subgroups?

    How are the elements of one main subgroup similar in the structure of the electronic level

    How many electrons at the outer level contain the elements of a) group IIA;

b) IVA group; c) Group VII A

View answer

    Last

    Any but the last

    The one that contains the maximum number of electrons. And outer level, if it contains 8 electrons for period I - 2 electrons.

    Group VIIIA elements (inert elements)

    The number of the group in which the element is located

    All elements of the main subgroups on the outer energy level contain as many electrons as the group number

    a) 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

    Define element by the following signs: a) 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.

    Which two atoms have the same number of filled energy levels?

a) sodium and hydrogen; b) helium and hydrogen; c) argon and neon d) sodium and chlorine

    How many electrons are in the outer energy level of magnesium?

    How many electrons are there in a neon atom?

    What two atoms have the same number of electrons at the external energy level: a) sodium and magnesium; b) calcium and zinc; c) arsenic and phosphorus d) oxygen and fluorine.

    At the external energy level of the sulfur atom of electrons: a) 16; b) 2; c) 6 d) 4

    What do sulfur and oxygen atoms have in common: a) the number of electrons; b) the number of energy levels c) the number of the period d) the number of electrons in the outer level.

    What do magnesium and phosphorus atoms have in common: a) the number of protons; b) the number of energy levels c) the group number d) the number of electrons in the outer level.

    Choose an element of the second period, which has one electron at the outer level: a) lithium; b) beryllium; c) oxygen; d) sodium

    There are 4 electrons at the outer level of an atom of an element of the third period. Specify this element: a) sodium; b) carbon c) silicon d) chlorine

    An atom has 2 energy levels and 3 electrons. Specify this element: a) aluminum; b) boron c) magnesium d) nitrogen

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 boron 5 B. Scheme of distribution of electrons by energy levels: 2nd - , 3rd -

b) III period, VA group, element phosphorus 15 R. Scheme of distribution of electrons by energy levels: 2nd - , 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

  1. c) arsenic and phosphorus. Atoms located in the same subgroup have the same number of electrons.

Explanations:

a) sodium and magnesium 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)

Malyugina O.V. Lecture 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:


  • the number of energy levels of an atom = the number of the period in which the element is located;

  • the maximum capacity of each energy level is calculated by the formula 2n 2

  • 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

Scheme 1

Scheme 2

1

1
1 N

1

H +1) 1


+1 H, 1e -

I (VII)

2 Not

2

He + 2 ) 2


+2 no, 2nd -

VIII

2

2
3Li

3

Li + 3 ) 2 ) 1


+ 3 Li, 2e - , 1e -
I

4 Be

4

Be +4) 2 ) 2


+ 4 Be, 2e - , 2 e -
II

5B

5

B +5) 2 ) 3


+5 B, 2e - , 3rd -
III

6C

6

C +6) 2 ) 4


+6 C, 2e - , 4th -
IV

7 N

7

N + 7 ) 2 ) 5


+ 7 N, 2e - , 5 e -
V

8 O

8

O + 8 ) 2 ) 6


+ 8 O, 2e - , 6 e -
VI

9F

9

F + 9 ) 2 ) 7


+ 9 F, 2e - , 7 e -
VI

10 Ne

10

Ne+ 10 ) 2 ) 8


+ 10 Ne, 2e - , 8 e -
VIII

3

3
11 Na

11

Na+ 11 ) 2 ) 8 ) 1


+1 1 Na, 2e - , 8e - , 1e -

I

12 mg

12

mg+ 12 ) 2 ) 8 ) 2


+1 2 mg, 2e - , 8e - , 2 e -
II

13 Al

13

Al+ 13 ) 2 ) 8 ) 3


+1 3 Al, 2e - , 8e - , 3 e -
III

14 Si

14

Si+ 14 ) 2 ) 8 ) 4


+1 4 Si, 2e - , 8e - , 4 e -
IV

15p

15

P+ 15 ) 2 ) 8 ) 5


+1 5 P, 2e - , 8e - , 5 e -
V

16S

16

S+ 16 ) 2 ) 8 ) 6


+1 5 P, 2e - , 8e - , 6 e -
VI

17Cl

17

Cl+ 17 ) 2 ) 8 ) 7


+1 7 Cl, 2e - , 8e - , 7 e -
VI

18 Ar
18

Ar+ 18 ) 2 ) 8 ) 8


+1 8 Ar, 2e - , 8e - , 8 e -
VIII

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 trueonly for elementsmajor subgroups.

Each period of the D.I. Mendeleev 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. 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 strive to complete the 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. The 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. Group VIIIA elements (inert elements)

  5. The number of the group in which the element is located

  6. All elements of the main subgroups on the outer energy level contain as many electrons as the group number

  7. a) 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 features: 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. Which two atoms have the same number of filled energy levels?
a) sodium and hydrogen; b) helium and hydrogen; c) argon and neon d) sodium and chlorine

  1. How many electrons are in the outer energy level of magnesium?

  2. How many electrons are there in a neon atom?

  3. What two atoms have the same number of electrons at the external energy level: a) sodium and magnesium; b) calcium and zinc; c) arsenic and phosphorus d) oxygen and fluorine.

  4. At the external energy level of the sulfur atom of electrons: a) 16; b) 2; c) 6 d) 4

  5. What do sulfur and oxygen atoms have in common: a) the number of electrons; b) the number of energy levels c) the number of the period d) the number of electrons in the outer level.

  6. What do magnesium and phosphorus atoms have in common: a) the number of protons; b) the number of energy levels c) the group number d) the number of electrons in the outer level.

  7. Choose an element of the second period, which has one electron at the outer level: a) lithium; b) beryllium; c) oxygen; d) sodium

  8. There are 4 electrons at the outer level of an atom of an element of the third period. Specify this element: a) sodium; b) carbon c) silicon d) chlorine

  9. An atom has 2 energy levels and 3 electrons. Specify this element: a) aluminum; b) boron c) magnesium d) nitrogen

View answer:

1. a) Set the "coordinates" chemical element: 2 electronic levels - II period; 3 electrons at the outer level - III A group. This is boron 5 B. Scheme of distribution of electrons by energy levels: 2nd - , 3rd -

B) III period, VA group, element phosphorus 15 R. Scheme of distribution of electrons by energy levels: 2nd - , 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


  1. 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)

Page 1


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, 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 donate 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.


By electronic structure external energy level 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.

2. The structure of nuclei and electron shells of atoms

2.6. Energy levels and sublevels

Most important characteristic the state of an electron in an atom is the energy of the electron, which, according to the laws quantum mechanics does not change continuously, but abruptly, i.e. can only take on well-defined values. Thus, we can speak about the presence of a set of energy levels in the atom.

Energy level- set of AO with close energy values.

Energy levels are numbered with principal quantum number n, which can only accept integers positive values(n = 1, 2, 3, ...). How more value n , the higher the energy of the electron and the given energy level. Each atom contains an infinite number of energy levels, some of which are populated by electrons in the ground state of the atom, and some are not (these energy levels are populated in the excited state of the atom).

Electronic layer- a set of electrons that are at a given energy level.

In other words, an electron layer is an energy level containing electrons.

The set of electron layers forms the electron shell of an atom.

Within the same electron layer, electrons can differ somewhat in energy, and therefore they say that energy levels are split into energy sublevels(sublayers). The number of sublevels into which a given energy level is split is equal to the number of the main quantum number of the energy level:

N (subur) \u003d n (level) . (2.4)

Sublevels are depicted using numbers and letters: the number corresponds to the number of the energy level (electronic layer), the letter corresponds to the nature of the AO that forms the sublevels (s -, p -, d -, f -), for example: 2p - sublevel (2p -AO, 2p -electron).

Thus, the first energy level (Fig. 2.5) consists of one sublevel (1s), the second - of two (2s and 2p), the third - of three (3s, 3p and 3d), the fourth of four (4s, 4p, 4d and 4f ), etc. Each sublevel contains a certain number of AO:

N (AO) = n 2 . (2.5)

Rice. 2.5. Scheme of energy levels and sublevels for the first three electron layers

1. s-type AOs are present at all energy levels, p-type appear starting from the second energy level, d-type - from the third, f-type - from the fourth, etc.

2. At a given energy level, there can be one s -, three p -, five d -, seven f -orbitals.

3. The larger the main quantum number, the more sizes AO.

Since there cannot be more than two electrons on one AO, the total (maximum) number of electrons at a given energy level is 2 times greater than the number of AOs and is equal to:

N (e) = 2n 2 . (2.6)

Thus, at a given energy level, there can be a maximum of 2 s-type electrons, 6 p-type electrons and 10 d-type electrons. In total, at the first energy level, the maximum number of electrons is 2, at the second - 8 (2 s-type and 6 p-type), at the third - 18 (2 s-type, 6 p-type and 10 d-type). These findings are conveniently summarized in Table 1. 2.2.

Table 2.2

The relationship between the principal quantum number, the number e

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, which 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 indicated 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. 1 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 electronic transitions characteristic radiation occurs. 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 Bohr's 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.