Home → About separation Characteristics of an element by its position in psche presentation for a chemistry lesson (grade 9) on the topic. General characteristics of chemical elements Characteristics of a chemical element based on its

Characteristics of an element by its position in psche presentation for a chemistry lesson (grade 9) on the topic. General characteristics of chemical elements Characteristics of a chemical element based on its

In this lesson you will learn about Mendeleev's Periodic Law, which describes the change in the properties of simple bodies, as well as the shapes and properties of compounds of elements depending on the size of their atomic masses. Consider how a chemical element can be described by its position in the Periodic Table.

Topic: Periodic law andPeriodic table of chemical elements by D. I. Mendeleev

Lesson: Description of an element by position in D. I. Mendeleev’s Periodic Table of Elements

In 1869, D.I. Mendeleev, based on data accumulated on chemical elements, formulated his periodic law. Then it sounded like this: “The properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the magnitude of the atomic masses of the elements.” For a very long time, the physical meaning of D.I. Mendeleev’s law was unclear. Everything fell into place after the discovery of the structure of the atom in the 20th century.

Modern formulation of the periodic law:“The properties of simple substances, as well as the forms and properties of compounds of elements, are periodically dependent on the magnitude of the charge of the atomic nucleus.”

The charge of the nucleus of an atom is equal to the number of protons in the nucleus. The number of protons is balanced by the number of electrons in an atom. Thus, the atom is electrically neutral.

Charge of the nucleus of an atom in the periodic table it is element serial number.

Period number shows number of energy levels, on which electrons rotate.

Group number shows number of valence electrons. For elements of the main subgroups, the number of valence electrons is equal to the number of electrons in the outer energy level. It is the valence electrons that are responsible for the formation of chemical bonds of an element.

Chemical elements of group 8 - inert gases - have 8 electrons in their outer electron shell. Such an electron shell is energetically favorable. All atoms strive to fill their outer electron shell with up to 8 electrons.

What characteristics of an atom change periodically in the Periodic Table?

The structure of the external electronic level is repeated.

The radius of an atom changes periodically. In a group radius increases with increasing period number, as the number of energy levels increases. In period from left to right the atomic nucleus will grow, but the attraction to the nucleus will be greater and therefore the radius of the atom decreases.

Each atom strives to complete the last energy level. Elements of group 1 have 1 electron in the last layer. Therefore, it is easier for them to give it away. And it is easier for elements of group 7 to attract 1 electron missing to the octet. In a group, the ability to give up electrons will increase from top to bottom, as the radius of the atom increases and the attraction to the nucleus decreases. In a period from left to right, the ability to give up electrons decreases because the radius of the atom decreases.

The more easily an element gives up electrons from its outer level, the greater its metallic properties, and its oxides and hydroxides have greater basic properties. This means that metallic properties in groups increase from top to bottom, and in periods from right to left. With non-metallic properties the opposite is true.

Rice. 1. Position of magnesium in the table

In the group, magnesium is adjacent to beryllium and calcium. Fig.1. Magnesium ranks lower than beryllium but higher than calcium in the group. Magnesium has more metallic properties than beryllium, but less than calcium. The basic properties of its oxides and hydroxides also change. In the period, sodium is to the left, and aluminum is to the right of magnesium. Sodium will exhibit more metallic properties than magnesium, and magnesium will exhibit more metallic properties than aluminum. Thus, you can compare any element with its neighbors in the group and period.

Acidic and non-metallic properties change in opposition to the basic and metallic properties.

Characteristics of chlorine by its position in the periodic table of D.I. Mendeleev.

Rice. 4. Chlorine position in the table

. The atomic number 17 shows the number of protons17 and electrons17 in an atom. Fig.4. Atomic mass 35 will help calculate the number of neutrons (35-17 = 18). Chlorine is in the third period, which means the number of energy levels in an atom is 3. It is in the 7-A group and belongs to the p-elements. This is a non-metal. We compare chlorine with its neighbors in the group and in the period. The non-metallic properties of chlorine are greater than those of sulfur, but less than those of argon. Chlorine has less metallic properties than fluorine and more than bromine. Let's distribute electrons among energy levels and write the electron formula. The overall distribution of electrons will look like this. See Fig. 5

Rice. 5. Distribution of electrons of the chlorine atom over energy levels

Determine the highest and lowest oxidation states of chlorine. The highest oxidation state is +7, since it can give up 7 electrons from the last electron layer. The lowest oxidation state is -1 because chlorine needs 1 electron to complete. Formula of higher oxide Cl 2 O 7 (acid oxide), hydrogen compound HCl.

In the process of donating or gaining electrons, an atom acquires conventional charge. This conditional charge is called .

- Simple substances have an oxidation state equal to zero.

Items may exhibit maximum oxidation state and minimum. Maximum An element exhibits its oxidation state when gives away all of its valence electrons from the outer electron level. If the number of valence electrons is equal to the group number, then the maximum oxidation state is equal to the group number.

Rice. 2. Position of arsenic in the table

Minimum An element will exhibit an oxidation state when it will accept all possible electrons to complete the electron layer.

Let's consider the values of oxidation states using element No. 33 as an example.

This is arsenic As. It is in the fifth main subgroup. Fig. 2. It has five electrons in its final electron level. This means that when giving them away, he will have an oxidation state of +5. The As atom lacks 3 electrons before completing the electron layer. By attracting them, it will have an oxidation state of -3.

Position of elements of metals and non-metals in the Periodic Table D.I. Mendeleev.

Rice. 3. Position of metals and non-metals in the table

IN side subgroups are all metals . If you mentally conduct diagonal from boron to astatine , That higher of this diagonal in the main subgroups there will be all nonmetals , A below this diagonal is everything metals . Fig.3.

1. Nos. 1-4 (p. 125) Rudzitis G.E. Inorganic and organic chemistry. 8th grade: textbook for general education institutions: basic level / G. E. Rudzitis, F.G. Feldman. M.: Enlightenment. 2011, 176 pp.: ill.

2. What characteristics of an atom change with periodicity?

3. Characterize the chemical element oxygen according to its position in the Periodic Table of D.I. Mendeleev.

1. Give characteristics of the elements: a) phosphorus; b) potassium.

2. Write down the equations of chemical reactions and characterizing properties: Write down the equations of reactions involving electrolytes also in ionic form.

3. Give the characteristics of magnesium - a simple substance. What type of connection is observed in it? What physical properties does the metal magnesium have? Write down the equations for the reaction of magnesium with the following substances: a) oxygen; b) chlorine Cl2; c) sulfur; d) nitrogen N2; e) hydrochloric acid. Consider them from the standpoint of oxidation-reduction processes.

Magnesium is a simple substance, characterized by a metallic crystal lattice; it has a metallic luster and electrical conductivity.

4. What is allotropy? What type of chemical bond is realized in the molecules of the composition: a) S8; b) H2S? What physical properties does the most stable modification of sulfur, rhombic sulfur, have? Write down the equations for the reactions of sulfur with the following substances: a) sodium; b) calcium; c) aluminum; d) oxygen; e) hydrogen; e) fluorine F2. Consider them from the standpoint of oxidation-reduction processes.

Allotropy is the phenomenon of the existence of a chemical element in the form of several simple substances, different in structure and properties (so-called allotropic forms).

5. Compare the properties of the simple substance silicon with the properties of simple substances formed by chemical elements - silicon’s neighbors in period.

The non-metallic properties of silicon are less pronounced than those of phosphorus, but stronger than those of aluminum.

6. The highest oxide of which chemical element has the most pronounced acidic properties: a) nitrogen or phosphorus, b) phosphorus or sulfur?

a) Nitrogen has more acidic properties than phosphorus, since in groups from top to bottom the basic properties are strengthened and the acidic properties are weakened.

b) Sulfur’s acidic properties are more pronounced than those of phosphorus, because in periods from left to right, acidic properties are strengthened and basic properties are weakened.

7. Calculate the volume of air (assume the volume fraction of oxygen in it to be 0.2) that will be required to burn a 120 mg sample of magnesium containing 2% non-combustible impurities.

8. Calculate the volume of sulfur (IV) oxide (no.) that can be obtained by burning 1.6 kg of sulfur if the product yield is 80% of the theoretically possible.

9. Is it possible to say that the highest sulfur oxide SO3 corresponds to sulfurous acid H2SO3? Why?

Subject: Characteristics of a chemical element by its position in the periodic table of chemical elements.

Lesson objectives:

To teach how to draw up a plan for the general characteristics of an element according to its position in the periodic table of chemical elements; consolidate the ability to characterize an element, its properties and the properties of its compounds by position in the periodic table;

Develop the ability to independently obtain and use the necessary information, the ability to draw conclusions based on the information received;

Developing the ability to work independently and in a group.

Lesson type: combined.

Lesson format: individual, group.

Lesson methods: method of developing critical thinking “tree of knowledge”, independent completion of tasks in groups, defense of posters, learning through dialogue between teacher and students.

Equipment: PSHE, handouts (apples, emoticons, assessment sheets, self-assessment test for reflection, Whatman paper and markers), interactive whiteboard, presentation.

Lesson progress

1. Organizational moment (3 min). Greetings.

We divide the class into 4 groups using chemical elements. Students who draw cards with the same element form one group. Elements: sodium, aluminum, phosphorus, chlorine.Selecting speakers who distribute work within the group and keep a score sheet.

Score sheets are distributed to the groups. Explanations on the score sheet.

2. Checking homework (11 min). Teacher: Guys, what topic did you study in the last lesson? (PZ and PSHE) Today, to test your knowledge on this topic, I offer you the following task. We use the “Tree of Knowledge” technique. Students work individually. On the interactive board there is a drawing of a tree with apples of three colors: red, yellow, green. There's a question behind every apple. Students are invited to analyze their work while studying the previous topic and, having weighed their options, “harvest”, taking into account that

“red apples are already ripe” - they hang high, it’s hard to pick them - the questions on them are the most difficult,

“yellow apples” - hang lower, easier to pick - questions are also easier,

“green apples” hang very low, so the questions are the simplest.

Students take turns choosing apples and corresponding questions. The children answer the questions orally, and the teacher receives good material for diagnosing not only the mastery of the topic, but also the level of self-esteem of the students. Paper apples of different colors are given to children for correct answers.

Questions for green cards.

Who and when was the periodic law discovered? (D.I.Mendeleev. 1869)

The formulation of the periodic law given by D.I. Mendeleev. (The properties of elements, as well as the composition and properties of the simple and complex substances they form, are periodically dependent on their atomic masses)

Modern formulation of the periodic law. (The properties of chemical elements and the simple and complex substances they form are periodically dependent on the magnitude of the nuclear charge of the atom of these elements)

What is a period? (A period is a series of chemical elements arranged in order of increasing atomic masses. The period begins with an alkali metal and ends with an inert element)

What is the periodic table of chemical elements? (The periodic table of chemical elements is a graphic representation of the periodic law and the natural classification of chemical elements)

How are periods divided? Why? (Small periods: 1-3 periods contain 2-8 chemical elements, large periods: 4-7 periods contain 18-32 chemical elements)

What is the group? How many groups? (A group is a vertical row in which elements belonging to the same family with the same number of external electrons and, accordingly, exhibiting the same properties are located. 8 groups.)

What elements form the main subgroups? (Elements of small and large periods)

What elements form side subgroups? (Transition elements of large periods)

Which groups of elements form volatile compounds with hydrogen? (Elements of the main subgroups of groups IV-VII)

Questions for yellow cards.

What properties of chemical elements did D.I. Mendeleev use as the basis for their classification? (Atomic mass, valency of chemical elements and properties of the compounds they form)

Which of the proposed elements exhibits the most pronounced non-metallic properties: oxygen, sulfur, selenium, tellurium? Explain why? (Oxygen. In the main subgroups, from top to bottom, non-metallic properties weaken, and metallic properties increase)

How do the properties of chemical elements change over periods? (From left to right, metallic properties weaken, non-metallic properties increase)

Which of the proposed elements exhibits the most pronounced metallic properties: magnesium, calcium, strontium, barium? Explain why? (Barium. In the main subgroups from top to bottom, metallic properties increase, non-metallic properties weaken)

Which of the proposed elements has the most pronounced non-metallic elements: magnesium, silicon, sulfur, chlorine? Explain why? (Chlorine. In periods from left to right, non-metallic properties increase)

Which of the proposed elements has the most pronounced metallic properties: sodium, magnesium, aluminum, silicon? Explain why? (Sodium. In periods from left to right, metallic properties weaken)

Questions for red cards.

What is the main reason for changes in the properties of elements in a period? (In a gradual increase in the number of protons in the nucleus and the number of electrons in the outer energy level)

What is the reason for the increase in the metallic properties of elements in the main subgroups from top to bottom? (As the charge of nuclei increases, the number of energy levels increases, the outer valence electrons move away from the nucleus, the bond with the nucleus weakens and, accordingly, the metallic properties increase)

Why has the modern formulation of the periodic law changed? (In connection with the discovery of the structure of the atom. The main characteristic of a chemical element is not its atomic mass, but the charge of the nucleus of its atom. It is the charge of the nucleus of an atom that determines the number of electrons, and the number of electrons in an atom and their distribution among levels determines the properties of chemical elements and their compounds)

For each correct answer, students receive apples of the corresponding color. Green apples - 1 point, yellow - 2 points, red - 3 points.

The number of students' points on the assessment sheets is noted by speakers from each group.

Score sheet

Group _____________ Speaker _______________________

Number of apples

Quantity

in smai

faces

Points by number of apples:

Green - 1 point

Yellow-2 points

Red-3 points

Points based on the number of emoticons:

1 point for each emoticon

Sune th points

Lesson grade

Green-

Yellow-Red-

Green-

Yellow-Red-

Green-

Yellow-Red-

Green-

Yellow-Red-

Green-

Yellow-Red-

Green-

Yellow-Red-

Converting points to grades:

1-4 points – score “3”

5-8 points – score “4”

9 points or more – score “5”

The speaker needs to familiarize students with their grades within the group.

3. Studying a new topic (6 min).

Teacher: Guys, you have studied such topics as “Composition and structure of the atom”, “Periodic law and the periodic system of chemical elements”. Today in the lesson we will learn how to characterize a chemical element by its position in the periodic table of chemical elements. Write down the topic of the lesson in your notebooks: “Characteristics of a chemical element by its position in the periodic table of chemical elements.” The main characteristic of an atom is its structure, i.e. such characteristics as nuclear charge, electron level distribution, valence. Tell me, can we get this information from the periodic table of chemical elements?

Let's remember and fill out the table showing the relationship between the main characteristics of the Periodic Table and the structure of the element's atom.

Students draw a table and fill it out in their notebooks.

The main characteristics of elements and their relationship with the structure of atoms.

Questions asked while filling out the table:

1. What is the main characteristic of a chemical element in the periodic table of chemical elements? (serial number)

2. What can be determined in the structure of an atom by the serial number of a chemical element? (positive nuclear charge, number of protons and total number of electrons)

3. What other characteristics of the Periodic Table do we know? (period number, group number)

4. What can be determined by the number of the period in which a chemical element is located? (number of electron layers in an atom of this element)

5. What can be determined by the group number in which a chemical element is located? (Number of electrons in the outer electron layer (for elements of the main subgroups), highest valency in oxygen compounds)

Students receive emoticons for correct answers.

A plan for characterizing chemical elements based on the theory of the structure of the atom and its position in the periodic table.

2. Position of the element in the periodic table of chemical elements:

Serial number

Relative atomic mass, A r

Period

Group, subgroup.

№12th element

A r ( Mg)=24

3rd period

Group II, main subgroup

3. Composition and structure of the element’s atom:

Atomic composition

Distribution of electrons by levels

Electronic formula of an atom

Graphical electronic formula

24 _

12 Mg(12r, 12n), 12e

12 Mg)2)8)2

1s 2 2s 2 2p 6 3s 2 3p 0 3d 0

1 s 2 2s 2 2p 6 3s 2 3p 0

4. Properties of a simple substance formed by this element:

Metal or non-metal, or exhibits amphoteric properties

Higher valence

Mg- metal

Valence is constant -ІІ

5. Formula of superior oxide and volatile hydrogen compound

MgO - magnesium oxide,

During the review of the plan for the characteristics of a chemical element, students are asked clarifying and supplementary questions, for the answers to which students are given emoticons:

1. How is the number of neutrons in an atom determined? (we find by the difference between the relative atomic mass and the atomic number:N= A r - Z)

2. How do we determine the maximum number of electrons that can be accommodated in a level? (according to the formulaN=2 n 2 )

3. How many electrons can be maximally placed in the first, second, third, fourth levels? (the first has 2 electrons, the second has 8 electrons, the third has 18 electrons, the fourth has 32 electrons)

4. What sublevels are there at each level? (at the first level -s-sublevel, on the second-sAndp-sublevels, on the third –s, pAndd-sublevels, on the fourth-s, p, dAndf-sublevels)

5. How many electrons can be accommodated in each sublevel? (ons-sublevel 2 electrons, onp-sublevel 6 electrons, ond-sublevel of 10 electrons andf-sublevel 14 electrons)

6. How can the properties of elements be determined by the number of outer electrons? (1-3 electrons - metal, 4-8 electrons - non-metal)

7. What is the highest valence of a chemical element in oxides? (the highest valency can be determined by the group number for elements of the main subgroups)

4. Consolidation (18 min). Teacher:Next, each group completes the following tasks (on the interactive whiteboard). The assessment of this task is carried out by the speaker. The speaker will decide who to give the emoticon based on the following criteria: the student’s participation in completing a task on whatman paper and speaking in front of the class.

1 task. Students in each group use whatman paper to characterize the element by which they were divided into groups at the beginning of the lesson: sodium, aluminum, phosphorus, chlorine.

Student answers:

Na, sodium

Al,aluminum

P,phosphorus

Cl,chlorine

№11 element

A r ( Na)=23

3rd period

Group I, main subgroup

№13th element

A r ( Al)=27

3rd period

І І Group I, main subgroup

№15 element

A r ( P)=31

3rd period

Vgroup, main subgroup

№17th element

A r ( Cl)=35,5

3rd period

VGroup II, main subgroup

23 _

11 Na (11r, 12n), 11e

11 Na)2)8)1

1s 2 2s 2 2p 6 3s 1 3p 0 3d 0

1 s 2 2s 2 2p 6 3s 2 3p 0

27 _

13 Al (13r, 14n), 13e

13 Al)2)8)3

1s 2 2s 2 2p 6 3s 2 3p 1 3d 0

1 s 2 2s 2 2p 6 3s 2 3p 1

31 _

15 P(15r, 16n), 15e

15 P)2)8)5

1s 2 2s 2 2p 6 3s 2 3p 3 3d 0

1 s 2 2s 2 2p 6 3s 2 3p 3

35 _

17 Cl (17r, 18n), 17e

17 Cl)2)8)7

1s 2 2s 2 2p 6 3s 2 3p 5 3d 0

1 s 2 2s 2 2p 6 3s 2 3p 0

Na- metal

Valence is constant -І

Al- amphoteric element

Constant valence - III

P-non-metal

Cl-non-metal

Valence is variable, highest valence isVII

Na 2 O - sodium oxide,

does not form a volatile hydrogen compound

Al 2 O 3 - aluminum oxide,

does not form a volatile hydrogen compound

P 2 O 5 - phosphorus oxide (V),

PH 3

Cl 2 O 7 - chlorine oxide (VII)

volatile hydrogen compound -HCl

Students defend their posters. We evaluate the work of students in groups together with the speakers. Teacher: Speaker, which of the students in your group would you like to give emoticons for completing this task? Emoticons are distributed to group members.

Group speakers count the number of points based on the number of apples and emoticons.

If you have time left, you can complete the next task.

Task 2. (if there is time left to complete it)

Group task Na .

Name the element based on the following data: it is in group III, the relative molecular weight of the higher oxide is 102.

a) Aluminum; b) Scandium; c) Gallium.

Given: Solution:

R2O3

Mr(R2O3)=102

Mr(R2O3)=102, Ar(O)=16

2x+16*3=102

2x=102-48

2x=54

x=27

R-?

This Ar corresponds to the element Al.

Answer: Aluminum.

Group task Al .

Name the element based on the following data: it is in group VI, the relative molecular weight of the higher oxide is 80.

a) Sulfur; b) Selenium; c) Tellurium

Given: Solution:

RO3

Mr(RO3)

Mr(RABOUT3)=80, Ar(O)=16

R-?

x+16*3=80,

x=80-48=32

This Ar corresponds to the element S.

Answer: Sulfur

Group task P .

Name the element based on the following data: it is in group IV, the relative molecular weight of the higher oxide is 60.

a) Tin; b) Silicon; c) Carbon

RO2

Mr(RO2)=60

Mr(RO2)=60, Ar(O)=16

x+32=60

x=60-32=28

R-?

Given: Solution:

This Ar corresponds to the element Si.

Answer: Silicon

Group task Cl .

Name the element based on the following data: it is in group V, the relative molecular weight of the higher oxide is 108.

a) Nitrogen; b) Phosphorus; c) Arsenic.

Given: Solution:

R2O5

Mr(R2O5)=108

Mr(R2O5)=102, Ar(O)=16

2x+16*5=108

2x=108-80

2x=28

x=214

R-?

This Ar corresponds to the element N.

Answer: Nitrogen

Homework (1 min) §59, characterize two elements: metal and non-metal according to plan.

Assessment (2 min) Speakers put down points and grades on the score sheets and introduce group members to their grades for the lesson.

Reflection (3 min)

Based on the results of your work in the lesson, you need to establish the degree to which the educational goal has been achieved and the acquisition of confidence in your knowledge.

I suggest you analyze what you learned in class. Run the test.

F.I. student__________________________________________

Test (for self-analysis of acquired knowledge and acquired skills)

a) plan for the characteristics of an element by position in the periodic table

b) logical sequence of characteristics of an element by position in the periodic table

2) I can define for an element:

a) the number of elementary particles (protons, neutrons, electrons) in an atom

b) number of energy levels

c) electronic formula

d) the number of electrons in the outer level of an atom

e) valency of the element

f) the highest oxidation state of the element

g) the element being described is a metal or non-metal

h) formula of higher oxide and hydrogen compound

3) I can compare the properties of an element with the properties of neighboring elements in the periodic table

Summing up.

Purpose of the work: learn to characterize chemical elements based on their position in the Periodic Table D.I. Mendeleev according to a specific plan.

Explanations for work:

Mendeleev's periodic system is a natural classification of chemical elements according to the electronic structure of their atoms. The electronic structure of an atom, and therefore the properties of an element, is judged by the position of the element in the corresponding period and subgroup of the per system. The patterns of filling the electrical levels explain the different number of elements in the periods. The strict periodicity of the arrangement of elements in Mendeleev’s first system of chemical elements is fully explained by the sequential nature of the filling of energy levels. The theory of atomic structure explains the periodic changes in the properties of elements. An increase in the positive charges of atomic nuclei from 1 to 107 determines the periodic repetition of the structure of the external energy level. And since the properties of elements mainly depend on the number of electrons in the outer level, they also repeat periodically. This is the physical meaning of the periodic law. In small periods, with an increase in the positive charge of atomic nuclei, the number of electrons at the external level (from 1 to 2 in the first period, and from 1 to 8 in the second and third periods), which explains the change in the properties of elements: at the beginning of the period (except for the first period) there is an alkali metal, then the metallic properties gradually weaken and the properties of the nonmetal increase. In large periods, as the charge of the nuclei increases, the filling of levels with electrons is more difficult, which also explains the more complex change in the properties of elements compared to elements of small periods. Thus, in even rows of large periods, with increasing charge, the number of electrons in the outer level remains constant and is equal to 2 or 1. Therefore, while the level next to the outer (second outer) is filled with electrons, the properties of the elements in these rows change extremely slowly. Only in odd rows, when the number of electrons in the outer level increases with increasing nuclear charge (from 1 to 8), the properties of elements begin to change in the same way as those of typical ones. In the light of the doctrine of the structure of atoms, the division of D.I. Mendeleev of all elements into 7 periods. The period number corresponds to the number of atomic energy levels filled with electrons. Therefore, s-elements are present in all periods, p-elements in the second and subsequent periods, d-elements in the fourth and subsequent periods, and f-elements in the sixth and seventh periods. The division of groups into subgroups, based on the difference in the filling of energy levels with electrons, is also easy to explain. For elements of the main subgroups, either s-sublevels (these are s-elements) or p-sublevels (these are p-elements) of external levels are filled. For elements of side subgroups, the (d-sublevel of the second outside level (these are d-elements) is filled. For lanthanides and actinides, the 4f- and 5f-sublevels are filled, respectively (these are f-elements). Thus, each subgroup combines elements whose atoms have similar structure of the external electronic level. In this case, the atoms of the elements of the main subgroups contain at the external levels a number of electrons equal to the number of the group. The secondary subgroups include elements whose atoms have two or one electrons at the external level. Differences in the structure also determine the differences in. properties of elements of different subgroups of the same group. Thus, at the external level of the atoms of the elements of the halogen subgroup there are seven electrons of the manganese subgroup - the first are typical metals, and the second are metals. But the elements of these subgroups also have common properties: they enter into chemical ones. reactions, all of them (with the exception of fluorine F) can donate 7 electrons to the formation of chemical bonds, while the atoms of the manganese subgroup donate 2 electrons from the outer level and 5 electrons from the next level. Thus, for elements of side subgroups, the valence electrons are not only the outer ones, but also the penultimate (second outer) levels, which is the main difference in the properties of the elements of the main and side subgroups. It also follows that the group number, as a rule, indicates the number of electrons that can participate in the formation of chemical bonds. This is the physical meaning of the group number. So, the structure of atoms determines two patterns: 1) a change in the properties of elements horizontally - in the period from left to right, metallic properties are weakened and non-metallic properties are strengthened; 2) a change in the properties of elements vertically - in a subgroup, with increasing atomic number, metallic properties are strengthened and non-metallic properties are weakened. In this case, the element (and the cell of the system) is located at the intersection of the horizontal and vertical, which determines its properties. This helps to find and write the properties of elements whose isotopes are obtained artificially. Based on the number of energy levels in the electron shell of an atom, elements are divided into seven periods.

The first period consists of atoms in which the electron shell consists of one energy level, in the second period - of two, in the third - of three, in the fourth - of four, etc. Each new period begins when a new energy level begins to be filled level. In the periodic system, each period begins with elements whose atoms at the outer level have one electron - atoms of alkali metals - and ends with elements whose atoms at the outer level have 2 (in the first period) or 8 electrons (in all subsequent periods) - atoms of noble gases . The outer electron shells are similar for atoms of elements (Li, Na, K, Rb, Cs); (Be, Mg, Ca, Sr); (F, Cl, Br, I); (He, Ne, Ar, Kr, Xe), etc. That is why each of the above groups of elements appears in a certain main subgroup of the periodic table: Li, Na, K, Rb, Cs in group I, F, Cl, Br, I - in VII, etc. It is due to the similarity in the structure of the electronic shells of atoms that their physical and chemical properties are similar. The number of main subgroups is determined by the maximum number of elements at the energy level and is equal to 8. The number of transition elements (elements of side subgroups) is determined by the maximum number of electrons at the d-sublevel and is equal to 10 in each of the major periods. Since in Mendeleev’s periodic system of chemical elements one of the side subgroups contains three transition elements with similar chemical properties (the so-called triads Fe-Co-Ni, Ru-Rh-Pd, Os-Ir-Pt), then the number of side subgroups is as well as the main ones, is equal to 8. By analogy with transition elements, the number of lanthanides and actinides placed at the bottom of the periodic system in the form of independent series is equal to the maximum number of electrons at the f-sublevel, i.e. 14. The period begins with an element in whose atom there are The outer level contains one s-electron: in the first period it is hydrogen, in the rest - alkali metals. The period ends with a noble gas: the first is helium (1s2), the remaining periods are elements whose atoms at the external level have the electronic configuration ns2np6. The first period contains two elements: hydrogen (Z=1) and helium (Z= 2). The second period begins with the element lithium (Z = 3) and ends with neon (Z = 10). The second period has eight elements. The third period begins with sodium (Z= 11), the electron configuration of which is 1s22s22p63s1. The filling of the third energy level began with it. It ends at the inert gas argon (Z = 18), the 3s and 3p sublevels of which are completely filled. Electronic formula of argon: 1s22s22p6Зs23p6. Sodium is an analogue of lithium, argon is neon. In the third period, as in the second, there are eight elements. The fourth period begins with potassium (Z= 19), the electronic structure of which is expressed by the formula 1s22s22p63s23p64s1. Its 19th electron occupied the 4s sublevel, the energy of which is lower than the energy of the 3d sublevel. The outer 4s electron gives the element properties similar to those of sodium. In calcium (Z = 20), the 4s sublevel is filled with two electrons: 1s22s22p63s23р64s2. The filling of the 3d sublevel begins with the element scandium (Z = 21), since it is energetically more favorable than the 4p sublevel. Five orbitals of the 3d sublevel can be occupied by ten electrons, which is the case for atoms from scandium to zinc (Z = 30). Therefore, the electronic structure of Sc corresponds to the formula 1s22s22p63s23p63d14s2, and that of zinc - 1s22s22p63s23p63d104s2. In the atoms of subsequent elements up to the inert gas krypton (Z = 36), the 4p sublevel is filled. The fourth period has 18 elements. The fifth period contains elements from rubidium (Z = 37) to the inert gas xenon (Z = 54). Their energy levels are filled in the same way as for the elements of the fourth period: after Rb and Sr, ten elements from yttrium (Z = 39) to cadmium (Z=48) the 4d sublevel is filled, after which electrons occupy the 5p sublevel. In the fifth period, as in the fourth, there are 18 elements. In the atoms of the sixth period elements cesium (Z = 55) and barium (Z = 56), the 6s sublevel is filled. In lanthanum (Z = 57), one electron enters the 5d sublevel, after which the filling of this sublevel stops, and the 4f level begins to be filled, the seven orbitals of which can be occupied by 14 electrons. This occurs in atoms of lanthanide elements with Z = 58 - 71. Since the deep 4f sublevel of the third level outside is filled in these elements, they have very similar chemical properties. From hafnium (Z = 72), the filling of the d sublevel resumes and ends at mercury (Z = 80), after which electrons fill the 6p sublevel. The filling of the level is completed at the noble gas radon (Z= 86). There are 32 elements in the sixth period. The seventh period is unfinished. The filling of electronic levels with electrons is similar to the sixth period. After filling the 7s sublevel of France (Z = 87) and radium (Z = 88), an actinium electron enters the 6d sublevel, after which the 5f sublevel begins to be filled with 14 electrons. This occurs in atoms of actinide elements with Z = 90 - 103. After the 103rd element, the b d-sublevel is filled: in kurchatovium (Z = 104), nielsborium (Z = 105), elements Z = 106 and Z = 107. Actinides, like lanthanides, have many similar chemical properties. Although the 3 d-sublevel is filled in after the 4s-sublevel, it is placed earlier in the formula, since all sublevels of a given level are written sequentially. Depending on which sublevel is last filled with electrons, all elements are divided into four types (families). 1. s-elements: the s-sublevel of the outer level is filled with electrons. These include the first two elements of each period. 2. p-elements: the p-sublevel of the outer level is filled with electrons. These are the last 6 elements of each period (except the first and seventh). 3. d-elements: the d-sublevel of the second outside level is filled with electrons, and one or two electrons remain on the outer level (Pd has zero). These include elements of inserted decades of large periods located between the s- and p-elements (they are also called transition elements). 4. f-elements: the f-sublevel of the third outside level is filled with electrons, and two electrons remain at the outer level. These are lanthanides and actinides. In the periodic table there are 14 s-elements, 30 p-elements, 35 d-elements, 28 f-elements. Elements of the same type have a number of common chemical properties.

Let's consider the characteristics of a chemical element-metal according to its position in the periodic table, using lithium as an example.

Lithium is an element of period 2 of the main subgroup of group I of the periodic system of D.I. Mendeleev, element IA or subgroup of alkali metals.

The structure of the lithium atom can be reflected as follows: 3Li - 2ē, 1ē. Lithium atoms will exhibit strong reducing properties: they will easily give up their only external electron and as a result will receive an oxidation state (s.o.) of +1. These properties of lithium atoms will be less pronounced than those of sodium atoms, which is associated with an increase in the radii of the atoms: Rat (Li)< Rат (Na). Восстановительные свойства атомов лития выражены сильнее, чем у бериллия, что связано и с числом внешних электронов, и с расстоянием от ядра до внешнего уровня.

Lithium is a simple substance, it is a metal, and, therefore, has a metal crystal lattice and a metal chemical bond. The charge of the lithium ion is not Li+1 (as indicated by the s.o.), but Li+. General physical properties of metals arising from their crystalline structure: electrical and thermal conductivity, malleability, ductility, metallic luster, etc.

Lithium forms an oxide with the formula Li2O - this is a salt-forming, basic oxide. This compound is formed due to the ionic chemical bond Li2+O2-, interact with water, forming an alkali.

Lithium hydroxide has the formula LiOH. This base is alkali. Chemical properties: interaction with acids, acid oxides and salts.

In the subgroup of alkali metals there is no general formula “Volatile hydrogen compounds”. These metals do not form volatile hydrogen compounds. Compounds of metals with hydrogen are binary compounds of the ionic type with the formula M+H-.

Characteristics of chemical elements based on their position in the Periodic Table

Practical work report 4.

Student______________________________________________________________________

Group_______

Purpose of the work:

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

1. element:______________________________________________________________

2. Position in the Periodic Table:

2.1. Item No.____

2.2. Period number____

2.3. Group number____

2.4. Subgroup____

3. Atomic composition:

3.1. Core charge_____

3.2. Number protons in the core____

3.3. Number neutrons in the core____

3.4. Total number electrons in an electronic shell_____

3.5. Number of Energy Levels_____