Presentation on the topic periodic table of chemical elements. Presentation "The periodic law and the periodic system of chemical elements." Draw a diagram of the electronic structure for

1

Opening
periodic law
The basis of its classification
chemical elements D.I. Mendeleev
put two of their main and permanent
sign:
atomic mass value
properties formed by chemical
elements of substances.
2

Opening of Periodical
law
At the same time, he discovered that the properties
elements within certain limits
change linearly (monotonically
strengthen or weaken), then after
sharp jumps are repeated
periodically, i.e. after a certain
the number of elements found are similar.
3

First option
periodic table
Based on their
observations March 1, 1869 D.I.
Mendeleev formulated
periodic law, which
its initial
the wording sounded like this:
properties of simple bodies, and
also forms and properties
connections of elements
are in periodic
depending on the quantities
atomic weights of elements
4

Periodic law
DI. Mendeleev
If you write the rows one below the other like this,
so that under lithium there is sodium, and under
neon - argon, we get the following
arrangement of elements:
Li Be B C N O
Na Mg Al Si PS
F Ne
Cl Ar
With this arrangement in vertical
columns
elements that are similar in their
properties.
5

Periodic law D.I. Mendeleev

Modern interpretation of the Periodic
law:
Properties of chemical elements
and the compounds they form
are in periodic
depending on the amount of charge
their atomic nuclei.
6

R
19
30,974
PHOSPHORUS
7

8

Periods

Periods - horizontal rows
chemical elements, 7 periods in total.
Periods are divided into small (I, II, III) and
large (IV,V,VI), VII-unfinished.
9

Periods

Every period (except the first)
begins with a typical metal (Li, Na, K,
Rb, Cs, Fr) and ends with noble
gas (He, Ne, Ar, Kr, Xe, Rn), to which
preceded by a typical non-metal.
10

Groups

vertical columns
elements with the same
number of electrons per
external electronic
level equal to number
groups.
11

Groups

There are main (A) and
secondary subgroups (B).
The main subgroups consist
from elements small and large
periods.
Side subgroups consist
from elements only large
periods.
Such elements are called
transitional.
12

13

Remember!!!
Period number = number of energy
atomic levels.
Group number = number of outer electrons
atom.
(For elements of main subgroups)
14

Valence

The group number indicates the highest
valency of an element for oxygen.
15

Valence

Elements of groups IV, V, VI and VII form
volatile hydrogen compounds.
Group number shows
valency of the element in compounds with
hydrogen.
8-group no.
16

17

Exercise:

Name in what period and in
which group, subgroup
are the following
chemical elements:
Sodium, Copper, Carbon, Sulfur,
Chlorine, Chromium, Iron, Bromine
18

Changing the radius of an atom
in the period
The radius of an atom decreases with
an increase in the charges of atomic nuclei in a period.
19

Changing the radius of an atom
in the period
In one group with increase
period numbers atomic radii
are increasing.
20

Changes in atomic radii in the table D.I. Mendeleev

21

Exercise:

Compare the radii of the following
chemical elements:
Lithium, sodium, potassium
Boron, carbon, nitrogen
Oxygen, Sulfur, selenium
Iodine, Chlorine, fluorine
Chlorine, sulfur, phosphorus
22

Electronegativity
Electronegativity is
the ability of an atom to attract
electron density.
Electronegativity in period
increases with increasing
charge of the nucleus of a chemical element, then
is from left to right.
23

Electronegativity in
group increases with
decreasing number
electron layers of the atom
(down up).
The most
electronegative
the element is fluorine (F),
and the least
electronegative –
france (Fr).
24

RELATIVE ELECTRONEGATIVITY
ATOMS
N
2,1
Li
Be
WITH
N
ABOUT
0,98
1,5
IN
3,5
F
4,0
Na
Mg
Al
Si
P
S
Cl
0,93
1,2
TO
Ca
0,91
1,04
Rb
Sr
0,89
0,99
2,0
1,6
Ga
1,8
In
1,5
2,5
1,9
Ge
2,0
Sn
1,7
3,07
2,2
As
2,1
Sb
1,8
2,6
Se
2,5
Those
2,1
3,0
Br
2,8
I
2,6
25

Exercise:

Compare the EOs of the following
chemical elements:
Sodium and oxygen
Carbon and hydrogen
Oxygen and fluorine
Boron and nitrogen
Iodine, fluorine
Chlorine, phosphorus
26

properties
Reducing properties of atoms ability to lose electrons when

Oxidizing properties of atoms ability to accept electrons when
formation of a chemical bond.
27

Redox
properties
In the main subgroups from bottom to top, in
periods - from left to right
oxidative properties of simple
substances of elements increase, and
restorative properties,
respectively, decrease.
28

Changing Properties
chemical elements
Oxidizing and non-metallic
properties
Oxidizing and non-metallic properties
29

METALOIDS

B
Ge
Sb
Po
30

METALOIDS

According to its chemical properties
semimetals are nonmetals,
but according to the type of conductivity they belong to
conductors.
31

32

Thank you for your attention!!

33

ATOMIC STRUCTURE

34

ATOMIC STRUCTURE

1911 English scientist Ernest Rutherford
proposed a planetary model of the atom
35

Structure
atom
1. At the center of the atom is
positively charged
core.
2. All positive charge
and almost the entire mass of an atom
concentrated in its core.
Particle
3. The nuclei of atoms consist of
protons and neutrons
(nucleons).
4. Around the core along closed
orbits rotate
electrons.
Charge Mass
number
Electron
e–
-1
0
Proton
p+
+1
1
Neutron
n0
0
1
36

37

Atomic structure

electron
proton
neutron
38

A chemical element is a type
atoms with the same charge
kernels.
Ordinal
number
element
in PS
=
Charge
kernels
Number
Number
= protons = electrons
in the core
ē
Core charge
ordinal
number →
12
Mg
Number of protons
Number of electrons
Z = +12
р+ = 12
ē = 12
39

Number of neutrons

In the atoms of one chemical
element number
p+ protons are always the same
(equal to the charge of the nucleus Z), and the number
neutrons N varies.
40

Number of neutrons
Number
protons Z
+
Number
neutrons N
=
Mass
number A
Number of neutrons N = A -Z
Mass number -
24
serial number -
12
Mg
N = 24 – 12 = 12
41

Sample tasks

Determine for the proposed CE:
serial number
mass number
nuclear charge
number of protons
number of electrons
number of neutrons
42

Isotopes are atoms of an element that have one
and the same nuclear charge, but different masses.
e–
-
e
–
e–
-
-
p+
n
+n
R
+
R
Isotopes
hydrogen
n
Hydrogen
Deuterium
Tritium
1H
2D
3T
Number
protons (Z)
same
1
1
1
Number
neutrons N
miscellaneous
0
1
2
Mass
number A
miscellaneous
1
2
3
43

Isotopes of chlorine
35
17
Cl
75%
37
17
Cl
25%
Ar = 0.75 * 35 + 0.25 * 37 = 35.5

The electron shell is the totality of all
electrons in an atom,
surrounding the core.
45

Electronic shell

An electron in an atom is in a bound
state with the nucleus and has energy,
which determines the energy level
on which the electron is located.
46

Electronic shell

An electron cannot have such
energy to be between
energy levels.
Aluminum atom
carbon atom
Atom
hydrogen
47

Stationary and excited states of the atom

48

1
E1< E2 < E3
2
core
3
Energy levels n
(Electronic layers) – aggregate
electrons with similar values
energy
Number of energy levels in an atom
equal to the number of the period in which
The CE is located in the PSHE.
49

Define

Number
energy
levels for
H, Li, Na, K, Cu
50

Distribution of electrons by levels

N=2n2
formula
For
calculations
maximum number of electrons per
energy levels, where n is the level number.
1st level - 2 electrons.
2nd level - 8 electrons.
3rd level - 18 electrons.
51

Maximum number of electrons at level 1

Level 1: 2ē
52

Maximum amount
electrons at 1st and 2nd levels
Level 1: 2ē
Level 2:8ē
53

Maximum number of electrons at levels 1,2,3

1 level-2
Level 2-8
Level 3-18
54

Electronic structure diagram

Serial number
core charge +6, total number ē – 6,
Carbon 6C is in the second period
two energy levels (in the diagram
depicted in brackets, with a number written underneath them
electrons at a given energy level):
C +6))
6
2
4
55

Draw up an electronic structure diagram for:

Li,Na
Be, O, P,
F, Br
56

Energy levels
containing the maximum number
electrons are called
completed.
They have increased
sustainability and stability
Energy levels
containing a smaller number
electrons are called
unfinished
57

4
BERYLLIUM
2
2
9,0122
External energy level

Periodic Table of Chemical Elements

Number of energy
atomic levels.
= Period No.
Number of outer electrons = group no.
59

11
Na
22,99
sodium
60

Outer electrons

Number of outer electrons = group no.
Electron
external
level
61

Structure of energy levels

Each energy level
consists of sublevels: s, p, d, f.
A sublevel consists of orbitals.
Electron orbital - region
most likely
electron location in
space

Electron orbital

S-sublevel electrons moving around the nucleus
form a spherical electron cloud
Border
sublevels
S – cloud
63

Electrons of the p-sublevel form three
electronic clouds in the form of volumetric
eights
p – clouds
64

Shape of p-sublevel orbitals

65

Shape of d-sublevel orbitals

d - clouds
66

Shape of orbitals f – sublevel

67

p
-electron orbital,
-electrons,
-floor arrangement
denotes levels and sublevels
electrons.
The diagram shows
structure of 1st and 2nd
electronic levels
oxygen atom
68

Electronic graphic formulas
Electronic graphic
formulas
The sublevel consists of E orbitals
n=4 – 4 sublevels (S,р,d,f)
n=4
S
n=3
S
n=2
S
n=1 S
d
p
p
d
f
n=3 – 3 sublevels (S, р, d)
n=2 – 2 sublevels (S, р)
p
n=1 – 1 sublevel (S)
where n is the level number
69

Quantum numbers

The state of each electron in an atom
usually described using four
quantum numbers:
main (n),
orbital (l),
magnetic (m) and
spin (s).
The first three characterize the movement
electron in space, and the fourth around its own axis.
70

Quantum numbers

- energy parameters,
determining the state of the electron
and the type of atomic orbital in which
he is in.
1. Principal quantum number n
determines the total electron energy
and the degree of its removal from the nucleus
(energy level number);
n = 1, 2, 3, . . .
71

Quantum numbers

2. Orbital (side)
quantum number l determines the shape
atomic orbital.
Values ​​from 0 to n-1 (l = 0, 1, 2, 3,..., n-1).
Each value of l corresponds to
orbital of a special shape.
l = 0 - s-orbital,
l = 1 - p-orbital,
l = 2 - d-orbital,
l = 3 - f orbital
72

3. Magnetic quantum number m

- determines the orientation of the orbital in
space relative to the outside
magnetic or electric field.
m = 2 l +1
Values ​​range from +l to -l, including 0.
For example, when l = 1 the number m takes
3 values: +1, 0, -1, so there are
3 types of p-AO: px, py, pz.
73

Quantum numbers

4.Spin quantum number s can
take only two possible values
+1/2 and -1/2.
They correspond to two possible and
opposite directions
own magnetic moment
electron, called spin.


74

Properties of the electron
Spin characterizes one's own
magnetic moment of an electron.
To designate electrons with different
The symbols used for spins are: and ↓ .

Pauli's principle.
Hund's rule.
Principle of sustainability
Klechkovsky.
76

1) Pauli's exclusion
One joint stock company can have no more than two
electrons, which must have different
backs.
Allowed
Forbidden!
An atom cannot have two electrons with
the same set of all four
quantum numbers.
77

Planetary model of the berylium atom

4
BERYLLIUM
2
2
1s
9,0122
2s

Planetary model of the berylium atom

4
BERYLLIUM
2
2
1s
9,0122
2s
2p

Filling atomic orbitals with electrons

2) Hund's principle:
Steady state of an atom
corresponds to this distribution
electrons within
energy sublevel, at
which absolute value
total atomic spin
maximum
Allowed
Forbidden!
80

Rules for filling energy levels

Hund's rule
If, for example, in three
p-cells of the nitrogen atom need
distribute three electrons, then they
will be located each in
separate cell, i.e. be located
on three different
p-orbitals:
in this case the total spin
equals +3/2 since its projection
equal to
These same three electrons cannot
be located
Thus,
because then the projection
total spin
ms = +1/2-1/2+1/2=+1/2 .
ms = +1/2+1/2+1/2=+3/2 .
Forbidden!
Allowed
81

Filling atomic orbitals with electrons

3) Principle of sustainability
Klechkovsky.
JSCs are filled with electrons in
order of increasing energy
energy levels.
1s<2s<2p<3s<3p<4s<3d<4p<5s<4d
82

Klechkovsky's principle of stability.

First of all, those are filled in
orbitals whose min sum is (n+l).
For equal amounts (n+l), those with
of which n is less
1s< 2s < 2p < 3s < 3p < 4s < 3d ...
4s (4+0=4)
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d
83

ELECTRONIC FORMULA
ATOM
Using electronic formulas
(configurations) can be shown
distribution of electrons over
energy levels and sublevels:
1s<2s<2p<3s<3p<4s<3d<4p<5s<4d
1s2 2s22p6 3s23p6 3d0 4s2
84

ELECTRONIC FORMULA
Example: Carbon, No. 6, period II,
group IVA.
Electronic circuit
atomic structure
C+6))
2 4
Electronic formula: 1s2 2s22p2
85

Algorithm for composing electronic formulas.

We write down the sign of the chemical element and
charge of the nucleus of its atom (element number).
Determine the amount of energy
levels (period number) and number
electrons at each level.
We compose an electronic formula,
taking into account the level number, type of orbital and
number of electrons on it (principle
Klechkovsky).
86 structure of atoms
Li
Na
TO
Rb
O
S
Se
Those
90

91

conclusions

The structure of the external
energy levels
repeats periodically
therefore periodically
properties are repeated
chemical elements.
92

States of atoms
Atoms are stable only in certain areas
stationary states, which
correspond to certain energy values.
Lowest permitted energy
states of the atom are called ground, and all
the rest are excited.
Excited states of atoms are formed
from the ground state during the transition of one
or several electrons from occupied
orbitals into empty (or only occupied
93
1 electron)

Structure of the manganese atom:

Mn
+25
2
8
13
2
d - element
1s22s22p63s23p64s23d54p0
ground state of the atom
excited state of the atom
94

The importance of transition metals for the body and life.

Without transition metals our body
cannot exist.
Iron is the active principle
hemoglobin.
Zinc is involved in the production of insulin.
Cobalt is the center of vitamin B-12.
Copper, manganese and molybdenum, as well as
some other metals are included in
composition of enzymes.
95

Ions

Ion – positive or negative
charged particle formed by
donation or addition by an atom or
group of atoms of one or more
electrons
Cation – (+) charged particle, Kat
Anion – (-) charged particle, An
96

4. Comparison of metal
(non-metallic) properties with neighboring ones
period and subgroup elements.
5. Electronegativity, that is, force
attraction of electrons to the nucleus.
101

Thank you for your attention!

102

Internet resources used:

smoligra.ru
newpictures.club/s-p-d-f-orbitals
infourok.ru
Interesting videos
https://www.youtube.com/watch?v=3GbGjc-kSRw
103

Find correspondence between elements and their characteristics:

ELEMENT
SIGN
A. Lithium
B. Fluorine
B. Nitrogen
D. Beryllium.
1) s-element
2) Non-metal
3) number of protons 9
4) f-element
5) number of electrons 4
6) d-element
7) Metal
8) Highest EO by
compared to others
variants of atoms
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Prerequisites for the discovery of the Periodic Law

• Berzelius classification
• Döbereiner's triads
• Helix-axis of the Chancourtois screw
• Newlands Octaves
• Meyer tables

Dmitry Ivanovich Mendeleev was born on February 8, 1834 in Tobolsk, in the family of the director of the gymnasium, Ivan Pavlovich Mendeleev, and was the last, seventeenth child.

He was the closest adviser to the Chairman of the Cabinet of Ministers, Sergei Witte, who actually directed Russia along the path of state capitalism. And Mendeleev greatly contributed to this development.

Mendeleev was the ideologist of the oil industry in our country. His phrase “drowning with oil is like burning banknotes” became an aphorism. He understood the importance of petrochemicals and convinced Witte to build the first petrochemical plant in Russia

S. Witte

D. I. Mendeleev entered into a conflict with the Nobel brothers, which lasted throughout the 1880s. Ludwig Nobel, taking advantage of the crisis in the oil industry, and striving for a monopoly on Baku oil, on its production and distillation, for this purpose speculated on rumors about its depletion .

L. Nobel

Discovery of the Periodic Law by D.I. Mendeleev

• Classification of chemical elements according to characteristics: atomic mass and properties of substances formed by chemical elements.
• I wrote down on cards all the known information about the discovered and studied chemical elements and their compounds and compiled natural groups of elements with similar properties.
• Discovered that the properties of elements within certain limits change linearly (monotonically increase or decrease), then after a sharp jump repeat periodically , i.e. After a certain number of elements, similar ones occur.

First version of the periodic table

Based on his observations on March 1, 1869, D.I. Mendeleev formulated the periodic law, which in its initial formulation sounded like this: the properties of simple bodies, as well as the forms and properties of compounds of elements, are periodically dependent on the values ​​of the atomic weights of the elements

Periodic table

DI. Mendeleev

The weak point of the periodic law immediately after its discovery was the explanation of the reason for the periodic repetition of the properties of elements with an increase in the relative atomic mass of their atoms. Moreover, several pairs of elements are arranged in the Periodic Table with a violation of the increase in atomic mass. For example, argon with a relative atomic mass of 39.948 ranks 18th, and potassium with a relative atomic mass of 39.102 has an atomic number of 19.

Periodic law

DI. Mendeleev

Only with the discovery of the structure of the atomic nucleus and the establishment of the physical meaning of the atomic number of an element, it became clear that in the Periodic Table there are located in order of increasing positive charge of their atomic nuclei. From this point of view, there is no disturbance in the sequence of elements 18 Ar – 19 K, 27 Co – 28 Ni, 52 Te – 53 I, 90 Th – 91 Pa. Hence, modern interpretation of the Periodic Law sounds like this:

The properties of chemical elements and the compounds they form periodically depend on the charge of their atomic nuclei.

Periodic table

chemical elements

Periods are horizontal rows of chemical elements, 7 periods in total. The periods are divided into small (I, II, III) and large (IV, V, VI), VII - unfinished.

Each period (except for the first) begins with a typical metal (Li, Na, K, Rb, Cs, Fr) and ends with a noble gas (He, Ne, Ar, Kr, Xe, Rn), which is preceded by a typical non-metal.

Periodic table

chemical elements

Groups are vertical columns of elements with the same number of electrons in the outer electronic level, equal to the group number.

There are main (A) and secondary subgroups (B).

The main subgroups consist of elements of small and large periods. Side subgroups consist of elements of only large periods.

Redox

properties

Change in the radius of an atom in a period

The radius of an atom decreases with increasing charges of atomic nuclei in a period, because the attraction of the electron shells by the nucleus increases. At the beginning of the period there are elements with a small number of electrons in the outer electron layer and a large atomic radius. Electrons located further from the nucleus are easily separated from it, which is typical for metal elements

Changing the radius of an atom in a group

In the same group, as the period number increases, the atomic radii increase. Metal atoms give up electrons relatively easily and cannot gain them to complete their outer electron layer.

• In the Middle Ages, scientists already knew ten chemical elements - seven metals (gold, silver, copper, iron, tin, lead, and mercury) and three non-metal (sulfur, carbon, and antimony).

Designation of chemical elements by alchemists

Alchemists believed that chemical elements were associated with the stars and planets, and assigned astrological symbols to them.

Gold was called the Sun, and was designated by a circle with a dot:

Copper is Venus, the symbol of this metal was the “Venus mirror”:

And iron is Mars; As befits the god of war, the designation of this metal included a shield and a spear:

• Associated with the myths of the ancient Greeks - Tantalus and Promethium.

Promethium

In honor of the hero of the ancient myth Prometheus, who gave people fire and was doomed to terrible torment for this (an eagle flew to him, chained to a rock, and pecked at his liver), chemical element No. 61 promethium is named

Geographical origin

• Germanium Ge
• Galium Ga
• France Fr
• Ruthenium Ru
• Polonium Po
• Americium Am
• Europium Eu

In honor of scientists

• Curium Cm
• Fermium Fm
• Mendelevium Md
• Einstein Es
• Lawrence Lr

Names indicating the properties of simple substances

• Hydrogen (H) - giving birth to water
• Oxygen (O) – acid-producing
• Phosphorus (P) – carrier of light
• Fluorine (F) - destructive
• Bromine (Br) – smelly
• Iodine (I) - violet

• Mess in my head
• Not even a kick
• Bright head

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Slide captions:

Periodic table of chemical elements D.I. Mendeleev

MENDELEEV Dmitry Ivanovich (1834-1907) an outstanding Russian figure of science and culture, author of fundamental research in chemistry, chemical technology, physics, metrology, aeronautics, meteorology, agriculture, economics, etc.

History of the discovery of the table The discoverer of the table was the Russian scientist Dmitry Mendeleev. An extraordinary scientist with a broad scientific outlook managed to combine all ideas about the nature of chemical elements into a single coherent concept. By the middle of the 19th century, 63 chemical elements had been discovered, and scientists around the world have repeatedly made attempts to combine all existing elements into a single concept. It was proposed to place the elements in order of increasing atomic mass and divide them into groups according to similar chemical properties. In 1863, the chemist and musician John Alexander Newland proposed his theory, who proposed a layout of chemical elements similar to that discovered by Mendeleev, but the scientist’s work was not taken seriously by the scientific community due to the fact that the author was carried away by the search for harmony and the connection of music with chemistry. In 1869, Mendeleev published his diagram of the periodic table in the Journal of the Russian Chemical Society and sent notice of the discovery to the world's leading scientists. Subsequently, the chemist repeatedly refined and improved the scheme until it acquired its usual appearance. The essence of Mendeleev's discovery is that with increasing atomic mass, the chemical properties of elements change not monotonically, but periodically. After a certain number of elements with different properties, the properties begin to repeat. Thus, potassium is similar to sodium, fluorine is similar to chlorine, and gold is similar to silver and copper. In 1871, Mendeleev finally combined the ideas into the periodic law. The scientist predicted the discovery of several new chemical elements and described their chemical properties. Subsequently, the chemist’s calculations were completely confirmed - gallium, scandium and germanium fully corresponded to the properties that Mendeleev attributed to them.

The prototype of the scientific Periodic Table of Elements was the table “Experience of a system of elements based on their atomic weight and chemical similarity,” compiled by Mendeleev on March 1, 1869. Over the next two years, the author improved this table, introduced ideas about groups, series and periods of elements; made an attempt to estimate the capacity of small and large periods, containing, in his opinion, 7 and 17 elements, respectively. In 1870 he called his system natural, and in 1871 - periodic. Even then, the structure of the Periodic Table of Elements acquired largely its modern shape. The idea introduced by Mendeleev about the place of an element in the system turned out to be extremely important for the evolution of the Periodic Table of Elements; The position of the element is determined by the period and group numbers.

The periodic table of elements was developed by D. I. Mendeleev in 1869-1871.

The creation of the periodic system allowed D.I. Mendeleev to predict the existence of twelve elements unknown at that time: scandium (ekaboru), gallium (ekaaluminium), germanium (ekasilicon), technetium (ekamanganese), hafnium (an analogue of zirconium), polonium (ecatelur), astatine (ecaiodu), france (ecacesia), radium (ecabarium), sea anemone (ecalanthu), protactinium (ecatanthal). D.I. Mendeleev calculated the atomic weights of these elements and described the properties of scandium, gallium and germanium. Using only the position of the elements in the system, D.I. Mendeleev corrected the atomic weight of boron, uranium, titanium, cerium and indium.

Modern version of the periodic table of elements

A promising version of the element system

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The periodic table of chemical elements was discovered by the great Russian scientist Dmitri Mendeleev in March 1869 and finally formulated in the years.

MENDELEEV, Dmitry Ivanovich January 27 (February 8), 1834 - January 20 (February 2), 1907 Russian chemist Dmitry Ivanovich Mendeleev was born in Tobolsk in the family of a gymnasium director. Dmitry was the last, seventeenth child in the family. Of the seventeen children, eight died in infancy. While studying at the gymnasium, Mendeleev had very mediocre grades, especially in Latin.

In 1850, he entered the department of natural sciences of the physics and mathematics faculty of the Main Pedagogical Institute in St. Petersburg. In 1850, he entered the department of natural sciences of the physics and mathematics faculty of the Main Pedagogical Institute in St. Petersburg. In 1855, Mendeleev graduated from the institute with a gold medal and was appointed senior teacher at a gymnasium in Simferopol, but due to the outbreak of the Crimean War, he transferred to Odessa, where he worked as a teacher at the Richelieu Lyceum. In Mendeleev was on a scientific trip to Germany. In Mendeleev was on a scientific trip to Germany.

Upon his return, Mendeleev wrote Organic Chemistry, the first Russian textbook on this discipline, which was awarded the Demidov Prize. One of Mendeleev’s important discoveries dates back to this period - the determination of the “absolute boiling point of liquids,” now known as the critical temperature. He wrote the classic work "Fundamentals of Chemistry". In the preface to the second edition of the first part of the textbook, Mendeleev gave a table of elements entitled “Experience of a system of elements based on their atomic weight and chemical similarity”

In 1860, Mendeleev, together with other Russian chemists, took part in the International Congress of Chemists, at which S. Cannizzaro presented his interpretation of the molecular theory of A. Avogadro. This speech and discussion regarding the distinction between the concepts of atom, molecule and equivalent served as an important prerequisite for the discovery of the periodic law. In 1869, Mendeleev published his diagram of the periodic table in the Journal of the Russian Chemical Society and sent notice of the discovery to the world's leading scientists. Subsequently, the chemist repeatedly refined and improved the scheme until it acquired its usual appearance. The essence of Mendeleev's discovery is that with increasing atomic mass, the chemical properties of elements change not monotonically, but periodically.

One of the legends says that Mendeleev discovered the table of chemical elements in a dream. However, Mendeleev only laughed at the critics. “I’ve been thinking about it for maybe twenty years, and you say: I sat and suddenly... it’s done!” the scientist once said about his discovery.

Another legend credits Mendeleev with the discovery of vodka. In 1865, the great scientist defended his dissertation on the topic “Discourse on the combination of alcohol with water,” and this immediately gave rise to a new legend. The chemist’s contemporaries chuckled, saying that the scientist “creates quite well under the influence of alcohol combined with water,” and subsequent generations already called Mendeleev the discoverer of vodka.

Contemporaries also made fun of Mendeleev’s passion for suitcases. During the period of his involuntary inactivity in Simferopol, the scientist was forced to while away the time by weaving suitcases. Later, he independently made cardboard containers for the laboratory’s needs. Despite the clearly “amateur” nature of this hobby, Mendeleev was often called a “master of suitcases.”