Chemistry lesson
in 9th grade on the topic:
“Periodic law and periodic system of D.I.Mendeleev”
Completed by: teacher of chemistry, biology
Korshunova Svetlana Valerievna
p. Golyshmanovo 2015
Topic: Periodic law and periodic system of D.I.Mendeleev
Target: To give students an idea of D.I. Mendeleev’s law and the structure of his periodic system, to identify the significance of this law for the development of chemistry and understanding the scientific picture of the world as a whole.
Tasks:Educational.
To develop knowledge about the periodic law and the periodic system of D.I. Mendeleev.
Teach students to work with the periodic system (be able to determine the position of an element in the periodic system, the properties of an element depending on its position in the periodic system).
Continue developing the ability to work with a textbook and notebook. Developmental.
Develop observation skills and memory (when studying the physical meaning of the periodic law and its graphic display).
Develop the ability to compare (for example, comparing the properties of elements depending on their position in the periodic table).
Teach students to generalize and draw conclusions. Educational.
Continue to form students’ worldview based on ideas about the meaning of D.I. Mendeleev’s law. Lesson type: learning new material
Lesson format: working with informational text
Methods:1. Perceptual aspect (aspect of perception): visual - practical methods.
2. Logical aspect (mental operations when submitting and assimilating educational material); deductive methods (from general to specific); systematization of knowledge.
3. gnostic aspect (cognition); heuristic (partially search) method.
4. Management aspect (degree of student independence); independent learning activities. Communication channels: student - literary source; student - student; student - teacher.
Equipment: system chemical elements D.I. Mendeleev, presentation on the topic of the lesson.
During the classes:
Epigraph on the board.“The future does not threaten the periodic law with destruction, but only superstructure and development are promised” (D.I. Mendeleev)
Lesson steps All students are given a text in which they must try to find answers to the questions they themselves have posed. About 15 minutes are allotted for working with the text, after which the teacher returns to the questions written on the board and asks the children to answer them. (application)Then the children are given the task of composing a new story, but based on what they read. You can only hear one answer, and ask the children to add to it. Control testing. Students independently answer test tasks for 5–7 minutes, which are printed in advance and distributed to everyone on the table. 1. Alkali metals include the following elements:
a) Na; b) Al; c) Ca; d) Li. 2. Sodium is stored under a layer:
a) kerosene; b) water; c) sand; d) gasoline. 3. The most active among the elements:
a) Li; b) Na; c) Cs; d) K. 4. Medium typical for NaOH solution:
a) sour; b) alkaline; c) neutral. 5. Match:
Alkali metal
6. Match:Oxide
7. Halogens include:a) Cl; b) Mn; c) Br; d) Re. 8. Select an environment specific to aqueous solution HCl:
a) alkaline; b) sour; c) neutral. 9. D.I. Mendeleev based the classification of elements on:
a) mass; b) density; c) temperature. 10. Complete the sentence:
“D.I. Mendeleev arranged the elements in order...” 11. The list of chemical elements includes Al, P, Na, C, Cu:
a) metals; b) non-metals. 12. Small periods are:
a) 1; b) 2; at 5; d) 7. 13. The main subgroup of group I includes:
a) Na; b) Cu; c) K; d) Li. 14. In the main subgroup with decreasing serial number, metallic properties:
a) intensify; b) weaken; c) do not change. Those students who actively worked when checking tests and answered them correctly are given high marks.
Periodic law and periodic system D.I. Mendeleev
Dmitry Mendeleev was born on February 8, 1834 in Tobolsk in the family of the director of the gymnasium and trustee of public schools of the Tobolsk province Ivan Pavlovich Mendeleev and Maria Dmitrievna Mendeleeva, née Kornilieva.
In the fall of 1841, Mitya entered the Tobolsk gymnasium. After graduating from high school in his hometown, Dmitry Ivanovich entered St. Petersburg at main pedagogical institute, after graduating from which he went to two years on a scientific trip abroad. After his return he was invited to St. Petersburg University. When starting to lecture on chemistry, Mendeleev did not find nothing that could be recommended to students as teaching aid. And he I decided to write a new book - “Fundamentals of Chemistry”.The discovery of the periodic law was preceded by 15 years of hard work. At the time of the discovery of the periodic law, 63 chemical elements were known, about 50 existed various classifications. Most scientists compared only elements with similar properties, so they were unable to discover the law. Mendeleev compared everything with each other, including dissimilar elements. The main characteristic of the atom when constructing the periodic table was accepted his atomic mass. D.I. Mendeleev discovered a periodic change in the properties of elements with changes in the values of their atomic masses, comparing dissimilar natural groups of elements with each other. At that time, such groups of elements as, for example, halogens, alkali and alkaline earth metals were known. Mendeleev wrote out and compared the elements of these groups in the following way, arranging them in order of increasing atomic mass values.All this made it possible for D.I. Mendeleev to call the law he discovered “the law of periodicity” and formulate it as follows: “the properties of simple bodies, as well as the forms and properties of compounds of elements are in periodic dependence (or, expressed algebraically, form a periodic function) on the value atomic weights of elements. In accordance with this law, the periodic system of elements was compiled, which objectively reflects the periodic law. The entire series of elements, arranged in order of increasing atomic masses, is divided by D. I. Mendeleev into periods. Within each period, the properties of elements change naturally (for example, from alkali metal to halogen). By placing periods in such a way as to highlight similar elements, D. I. Mendeleev created the periodic system of chemical elements. At the same time, the atomic masses of a number of elements were corrected, and for 29 elements that had not yet been discovered, empty spaces (dashes) were left.
The periodic table of elements is a graphical (tabular) representation of the periodic law
The date of the discovery of the law and the creation of the first version of the periodic system is March 1, 1869. D. I. Mendeleev worked on improving the periodic system of elements until the end of his life.Currently, more than 500 variants of the periodic table are known; This various shapes transmission of the periodic law.
In the periodic system, there are 7 periods horizontally (indicated by Roman numerals), of which I, II and III are called minor, and IV, V, VI and VII are called major. All elements of the periodic table are numbered in the order in which they follow each other. The element numbers are called ordinal or atomic numbers.
There are eight groups arranged vertically in the periodic table (indicated by Roman numerals). The group number is associated with the degree of oxidation of the elements that they exhibit in compounds. Typically, the highest positive oxidation state of an element is equal to the group number. The exception is fluorine - its oxidation state is -1; copper, silver, gold exhibit oxidation states of +1, +2 and +3; Of the Group VIII elements, the oxidation state +8 is known only for osmium, ruthenium and xenon.
Each group is divided into two subgroups - home And side, which in the periodic table is emphasized by the displacement of some to the right and others to the left.The properties of elements in subgroups naturally change: from top to bottom, metallic properties increase and non-metallic properties weaken. Obviously, the metallic properties are most pronounced in francium, then in cesium; non-metallic - for fluorine, then - for oxygen.
Arranged horizontally in the table, and eight groups arranged vertically.
A period is a horizontal series of elements, beginning (with the exception of the 1st period) with an alkali metal and ending with an inert (noble) gas.
The 1st period contains 2 elements, the 2nd and 3rd periods - 8 elements each. The first, second and third periods are called small (short) periods.
The 4th and 5th periods each contain 18 elements, the 6th period contains 32 elements, the 7th period contains elements from the 87th onwards, up to the last currently known element. The fourth, fifth, sixth and seventh periods are called large (long) periods.
Group – this is a vertical row of elements.
Each group of the periodic system consists of two subgroups: the main subgroup (A) and the secondary subgroup (B). Main subgroup contains elements of small and large periods (metals and non-metals). Side subgroup contains elements only of long periods (metals only).
For example, the main subgroup of Group I consists of the elements lithium, sodium, potassium, rubidium, cesium and francium, and the secondary subgroup of Group I consists of the elements copper, silver and gold. The main subgroup of group VIII is formed by inert gases, and the secondary subgroup is formed by the metals iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, hasium and meitnerium .
The properties of simple substances and compounds of elements change monotonically in each period and abruptly at the boundaries of periods. This nature of the change in properties is the meaning of the periodic dependence. In periods from left to right, the non-metallic properties of the elements monotonically increase, and the metallic properties decrease. For example, in the second period: lithium is a very active metal, beryllium is a metal that forms an amphoteric oxide and, accordingly, an amphoteric hydroxide, B, C, N, O are typical non-metals, fluorine is the most active non-metal, neon is an inert gas. Thus, at the boundaries of the period, the properties change abruptly: the period begins with an alkali metal and ends with an inert gas.
In periods from left to right, the acidic properties of the oxides of elements and their hydrates increase, and the basic ones weaken. For example, in the third period, the oxides of sodium and magnesium are basic oxides, aluminum oxide is amphoteric, and the oxides of silicon, phosphorus, sulfur and chlorine are acidic oxides. Sodium hydroxide is a strong base (alkali), magnesium hydroxide is a weak insoluble base, aluminum hydroxide is an insoluble amphoteric hydroxide, silicic acid is a very weak acid, phosphoric acid is a medium strength acid, sulfuric is a strong acid, perchloric acid is the strongest acid in this series.
In the main subgroups, from top to bottom, the metallic properties of the elements increase, and the non-metallic properties weaken. For example, in subgroup 4A: carbon and silicon are non-metals, germanium, tin, lead are metals, and tin and lead are more typical metals than germanium. In subgroup 1A, all elements are metals, but chemical properties can also be traced to an increase in metallic properties from lithium to cesium and francium. As a result, metallic properties are most pronounced in cesium and francium, and nonmetallic properties are most pronounced in fluorine.
In the main subgroups, from top to bottom, the basic properties of oxides and their hydrates increase, and the acidic ones weaken. For example, in subgroup 3A: B 2 O 3 – acid oxide, and T1 2 O 3 is the main one. Their hydrates: H 3 VO 3 is an acid, and T1(OH) 3 is a base.
The structure of the atom. Modern formulation of the Periodic
law
Later, in 1913, the English physicist G. Moseley established that the charge of the nucleus is numerically equal to the serial number of the element in the periodic table. Thus, atomic nuclear charge – main characteristic chemical element. Chemical element –is a set of atoms with the same nuclear charge.
This leads to the modern formulation of the periodic law: properties of elements, as well as the properties of the simple and complex substances are periodically dependent on the charge of the nuclei of their atoms.
In four places on the Periodic Table, elements “violate” the strict order of arrangement in increasing atomic mass. These are pairs of elements:
18 Ar(39.948) – 19 K (39.098);
27 Co(58.933) – 28 Ni(58.69);
52 Te(127.60) – 53 I(126.904);
90 Th(232.038) – 91 Pa(231.0359).
During the time of D.I. Mendeleev, such deviations were considered shortcomings Periodic table. The theory of atomic structure put everything in its place. In accordance with the nuclear charge values, these elements were placed correctly by Mendeleev in the system. Thus, having violated in these cases the principle of placing elements in order of increasing atomic masses and being guided by the physical and chemical properties of the elements, Mendeleev actually used a more fundamental characteristic of the element - its serial number in the system, which turned out to be equal to the charge of the nucleus.
Classical mechanics could not explain many experimental facts concerning the behavior of the electron in an atom. So, according to ideas classical theory In electrodynamics, a system consisting of a charge rotating around another charge would radiate energy, causing the electron to eventually fall into a nucleus. The need arose to create a different theory that would describe the behavior of objects in the microworld, for the description of which classical Newtonian mechanics is insufficient.
The basic laws of such a theory were formulated in 1923 - 1927. and it was called quantum mechanics.
Quantum mechanics is based on three main principles.
Particle-wave dualism (microparticles simultaneously exhibit both wave and material properties, i.e., a dual nature).
The principle of energy quantization (microparticles emit energy not constantly, but discretely in separate portions - quanta).
In 1913, N. Bohr used quantum theory to explain the spectrum of atomic hydrogen, suggesting that electrons in atoms can only be in certain “allowed” orbits corresponding to certain energy values. Bohr also suggested that, while in these orbits, the electron does not emit energy. Therefore, until the electrons in an atom make transitions from one orbit to another, the energy of the atom remains constant. When an electron moves from one orbit to another, a quantum of radiant energy is emitted, the value of which is equal to the difference in energy corresponding to these orbits.
The laws of the microworld are determined by their statistical nature. The position of an electron in an atom is uncertain. This means that it is impossible to simultaneously accurately determine both the speed of the electron and its coordinates in space.
Figure 1.1 – Electron cloud of the hydrogen atom
The shape and size of the electron cloud can vary depending on the energy of the electron.
There is the concept of “orbital”, which is understood as a set of positions of an electron in an atom.
Each orbital can be described by the corresponding wave function - atomic orbital , depending on three integer parameters called quantum numbers .
Quantum mechanical description of the state of an electron in an atom
Sometimes used letter designations principal quantum number, i.e. each numerical value P denoted by the corresponding letter of the Latin alphabet:
The principal quantum number determines the energy of the electron and the size of the electron cloud, i.e. the average distance of an electron from the nucleus. The more P, the higher the electron energy, therefore, the minimum energy corresponds to the first level ( P= 1).
In the Periodic Table of Elements, the maximum value of the principal quantum number corresponds to the period number.
2. Orbital orside quantum number ( l ) characterizes the energy sublevel and determines the shape of the electron cloud; accepts integer values from 0 to (P-1). Its meanings are usually indicated by letters:
| l= | 0 | 1 | 2 | 3 |
| s | p | d | f |
Number of possible values l corresponds to the number of possible sublevels at a given level, equal to the level number (P).
| At | n=1 | l=0 | (1 value) |
| n=2 | l=0, 1 | (2 values) |
|
| n=3 | l=0, 1, 2 | (3 values) |
|
| n=4 | l=0, 1, 2, 3 | (4 values) |
The energy of electrons at different sublevels of the same level varies depending on l as follows: for each value l corresponds to a certain shape of the electron cloud: s- sphere, R– three-dimensional figure eight, d And f– three-dimensional four-petal rosette or a more complex shape (Figure 1.2).
| | | | |
| | | | |
Figure 1.2, sheet 1 – Electron clouds s-, p- And d-atomic orbitals
| | | | | |
| | | | | |
Figure 1.2, sheet 2 – Electron clouds s-, p- And d-atomic orbitals
3. Magnetic quantum number (
m
l
)
characterizes the orientation of the electron cloud in a magnetic field; takes integer values from – l before +
l:
m l = –l, ...,
0, ..., +
l(Total 2
l + 1
values).
At l= 0 (s-electron) m l can take only one value (for a spherical electron cloud, only one orientation in space is possible).
At l = 1 (R-electron) T 1 can take 3 values (three orientations of the electron cloud in space are possible).
At l = 2 (d-electron) are possible 5 values m l; (different orientations in space with a slightly changing shape of the electron cloud).
At l = 3 (f-electron) 7 possible values m l(the orientation and shape of the electron clouds is not very different from that observed in d-electrons).
Electrons having the same values P,l And m l, are in the same orbital. Thus, orbital – this is the state of an electron, characterized by a certain set of three quantum numbers: n, l And m l , which determine the size, shape and orientation of the electron cloud. Number of values it can take m l, at given value l, equal to the number of orbitals at a given sublevel.
4. Spin quantum number (t s ) characterizes the intrinsic angular momentum (spin) of an electron (not associated with motion around the nucleus), which in the form of a loose model can be considered corresponding to the direction of rotation of the electron around its axis. It can take two values: – 1/2 and + 1/2, corresponding to two opposite directions of the magnetic moment.
Electrons that have the same values of the principal, orbital and magnetic quantum numbers and differ only in the values of the spin quantum number are in the same orbital and form one common electron cloud. Such two electrons having opposite spins and located in the same orbital are called paired. One electron per orbital is unpaired.
Thus, the state of an electron in an atom is determined by a set of values of four quantum numbers.
Lecture 2
Questions
Formation of the electron shell of an atom.
Electronic configurations of atoms
Electronic configuration of the atom and the periodic table
Formation of the electron shell of an atom
Minimum energy principle : filling atomic orbitals with electrons ( A.O. ) occurs in increasing order of their energy. In a steady state, electrons are at the lowest energy levels and sublevels.
This means that each new electron in the atom falls into the lowest (in terms of energy) free sublevel.
Let us characterize the levels, sublevels and orbitals by the electron energy reserve. For a multielectron atom, the energy of orbitals at levels and sublevels changes as follows:
1s s р s р s d р s d р s d (4 f) p s d (5 f) R
For complex atoms it works rule
(p+
l
)
or Klechkovsky's rule
:
AO energy increases in accordance with the increase in the amount (p+l)
principal and orbital quantum numbers. At the same value of the sum, the energy is lower for the AO with a lower value of the principal quantum number.
Pauli principle : An atom cannot have two electrons with the same values of all four quantum numbers.
Each orbital is an energy state that is characterized by the values of three quantum numbers: P,l And m l These numbers determine the size, shape, and orientation of the orbital in space. Consequently, there can be no more than two electrons in one orbital and they will differ in the value of the fourth (spin) quantum number: T s= + 1 / 2 or – 1 / 2 (table 2.1)
For example, for 1 s- orbitals there are two sets of quantum numbers:
| n | 1 | 1 |
| l | 0 | 0 |
| m l | 0 | 0 |
| m s | + 1 / 2 | – 1 / 2 |
Therefore, there can only be two electrons with different spin numbers here.
For each of the three 2 p-
orbitals there are also only two possible sets of quantum numbers:
| n | 2 | 2 |
| l | 1 | 1 |
| m l | 0 | 0 |
| m s | + 1 / 2 | – 1 / 2 |
So, on R-sublevel can only contain six electrons.
The largest number of electrons at an energy level is:
Where P– level number, or main quantum number.
Consequently, the first energy level can contain no more than two electrons, the second – no more than 8, the third – no more than 18, and the fourth – no more than 32 (Table 2.1).
Table 2.1 – Formation of the electron shell of an atom
| Energy level n | l | m l | m s | Number of electrons |
|
| at sublevel | at the level |
||||
| 1 | 0 (s) | 0 | ±1/2 | 2 | 2 |
| 2 | 0 (s) | 0 | ±1/2 | 2 | 8 |
| 1 (p) | –1, 0, 1 | ±1/2 | 6 |
||
| 3 | 0 (s) | 0 | ±1/2 | 2 | 18 |
| 1 (p) | –1, 0, 1 | ±1/2 | 6 |
||
| 2 (d) | –2, –1, 0, 1, 2 | ±1/2 | 10 |
||
| 4 | 0 (s) | 0 | ±1/2 | 2 | 32 |
| 1 (p) | –1, 0, 1 | ±1/2 | 6 |
||
| 2 (d) | –2, –1, 0, 1, 2 | ±1/2 | 10 |
||
| 3 (f) | –3, –2, –1, 0, 1, 2, 3 | ±1/2 | 14 |
||
Hund's rule : When an electronic sublevel is formed, electrons fill the maximum number of free orbitals so that the number of unpaired electrons is greatest.
Electronic configurations of atoms
The electronic configuration of an atom is depicted in two ways - in the form of electronic formulas and electron diffraction diagrams. When writing electronic formulas, the principal and orbital quantum numbers are used. The sublevel is designated using the principal quantum number (number) and the orbital quantum number (corresponding letter). The number of electrons in a sublevel is characterized by the superscript. For example, for the ground state of the hydrogen atom the electronic formula is: 1 s 1 .
The structure of electronic levels can be more fully described using electron diffraction diagrams, where the distribution of electrons among sublevels is represented in the form of quantum cells. In this case, the orbital is conventionally depicted as a square with a sublevel designation next to it. The sublevels at each level should be slightly offset in height, since their energy is slightly different. Electrons are designated by arrows depending on the sign of the spin quantum number. Electron diffraction diagram of a hydrogen atom:
| 1s | |
The principle of constructing electronic configurations of multi-electron atoms is to add protons and electrons to the hydrogen atom. The distribution of electrons across energy levels and sublevels obeys the rules discussed earlier.
Taking into account the structure of the electronic configurations of atoms, all known elements, in accordance with the value of the orbital quantum number of the last filled sublevel, can be divided into four groups: s-elements,
R-elements, d-elements, f-elements.
s-orbitals are called s-elements. Elements whose atoms are the last to be filled
p-orbitals are called p-elements. Elements whose atoms are the last to be filled d-orbitals are called d-elements. Elements whose atoms are the last to be filled f-orbitals are called f-elements.
In the helium atom He (Z = 2), the second electron occupies the l s orbital, its electronic formula: 1 s 2. Electron diffraction diagram:
| 1s | ↓ |
Helium ends the first shortest period of the Periodic Table of Elements. The electronic configuration of helium is designated [He].
The second period is opened by lithium Li (Z = 3), its electronic formula:
[Not] 2 s 1 .
Electron diffraction diagram:
| | 2p | ||
| 2s |
After lithium comes beryllium Be (Z = 4), in which an additional electron populates 2 s-orbital. Electronic formula of Be: 2 s 2
| ↓ | ||||
| 2s | 2p |
In the ground state, the next electron of boron B (Z = 5) occupies
2R-orbital, V: l s 2 2s 2 2p 1 ; its electron diffraction diagram:
| ↓ | | |||
| 2s | 2p |
The following five elements have electronic configurations:
| C(Z=6):2 s 2 2p 2 | N(Z=7):2 s 2 2p 3 |
|||||||||
| ↓ | | | ↓ | | | |
||||
| 2s | 2p | 2s | 2p | |||||||
| O(Z=8):2 s 2 2p 4 | F(Z=9):2 s 2 2p 5 |
|||||||||
| ↓ | ↓ | | | ↓ | ↓ | ↓ | |
|||
| 2s | 2p | 2s | 2p | |||||||
| Ne(Z=10):2 s 2 2p 6 | ||||||||||
| ↓ | ↓ | ↓ | ↓ | |||||||
| 2s | 2p | |||||||||
The given electronic configurations are determined by Hund's rule.
The first and second energy levels of neon are completely filled. Let us denote its electronic configuration and will use it in the future for brevity in writing the electronic formulas of atoms of elements.
Sodium Na (Z = 11) and Mg (Z = 12) open the third period. Outer electrons occupy 3 s-orbital:
| Na (Z=11): 3 s 1 |
||||||||||
| | ||||||||||
| 3s | 3p | 3d | ||||||||
| Mg (Z=12): 3 s 2 |
||||||||||
| ↓ | ||||||||||
| 3s | 3p | 3d | ||||||||
Then, starting with aluminum (Z = 13), 3 is filled p-sublevel. The third period ends with argon Ar (Z= 18):
| Al (Z=13): 3 s 2 3p 1 |
||||||||||
| ↓ | | |||||||||
| 3s | 3p | 3d | ||||||||
| |
||||||||||
| Ar (Z=18): 3 s 2 3p 6 |
||||||||||
| ↓ | ↓ | ↓ | ↓ | |||||||
| 3s | 3p | 3d | ||||||||
The elements of the third period differ from the elements of the second in that they have free 3 d-orbitals that can participate in the formation of a chemical bond. This explains the valence states exhibited by elements.
In the fourth period, in accordance with the rule (n +l), potassium K (Z = 19) and calcium Ca (Z = 20) have 4 electrons s–sublevel, not 3 d.Starting with scandium Sc (Z = 21) and ending with zinc Zn (Z = 30), filling occurs
3d-sublevel:
Sc: 4 s 2 3d 1 → Zn: 4 s 2 3d 10
The electronic formulas of d-elements can be presented in a different form: the sublevels are listed in increasing order of the main quantum number, and at a constant P– in order of increasing orbital quantum number. For example, for Zn such an entry would look like this: 3 d 10 4s 2 .
Both of these entries are equivalent, but the electronic formula of zinc given earlier correctly reflects the order in which the sublevels are filled.
In row 3 d-elements in chromium Cr (Z = 24) there is a deviation from the rule (n +l).
In accordance with this rule, the electronic configuration of Cr should look like this: [Ar] 3 d 4 4s 2. It has been established that its actual configuration is
3d 5 4s 1 .
This effect is sometimes called electron "dip".
Deviations from the rule (n +l) are also observed in other elements (Table 2.2). This is due to the fact that as the principal quantum number increases, the differences between the energies of sublevels decrease.
Next comes filling 4 R-sublevel (Ga – Kg). The fourth period contains only 18 elements. Filling 5 occurs in the same way s-, 4d-And
5R-sublevels of 18 elements of the fifth period. Note that the energy is 5 s-And
4d-sublevels are very close, and the electron with 5 s-sublevels can easily move to 4 d-sublevel. At 5 s-sublevel Nb, Mo, Tc, Ru, Rh, Ag has only one electron. In ground state 5 s-Pd sublevel is not filled. A “failure” of two electrons is observed.
Table 2.2 – Electronic configuration of elements with deviation
from Klechkovsky's rule
| 1 | 1 | 3 |
| Cr (Z=24) | 4s 2 3d 4 | 4s 1 3d 5 |
| Cu (Z=29) | 4s 2 3d 9 | 4s 1 3d 10 |
| Nb (Z=41) | 5s 2 4d 3 | 5s 1 4d 4 |
| Mo (Z=42) | 5s 2 4d 4 | 5s 1 4d 5 |
| Tc (Z=43) | 5s 2 4d 5 | 5s 1 4d 6 |
| Ru (Z=44) | 5s 2 4d 6 | 5s 1 4d 7 |
| Rh (Z=45) | 5s 2 4d 7 | 5s 1 4d 8 |
| Pd (Z=46) | 5s 2 4d 8 | 5s 0 4d 10 |
| Ag (Z=47) | 5s 2 4d 9 | 5s 1 4d 10 |
| La (Z=57) | 6s 2 4f 1 5d 0 | 6s 2 4f 0 5d 1 |
| Ce (Z=58) | 6s 2 4f 2 5d 0 | 6s 2 4f 1 5d 1 |
| Gd (Z=64) | 6s 2 4f 8 5d 0 | 6s 2 4f 7 5d 1 |
| Ir (Z=77) | 6s 2 4f 14 5d 7 | 6s 0 4f 14 5d 9 |
| Pt (Z=78) | 6s 2 4f 14 5d 8 | 6s 1 4f 14 5d 9 |
| Au (Z=79) | 6s 2 4f 14 5d 9 | 6s 1 4f 14 5d 10 |
In the sixth period, after filling the 6s sublevel of cesium Cs (Z = 55) and barium Ba (Z = 56), the next electron, according to the rule (n +l),
must take
4f-sublevel. However, in lanthanum La (Z = 57) the electron goes to 5 d-sublevel. Half filled (4 f 7) 4f-sublevel has increased stability, so gadolinium has Gd (Z = 64), next to europium Eu (Z = 63), by 4 f- the sublevel retains the same number of electrons (7), and a new electron arrives at 5 d-sublevel, breaking the rule (n +l).
In terbium Tb (Z = 65), the next electron occupies 4 f-sublevel and the electron transition occurs from
5d-sublevel (configuration 4 f 9 6s 2). Filling 4 f-sublevel ends at ytterbium Yb (Z = 70). The next electron of the lutetium atom Lu is occupied
5d-sublevel. Its electronic configuration differs from that of the lanthanum atom only in that it is completely filled 4 f-sublevel.
Currently, in the Periodic Table of Elements D.I. Mendeleev, under scandium Sc and yttrium Y, lutetium (and not lanthanum) is sometimes placed as the first d-element, and all 14 elements in front of it, including lanthanum, are placed in a special group lanthanides beyond the Periodic Table of Elements.
The chemical properties of elements are determined mainly by the structure of the outer electronic levels. Change in the number of electrons on the third outside 4 f-sublevel has little effect on chemical properties elements. Therefore all 4 f-elements are similar in their properties. Then in the sixth period the filling of 5 occurs d-sublevel (Hf – Hg) and 6 R-sublevel (Tl – Rn).
In the seventh period 7 s-sublevel is filled in francium Fr (Z = 87) and radium Ra (Z = 88). Sea anemone shows a deviation from the rule (n +l), and the next electron populates 6 d-sublevel, not 5 f. Next comes a group of elements (Th – No) with 5 being filled f-sublevels that form a family actinides .
In lawrencium Lr (Z = 103), a new electron arrives at 6 d-sublevel. This element is sometimes placed under lutetium in the Periodic Table. The seventh period is not completed. Elements starting from 104 are unstable and their properties are little known. Thus, with increasing nuclear charge, similar electronic structures are periodically repeated external levels. In this regard, one should expect periodic changes various properties elements.
Electronic configuration of the atom and the periodic table
Element serial number in the periodic table shows the charge of the nucleus of its atom and the number of electrons in the atom.
Period number corresponds to the number of energy levels in the electron shell of atoms of all elements of a given period. In this case, the period number coincides with the value of the main quantum number of the external energy level.
Group number corresponds, as a rule, to the number of valence electrons in the atoms of elements of a given group.
Valence electrons – these are electrons of the last energy levels. Valence electrons have maximum energy and are involved in the formation of chemical bonds between atoms in molecules.
In the atoms of elements of the main subgroups (A), all valence electrons are at the last energy level and their number is equal to the group number. In the atoms of elements of side subgroups (B), there are no more than two electrons at the last energy level, the remaining valence electrons are at the penultimate energy level. Total number valence electrons are also usually equal to the group number.
The foregoing shows that as the charge of the nucleus increases, there is a natural periodic repetition of similar electronic structures of elements, and, consequently, a repetition of their properties, depending on the structure of the electronic shell of the atoms.
Thus, in the periodic system, as the atomic number of an element increases, the properties of the atoms of the elements, as well as the properties of simple and complex substances formed by these elements, are periodically repeated, since similar configurations of valence electrons in atoms are periodically repeated. This is physical meaning of the periodic law.
Subject. Periodic law and periodic system D.I. Mendeleev
Target:
To form in students the idea that the objectively existing relationship between chemical elements and formed substances is subject to the periodic law and is reflected in the periodic system; consider the structure of the periodic system, form a concept about periods and groups;
Develop the ability to analyze information and draw conclusions, skills in using the Periodic Table to search for information about chemical elements and their properties;
Cultivate cognitive interest in the subject.
During the classes
II. Update background knowledge
Conversation
1. What is classification?
2. Which chemist attempted to classify chemical elements? What characteristics did they take as a basis?
3. What groups of chemical elements are you familiar with? Give them a brief description.(Alkali metals, alkaline earth metals, halogens, inert gases)
III. Learning new material
1. History of the discovery of the Periodic Law
In the last lesson we learned that in the middle of the 19th century. knowledge about chemical elements became sufficient, and the number of elements increased so much that a natural need arose in science to classify them. The first attempts to classify elements were unsuccessful. The predecessors of D.I. Mendeleev (I.V. Debereiner, J.A. Newlands, L.Yu. Meyer) did a lot to prepare for the discovery of the periodic law, but were unable to comprehend the truth.
They used one of two approaches to building the system:
1. Combining elements into groups based on the similarity of composition and properties of the substances they form.
2. Arrangement of chemical elements in order of increasing atomic mass.
But neither one nor the other approach led to the creation of a system that combines all the elements.
The problem of systematizing chemical elements also interested the young 35-year-old professor Pedagogical University DI. Mendeleev. In 1869, he worked on creating a textbook for students, “Fundamentals of Chemistry.” The scientist understood well that in order for students to better understand the variety of properties of chemical elements, these properties need to be systematized.
By 1869, 63 chemical elements were known, many of which had incorrect relative atomic masses.
Mendeleev arranged the chemical elements in increasing order of their atomic masses and noticed that the properties of the elements are repeated after a certain interval - a period, Dmitry Ivanovich arranged the periods one under the other, so that similar elements were located under each other - on the same vertical, so the periodic system was built elements.
As a result of painstaking work for 15 years to correct the atomic masses and valence of elements, as well as to clarify the location of yet undiscovered chemical elements, D.I. Mendeleev discovered a law which he called the Periodic Law.
The properties of chemical elements, simple substances, as well as the composition and properties of compounds are periodically dependent on the values of atomic masses.
March 1, 1869 (February 18, old style) - the date of the opening of the Periodic Law.
Unfortunately, at first there were very few supporters of the periodic law. There are many opponents, especially in Germany and England.
The discovery of the periodic law is a brilliant example of scientific foresight: in 1870, Dmitry Ivanovich predicted the existence of three then unknown elements, which he named ekasilicon, ekaaluminum and ekaboron. He was able to correctly predict the most important properties of new elements. And then, 5 years later, in 1875, the French scientist P.E. Lecoq de Boisbaudran, who knew nothing about the work of Dmitry Ivanovich, discovered a new metal, calling it gallium. In a number of properties and the method of discovery, gallium coincided with eka-aluminum predicted by Mendeleev. But his weight turned out to be less than predicted. Despite this, Dmitry Ivanovich sent a letter to France, insisting on his prediction.
The scientific world was stunned that Mendeleev's prediction of the propertiesekaaluminum
turned out to be so accurate. From this moment on, the periodic law begins to take hold in chemistry.
In 1879, L. Nilsson discovered scandium in Sweden, which embodied what Dmitry Ivanovich predictedekabor
.
In 1886, K. Winkler discovered germanium in Germany, which turned out to beecasilicium
.
But the genius of Dmitry Ivanovich Mendeleev and his discoveries are not only these predictions!
In four places of the periodic table, D. I. Mendeleev arranged the elements not in the order of increasing atomic masses:
Ar – K, Co – Ni, Te – I, Th – Pa
Back at the end of the 19th century, D.I. Mendeleev wrote that, apparently, the atom consists of other smaller particles. After his death in 1907, it was proven that the atom consists of elementary particles. The theory of atomic structure confirmed Mendeleev's correctness; rearrangements of these elements not in accordance with the increase in atomic masses are completely justified.
Graphic representation The periodic law is the periodic system of chemical elements. This is a brief summary of the entire chemistry of elements and their compounds.
2. Structure of the Periodic Table
There is a long and a short version of the table
Each element is located in a specific cell of the periodic table.
What information does it carry?(element symbol, serial number, element name, name simple substance, relative atomic mass)
The components of the table are periods and groups.
The teacher shows the period in the table and asks the students to formulate the definition themselves. Then we compare it with the definition in the textbook (p. 140).
A period is a horizontal series of chemical elements that begins with an alkali metal and ends with an inert element.
The teacher shows the group in the table and asks the students to formulate the definition themselves. Then we compare it with the definition in the textbook (p. 140).
Periods can be large or small.
Which periods are long? Small ones?
How do metallic properties change over a period from left to right? Are they strengthening or weakening? Why do you think so?
Metallic properties weaken from left to right in a period, therefore, non-metallic properties increase. We will learn the reason for this by studying the structure of the atom in subsequent lessons.
Which element has more pronounced metallic properties: Ag- Cd? Mg-Al?
Which element has more clearly expressed non-metallic properties: O-N? S-Cl?
A group is a vertical column of elements that contains elements with similar properties. (write in notebook)
The group is divided into the main one(A) and side (V).
The main subgroup includes elements of both small and large periods. As a side note, only big ones. Side subgroups contain only metal elements (transition metals)
Name the elements of the second group, the main subgroup.
Name the elements of the fifth group, a secondary subgroup.
Name the elements of the eighth group, the main subgroup. What are their names?
IV. Generalization and systematization of knowledge
V .Summarizing the lesson, assessing students' knowledge
V І . Homework
Attention! The site administration is not responsible for the content of methodological developments, as well as for the compliance of the development with the Federal State Educational Standard.
Explanatory note
This lesson is taught in the main course high school for 8th grade students in the 1st half of the year.
Relevance of lesson development based on the use of the website resource “The Most Unusual Periodic Table of Chemical Elements D.I. Mendeleev" is dictated by the requirements of the Federal State Educational Standard of the new generation, the use of ICT technologies provided for by the professional standard of a teacher, including the information skills of a teacher.
Practical significance The development of this lesson model is to develop a number of key competencies necessary for the integrity of the chemistry course being studied.
Website used “The Most Unusual Periodic Table of Chemical Elements D.I. Mendeleev" is an educational product developed by my students in 2013. The main pedagogical task of this resource is to create a user-friendly interactive model of the Periodic Table of Chemical Elements by D.I. Mendeleev.
This lesson uses a variety of forms and methods of work, the purpose of which is to develop students’ abilities to analyze, compare, observe, and draw conclusions. During the lesson, the teacher asks questions, possible answers to them are highlighted in italics in the text. The lesson material corresponds to the program and is organically connected with previous lessons.
The emotional coloring of the lesson is enhanced not only by the use of the interactive Periodic Table, but also by the use of a presentation with various illustrations made by the student, as well as a demonstration of his own versions of the project “My Periodic Table”, and the inclusion of a funny song by Tom Lehrer.
I have a modern chemistry classroom, which has a multimedia computer lab. In such a laboratory, there is a laptop on each desktop. This makes it possible to simplify the work in the lesson as much as possible for students, and for the teacher to track the progress of tasks in pairs at each workplace.
Evaluation of students' activities. The number of grades for the described lesson is minimal: only the student’s speech on the discovery of the Periodic Law and individual lesson participants who correctly answered the quiz questions and participated in the design of the table at the end of the lesson are evaluated.
It will be possible to check the effectiveness of the acquired knowledge in the next lesson, when students submit their homework - the project “My Periodic Table”. The main goal of creating the project: to show students How in fact, the discovery of the Periodic Law could have occurred (contrary to the prevailing opinion that Dmitry Ivanovich dreamed of the table), and the complexity of classifying objects could be felt.
Main criteria for evaluating tables may be like this:
- Relevance of the topic (“chemistry” of creating a table, i.e. classification chemical concepts or substances, biographies of scientists, laureate chemists Nobel Prize different years etc.). If a student cannot find objects for classification in the subject “Chemistry”, he can turn to other sources, i.e. classify and compare, for example, cities by population and various countries. At the same time, in a “period” there may be a country, and in a “group” cities are located according to the increase in population. Each “element” of the student’s table must have a name, a number indicating the population, and be indicated by a symbol. For example, in the table of cities the city of Rostov-on-Don is suggested. Its symbol may be Ro. If there are several cities starting with the same letter, then the next letter should be added to the capital letter. Let’s say there are two cities starting with the letter “r”: Rostov-on-Don and Rivne. Then there will be an option for Rostov-on-Don Ro, and for the city of Rivne - Rb.
- Registration of work. The work may have a handwritten version, typed in Word or Excel (works 2013). I do not limit the size of the table. But I prefer A4 format. In my file of tables there is, for example, an option consisting of two sheets of Whatman paper. The work must be colorful and sometimes contain pictures or photographs. Accuracy is encouraged.
- Originality of the work.
- The abstract for the work includes the following parameters: the title of the work, the validity of the principle of arrangement of the selected “elements”. The student can also give reasons for the color palette of their table.
- Presentation of work. Each student defends his project, for which I provide 1 lesson in the program (this does not in any way interfere with the presentation of the program material in chemistry, since at the end of the year the program provides up to 6 lessons devoted to repeating the course through the study of biographies of different scientists, stories about substances and phenomena).
I am not the only one who evaluates the periodic system of students. High school students are involved in discussing the work, as well as my graduates, who can provide practical assistance to eighth-graders in preparing their work.
Progress in assessing student work. The experts and I fill out special sheets in which we give marks according to the criteria specified above on a three-point scale: “5” - full compliance with the criterion; “3” - partial compliance with the criterion; “1” - complete non-compliance with the criterion. The scores are then summed up and regular grades are entered into the journal. A student may receive multiple grades for this activity. For each point of the criterion or just one - total. I do not give unsatisfactory grades. The ENTIRE class takes part in the work.
Proposed view creative work provides for preliminary preparation, so students are given the task of “creating their own system” in advance. In this case, I do not explain the principle of constructing the original system; the guys will have to figure out on their own how Dmitry Ivanovich arranged the elements known at that time, what principles he was guided by.
Evaluation of the 8th grade students’ project “My Periodic Table”
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Registration of work |
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Abstract to the work |
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final grade |
Basic concepts used in the lesson
- Atomic mass
- Substance
- Group (main and secondary subgroup)
- Metals/non-metals
- Oxides (characteristics of oxides)
- Period
- Periodicity
- Periodic law
- Atomic radius
- Properties of a chemical element
- System
- Table
- Physical meaning of the basic quantities of the Periodic Table
- Chemical element
The purpose of the lesson
Study the Periodic Law and the structure of the Periodic Table of Chemical Elements D.I. Mendeleev.
Lesson Objectives
- Educational:
- Chemical element database analysis;
- To teach to see the unity of nature and the general laws of its development.
- Form the concept of “periodicity”.
- Study the structure of the Periodic Table of Chemical Elements D.I. Mendeleev.
- Developmental: Create conditions for the development of key competencies in students: Informational (extracting primary information); Personal (self-control and self-esteem); Cognitive (the ability to structure knowledge, the ability to highlight the essential characteristics of objects); Communicative (productive group communication).
- Educational: to promote the development of the intellectual resources of the individual through independent work with additional literature, Internet technologies; nurturing positive motivation for learning and correct self-esteem; ability to communicate in a team, group, build dialogue.
Lesson type
A lesson in learning new material.
Technologies
ICT technology, elements of critical thinking technology, elements of technology based on emotional-imaginative perception.
Expected educational results
- Personal: developing students’ readiness for self-education based on motivation to learn; formation of readiness for a conscious choice of a further educational trajectory by drawing up a lesson plan; formation of communicative competence in communication and cooperation with classmates through pair work.
- Meta-subject: developing the ability to independently determine the goals of one’s learning and develop the motive of one’s cognitive activity through goal setting in the lesson; developing the ability to conduct dialogue.
- Subject: formation of initial systematic ideas about the Periodic Law and the Periodic System of Elements D.I. Mendeleev, the phenomenon of periodicity.
Forms of training
Individual work of students, work in pairs, frontal work of the teacher with the class.
Means of education
Dialogue, handouts, teacher assignment, experience of interaction with others.
Stages of work
- Organizing time.
- Goal setting and motivation.
- Activity planning.
- Updating knowledge.
- Generalization and systematization of knowledge.
- Reflection.
- Homework.
During the classes
1. Organizational moment
Mutual greeting between teacher and students.
: Personal: self-organization; communicative – listening skills.
2. Goal setting and motivation
Teacher's opening speech. Since ancient times, contemplating the world around and admiring nature, man wondered: what, what substance are the bodies around man, man himself, the Universe made of.
Students are invited to consider the following images: seasons of the year, cardiogram of the heart (you can use a model of the heart), diagram “Structure solar system"; Periodic table of chemical elements D.I. Mendeleev ( different types) and answer the question: “What unites all the presented images?” (Periodicity).
Setting a goal. What do you guys think, what question will we talk about today (students make assumptions that the lesson will be about D.I. Mendeleev’s Periodic Table of Chemical Elements)? The notebook contains a note about the topic of the lesson: “Structure of the Periodic Table.”
Tasks for students:
- Select examples that indicate periodicity in nature. ( The movement of cosmic bodies around the center of the Galaxy, the change of day and night).
Suggest similar root words and phrases for the word “periodicity” (period, periodicals). - Who is the “author” of the Periodic Law ( DI. Mendeleev)? Can you "create" the Periodic Table ( the answer to this question will be delayed, it is given to the guys as homework )?
- Bluff game "Do you believe that..."
- Can you be awarded an aluminum mug after graduating from school? ( This is currently not possible. But Dmitry Ivanovich Mendeleev was presented with an aluminum bowl for his discovery of the Periodic Law, because... At that time, the cost of aluminum exceeded the price of gold and platinum.)
- Discovery by D.I. Can Mendeleev's Periodic Law be considered a feat? (Dmitry Ivanovich Mendeleev predicted several elements, unknown at that time, ekaboron (scandium), ekaaluminum (gallium), ekasilicon (germanium), ekamanganese (technetium). Well, he predicted and predicted. What is the feat? (Here it is appropriate to invite children to fantasize about theme of the SCIENTIST's feat) The fact is that for the first discovered element gallium (L. Boisbaudran, France), the density, and therefore the mass of the element, was incorrectly determined, and D.I. Mendeleev indicated not only the scientist’s mistake, but also its cause - insufficient purification of the gallium sample. If Dmitry Ivanovich had made a mistake with the calculations, he himself would have suffered, because his name would have been tarnished forever).
Teacher. Guys, before studying a new topic, I would like to “draw” a portrait of a scientist with you. Determine what qualities a scientist must have (the following are students’ assumptions about some qualities of a scientist: intelligence, enthusiasm, perseverance, perseverance, ambition, determination, originality).
Developable universal learning activities: subject learning activities: the ability to analyze the proposed pictures, find similarities between them. Personal: establishing a connection between the purpose of an activity and its motive. Regulatory: self-regulation. Cognitive: independent identification and formulation of goals; proof of your point of view. Communication skills: the ability to listen and engage in dialogue.
3. Activity planning
February 8, 2014 marked the 180th anniversary of the birth of the great Russian scientist Dmitry Ivanovich Mendeleev. Now we will watch a fragment of a film about the great scientist (the following is a fragment of the video film “Russian Da Vinci” or the cartoon “Three Questions to Mendeleev”).
March 1, 1869. a young and at that time little-known Russian scientist sent out a modest printed leaflet to chemists around the world entitled “Experience of a system of elements based on their atomic weight and chemical similarity." Let's go back in time and learn a little about how the Periodic Law was discovered. What follows is the student’s story about different versions of the Periodic Table (5-7 min.) using a presentation .
Students make notes in notebooks: the formulation of the Periodic Law and the date of its discovery (on the local network the teacher showswebsite andsection of the websitePeriodic law).
Teacher. What do you guys think, did scientists immediately accept the Periodic Law? Did you believe in him? To get a little taste of that era, let's listen to an excerpt from a poem about the discovery of gallium.
What conclusions should be drawn from this passage (students assume that in order to believe in new law, irrefutable evidence is needed)?
There are many variations of the Periodic Table. Various objects are classified: flowers, rejected elements, food products etc. All these tables share certain principles of construction, i.e. structure.
Developed universal learning activities: regulatory - drawing up a plan and sequence of actions; cognitive – building a logical chain of reasoning; communicative – the ability to listen and engage in dialogue, to accurately express one’s thoughts.
4. Updating knowledge
A comparison criterion is applicable to all laws - the possibility of predicting something new, foreseeing the unknown. Today you have to “discover” the Periodic Table for yourself, i.e. be a little scientist. To do this you need to complete the task.
Exercise. On your desktop there is a laptop with Internet access, there are instructions (Appendix 1) for working with the website “The Most Unusual Periodic Table of Elements D.I. Mendeleev" . Analyze the site interface and draw conclusions; reflect the results in the instruction card (Appendix 1).
If you don’t have a mobile computer lab, you can prepare paper instruction cards. In this case, the teacher works with the site together with the students). The teacher can: 1) distribute the assignment to students over a local network; 2) leave the file on the desktop of each laptop in advance. Students can give an answer to the teacher using the Paint or Word program, because There is no other type of feedback between the main (teacher) laptop and the mobile classroom (student laptops).
The student worksheet does not contain answers. The work is done in pairs. It is appropriate to allocate 10 minutes to complete the task. Students who complete the assignment first can show it to everyone on the local network (allow student to show demo).
Developable universal learning activities: personal: understanding the reasons for the success of educational activities; regulatory: finding errors and correcting them independently or with the help of a classmate, showing perseverance; communicative: assessing the partner’s actions to complete a task, the ability to listen and engage in dialogue.
5. Generalization and systematization of knowledge
The teacher checks the students’ work and, together with them, formulates a definition of the phenomenon of periodicity.
Teacher. Does the structure of the Periodic Table posted on the site differ from the tabular form proposed by D.I. Mendeleev? If yes, then highlight similar ones and features both tables (After finding out common features follows a joint formulation of the phenomenon of periodicity).
Periodicity– natural repeatability of changes in phenomena and properties.
Developable universal learning activities: personal: understanding the reasons for the success of educational activities; regulatory: finding errors and correcting them independently or with the help of a classmate; communicative – the ability to listen and engage in dialogue.
6. Reflection
The development of science confirmed the words of Dmitry Ivanovich himself about the development of the law; students could prepare this phrase at home by guessing the rebus. Answer:“The future does not threaten the periodic law with destruction, but only superstructures and development are promised.” It is also appropriate here to test knowledge in class using the TsOR collection (testing knowledge of periods and groups).
The lesson concludes with a song by Tom Lehrer.
Developable universal learning activities: subject: testing your own knowledge on the proposed test; regulatory awareness of acquired knowledge and methods of activity to achieve success; communicative – participation in collective discussion.
7. Homework
- §5, complete written tasks after paragraph: 1,4,5;
- In the lesson we saw different versions of the Periodic Table. At home, I suggest you “create” your own Periodic Table. this work will be completed in project format. Title: “My periodic table.” Goal: learn to classify objects, analyze their properties, be able to explain the principle of constructing your system of elements/objects.
Self-analysis of the lesson
The lesson showed its effectiveness. Most of the homework tested to create your own system of elements fully complied with the assessment criteria set out in the abstract, i.e. students consciously created tabular versions of their system of selected elements/objects.
The “My Periodic Table” project, which started as an exclusively paper version, gradually acquired a digitized form. This is how presentations, tabular versions in Excel and, finally, the COR appeared - the site “The Most Unusual Periodic Table of Elements D.I. Mendeleev". Samples of students’ work are posted on my website, in the “For Students” section, and in the “My Students’ Work” subsection.
Criteria and indicators of lesson effectiveness: positive emotional background of the lesson; cooperation of students; students’ judgments regarding the level of their own answers and opportunities for further self-education.
Subject: Atoms of chemical elements
Lesson type: Generalizing.
Lesson type: Lesson - presentation
Lesson Objectives : Summarize students’ knowledge on the topic, check the degree of mastery of the material;
stimulate cognitive activity, develop interest in the subject, mental operations to systematize knowledge, the ability to quickly and clearly formulate your thoughts, reason logically, and apply your knowledge in practice.
Equipment: Periodic table of chemical elements by D.I. Mendeleev (wall table, handouts for students’ desks), slide diagrams, computer, slide projector, screen.
Explanatory note for the lesson.
Currently, teachers are brief notes to the topics or sections being studied. This work helps
comprehend a large amount of factual material;
highlight the main, essential points of the topic;
give basic definitions.
When summarizing a topic, it is necessary to comprehend a large number of questions.
How to organize a lesson so as not to spend a lot of time taking notes at the blackboard, so that the lesson is visual, accessible, and activates the attention of students.
For this purpose, I use computer presentations in lessons. Of course, a lot of time is spent on developing a presentation. The teacher needs to highlight the main aspects of the topic, questions and compactly arrange the material on the slides. Think through each step of the lesson - the teacher’s questions, assume the student’s answer, the appearance of individual symbols on the slide (before or after the student’s answer).
The advantage of developing presentation lessons is that separate slides can be used when studying each section.
DURING THE CLASSES.
I . Lesson topic.
The teacher begins the lesson with the words of J. V. Goethe (on the screen on the first slide)
Difficulties increase as you approach your goal. But let everyone make their way like the stars, calmly, slowly, but continuously striving towards their intended goal.
Introduces students to the purpose and objectives of the lesson.
Lesson objectives:
1. Reinforce the concepts:
relative atomic mass;
relative molecular weight;
2. Systematize, generalize, consolidate knowledge:
about the structure of PSHE;
about the structure of the atom;
about changing the properties of elements in a period and group;
about the types of chemical bonds;
3. Strengthen the skill:
determine the coordinates of the element in the PSHE;
draw up a diagram of the structure of an atom and an ion;
express the composition of an atom;
write down a diagram of the formation of connections with various types communications
Slide – 3. To consolidate knowledge about the structure of the periodic table of chemical elements.
Teacher: The whole world is big: heat and cold, Is there a simple rule,
The planets are spinning, the light of dawn - What will unite the whole world?
Everything that we see outside, the periodic table is built by
Bound by law inside. Nature is looking for an alphabet...
E. Efimovsky
Now we will remember what a large apartment building looks like, which was built by D.I. Mendeleev. Who lives in this house?
(The teacher asks questions. After the students answer, symbols corresponding to the correct answer appear on the slide.)
What is a period? Number of periods in PSHE.
What are the periods? Why are they called that?
What is a group? Number of groups in PSHE.
How is each group divided?
Each chemical symbol in PSHE is designated by its own chemical symbol. Why chemical symbols written in different colors?
What did D.I. Mendeleev take as the basis for systematizing chemical elements?
What is the ordinal number of an element?
Slide – 4. Strengthen the ability to determine the coordinates of an element.
Teacher: To find a tenant in a huge house you need to know his exact address .
Unfortunately, the address on the slide is incomplete. In 3 minutes, use the PSHE to determine the missing coordinates.
We carry out the work in rows: 1st row - first line, 2nd row - second line, 3rd row - third line.
After completing the task, students voice their answer and symbols appear on the screen. Students fill out the table completely.
Slide – 5. Reinforce the concepts of relative atomic and relative molecular mass; consolidate the ability to calculate the value of relative molecular mass.
Teacher: The resident of each apartment has a special sign. It was she who played a role in the distribution of apartments. What kind of sign is this? Indicate it for a tenant living in the 1st entrance on the 5th floor.
Student: sign - relative atomic mass (definition); tenant - silver;
A r (Ag) = 108 ( Slide symbols appear as the student responds)
Teacher: Residents of different apartments are very friendly. As a rule, neighbors often gather for corporate events and parties, and they try not to change the composition of the company. ( The formula of phosphoric acid is on the screen). What can you say about the composition of this group? What is their special feature?
Student: Explains the composition of phosphoric acid, defines relative molecular weight, explains how to calculate relative molecular weight molecular weight of this connection.
Slide – 6. Reinforce your knowledge of the structure of the atom.
Teacher: We will devote the next few slides to solving the problem - what is the internal structure of the residents.
What particles do they consist of? What coordinate in the PS affects their structure?
Student: Talks about the structure of the atom. ( To ensure that the answer is complete and matches the slide, the teacher offers the student an answer plan)
What is at the center of an atom?
How is the nucleus charged?
What particles revolve around the nucleus?
What particles are in the nucleus?
What is the nuclear charge?
How to determine the number of protons in the nucleus?
How to determine total electrons orbiting the nucleus?
What is the number of neutrons in the nucleus?
Slide – 7, 8 . Strengthen the ability to express the composition of an atom.
Teacher: On the screen, using various numbers and letters, a record is presented that reflects the composition of the atom of one of the residents. Decipher it.
Student: Explains the meaning of each number. Why are the numbers of protons and neutrons shown in parentheses?
Teacher: You already find your way around a big house very easily - PS. Please indicate the composition of the chlorine atom based on its location.
(2-3 minutes are given to work. Then a slide appears on which students can check their notes).
Teacher: Compare the compositions of atoms? Who are they for each other?
Student: Finds common and distinctive features. Defines isotopes.
Slide – 9 . Strengthen the ability to draw up and explain the structure of an atom.
Teacher: We continue to study the internal structure of the atom. The screen shows the coordinates of the unknown resident's residence. Write down its diagram internal structure. (2 minutes) (The student who completed the task first gives the answer. Students check the completion of the task by recording on the screen)
Teacher: Is the structure diagram related to the position coordinates in the PS? Please answer the following questions: What does the nuclear charge correspond to?
How to determine the number of energy levels?
What is the total number of electrons in energy levels?
How did you determine the number of electrons in the last level?
Students answer the questions and complete the diagram.
Teacher: There are a lot of electrons nearby
They definitely don't live
And already on a new layer
The electron ascends.
The number of electrons increases from level to level. How to calculate the largest number of electrons in a given level?
Slide – 10 . To consolidate knowledge about the connection between the structure of an atom and its position in the PSHE.
Teacher: You and I have come to the conclusion that the structure of each atom depends on its position in the PS.
Match the diagrams of the structure of an atom and the signs of chemical elements. You are given 3-5 minutes to complete the task.
Slide – 11. Changes in the properties of atoms of chemical elements in periods.
The screen shows diagrams of the structure of lithium, beryllium, and boron atoms. What do these chemical elements have in common? (located in the same period)
How do the metallic and non-metallic properties of atoms of chemical elements change during a period?
Slide – 12. Changing the properties of atoms of chemical elements in groups.
1. The screen shows diagrams of the structure of boron, aluminum, and thallium atoms. What
What do these chemical elements have in common? (located in the same group)
2. How do the metallic and non-metallic properties of chemical atoms change?
elements in a group?
Slide – 13. Formation of ions.
What does screen recording mean?
What is an ion?
What is a positive ion called?
What is a negative ion called?
Slide – 14. Schemes of the structure of atoms and ions.
Option I – write down the structure diagrams of a calcium atom and a calcium ion.
Option II – write down the structure diagrams of the phosphorus atom and phosphorus ion P 3-
What do the ion structure schemes have in common?
Give an example of an atom of a chemical element that has the same structure.
Slide – 15 . Types of chemical bonds.
What is a chemical bond?
What types of chemical bonds do you know?
Three elements are given. Arrange the elements in order of decreasing electronegativity.
What is electronegativity called?
What is a non-polar covalent bond?
Give the formulas of compounds with covalent nonpolar bonds formed by these elements.
What is a polar covalent bond?
Give the formulas of compounds with polar covalent bonds formed by these elements.
What is an ionic bond?
Give the formulas of compounds with ionic bonds formed by these elements.
What is a metallic bond?
Give the formulas of compounds with metallic bonds formed by these elements.
Slide – 16. Scheme of formation of a covalent nonpolar bond.
We consider the formation of a covalent nonpolar bond using the example of the formation of a fluorine molecule.
Comment on the image on the slide.
Slide – 17. Scheme of formation of a polar covalent bond.
We consider the formation of a polar covalent bond using the example of the formation of a hydrogen fluoride molecule.
Explain the mechanism of bond formation.
What do covalent nonpolar and covalent polar bonds have in common and how do they differ?
Slide – 17 . Scheme of ionic bond formation.
We consider the formation of a new bond using the example of the formation of sodium fluoride.
Slide – 17 . Scheme of metal bond formation.
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