Chemistry- the science of substances, the laws of their transformations (physical and chemical properties ah) and application.

Currently, more than 100 thousand inorganic and more than 4 million organic compounds are known.

Chemical phenomena: some substances turn into others that differ from the original in composition and properties, while the composition of the atomic nuclei does not change.

Physical phenomena: the physical state of substances changes (vaporization, melting, electrical conductivity, radiation of heat and light, malleability, etc.) or new substances are formed with a change in the composition of atomic nuclei.

Atomic - molecular science.

1. All substances are made up of molecules.

Molecule - the smallest particle of a substance that has its chemical properties.

2. Molecules are made up of atoms.

Atom - the smallest particle of a chemical element that retains all its chemical properties. Different atoms correspond to different atoms.

3. Molecules and atoms are in constant motion; there are forces of attraction and repulsion between them.

Chemical element - This is a type of atoms, characterized by certain nuclear charges and the structure of the electron shells. Currently, 118 elements are known: 89 of them are found in nature (on Earth), the rest are obtained artificially. Atoms exist in a free state, in compounds with atoms of the same or other elements, forming molecules. The ability of atoms to interact with other atoms and form chemical compounds determined by its structure. Atoms consist of a positively charged nucleus and negatively charged electrons moving around it, forming an electrically neutral system that obeys the laws characteristic of microsystems.

Atomic nucleus - the central part of the atom, consisting of Zprotons and N neutrons, in which the bulk of the atoms is concentrated.

Core charge - positive, equal in magnitude to the number of protons in the nucleus or electrons in a neutral atom and coincides with the ordinal number of the element in the periodic system.

The sum of protons and neutrons atomic nucleus called mass number A = Z + N.

Isotopes - chemical elements with the same nuclear charges, but different mass numbers due to the different number of neutrons in the nucleus.

Massive number ® Charge ® kernels

A Z

63 29

Cu and

65 29

35 17

Cl and

37 17

Chemical formula - this is a conditional record of the composition of a substance with the help of chemical signs (proposed in 1814 by J. Berzelius) and indices (the index is the number on the bottom right of the symbol. It indicates the number of atoms in a molecule). Chemical formula shows the atoms of which elements and in what ratio are connected to each other in the molecule.

Allotropy - the phenomenon of the formation of several simple substances by a chemical element, differing in structure and properties. Simple substances - molecules, consist of atoms of the same element.

Cfalse substances - molecules, consist of atoms of different chemical elements.

Atomic mass constant is equal to 1/12 of the mass of the isotope 12 C - the main isotope of natural carbon.

m u = 1/12 m (12 C ) = 1 amu = 1.66057 10 -24 g

Relative atomic mass (A r) is a dimensionless quantity equal to the ratio average weight atom of an element (taking into account percentage isotopes in nature) to 1/12 of the mass of an atom 12 C.

Average absolute mass of an atom (m) equal to the relative atomic mass multiplied by amu.

A r (Mg) = 24.312

m (Mg) = 24.312 1.66057 10 -24 = 4.037 10 -23 g

Relative molecular weight (M r) - a dimensionless value showing how many times the mass of a molecule of a given substance is greater than 1/12 of the mass of a carbon atom 12 C.

M g = m g / (1/12 m a (12 C))

m r - the mass of a molecule of a given substance;

m a (12 C) is the mass of a carbon atom 12 C.

M g = S A g (e). The relative molecular weight of a substance is equal to the sum of the relative atomic masses of all elements, taking into account the indices.

Examples.

M g (B 2 O 3) = 2 A r (B) + 3 A r (O) = 2 11 + 3 16 = 70

M g (KAl (SO 4) 2) = 1 A r (K) + 1 A r (Al) + 1 2 A r (S) + 2 4 A r (O) =
= 1 39 + 1 27 + 1 2 32 + 2 4 16 = 258

The absolute mass of the molecule equal to the relative molecular weight multiplied by amu. The number of atoms and molecules in ordinary samples of substances is very large, therefore, when characterizing the amount of a substance, a special unit of measurement is used - the mole.

Amount of substance, mol . It means a certain number of structural elements (molecules, atoms, ions). Denotedn , measured in mol. A mole is the amount of a substance containing as many particles as there are atoms in 12 g of carbon.

Avogadro's number (N A ). The number of particles in 1 mole of any substance is the same and is equal to 6.02 10 23. (Avogadro's constant has a dimension - mol -1).

Example.

How many molecules are there in 6.4 g of sulfur?

The molecular weight of sulfur is 32 g / mol. Determine the amount of g / mol of substance in 6.4 g of sulfur:

n (s) = m (s) / M (s ) = 6.4 g / 32 g / mol = 0.2 mol

Let us determine the number of structural units (molecules) using the constant Avogadro N A

N (s) = n (s)N A = 0.2 6.02 10 23 = 1.2 10 23

Molar mass shows the mass of 1 mole of a substance (denotedM).

M = m / n

The molar mass of a substance is equal to the ratio of the mass of a substance to the corresponding amount of a substance.

The molar mass of a substance is numerically equal to its relative molecular mass, however, the first value has the dimension g / mol, and the second is dimensionless.

M = N A m (1 molecule) = N A M g 1 amu = (N A 1 amu) M g = M g

This means that if the mass of a certain molecule is, for example, 80 amu. ( SO 3 ), then the mass of one mole of molecules is 80 g. Avogadro's constant is a coefficient of proportionality that ensures the transition from molecular to molar ratios. All statements regarding molecules remain valid for moles (when replacing, if necessary, amu by d) For example, the reaction equation: 2 Na + Cl 2 2 NaCl , means that two sodium atoms react with one chlorine molecule or, which is the same thing, two sodium moles react with one chlorine mole.

Classification chemical reactions in inorganic and organic chemistry carried out on the basis of various classifying features, information about which is given in the table below.

By changing the oxidation state of elements

The first sign of classification is based on a change in the oxidation state of the elements that form reagents and products.
a) redox
b) without changing the oxidation state
Redox are called reactions accompanied by a change in the oxidation states of chemical elements that make up the reagents. Redox in inorganic chemistry includes all substitution reactions and those decomposition reactions and compounds in which at least one simple substance is involved. All exchange reactions belong to the reactions proceeding without changing the oxidation states of the elements that form the reactants and reaction products.

By the number and composition of reagents and products

Chemical reactions are classified by the nature of the process, that is, by the number and composition of reagents and products.

Compound reactions chemical reactions are called, as a result of which complex molecules are obtained from several simpler ones, for example:
4Li + O 2 = 2Li 2 O

Decomposition reactions chemical reactions are called, as a result of which simple molecules are obtained from more complex ones, for example:
CaCO 3 = CaO + CO 2

Decomposition reactions can be viewed as the inverse of compound.

Substitution reactions chemical reactions are called, as a result of which an atom or group of atoms in a molecule of a substance is replaced by another atom or group of atoms, for example:
Fe + 2HCl = FeCl 2 + H 2 

Their distinguishing feature is the interaction of a simple substance with a complex one. Such reactions also exist in organic chemistry.
However, the concept of "substitution" in organic matter is broader than in inorganic chemistry. If in the molecule of the starting substance any atom or functional group is replaced by another atom or group, these are also substitution reactions, although from the point of view of inorganic chemistry, the process looks like an exchange reaction.
- exchange (including neutralization).
Exchange reactions are called chemical reactions that proceed without changing the oxidation states of the elements and lead to the exchange of the constituent parts of the reagents, for example:
AgNO 3 + KBr = AgBr + KNO 3

If possible, flow in the opposite direction

If possible, flow in the opposite direction - reversible and irreversible.

Reversible are called chemical reactions that occur at a given temperature simultaneously in two opposite directions with commensurate rates. When writing the equations of such reactions, the equal sign is replaced with oppositely directed arrows. The simplest example of a reversible reaction is the synthesis of ammonia by the interaction of nitrogen and hydrogen:

N 2 + 3H 2 ↔2NH 3

Irreversible are called reactions that proceed only in the forward direction, as a result of which products are formed that do not interact with each other. Irreversible include chemical reactions that result in the formation of low-dissociated compounds, the release of a large amount of energy, as well as those in which the final products leave the reaction sphere in a gaseous form or in the form of a precipitate, for example:

HCl + NaOH = NaCl + H2O

2Ca + O 2 = 2CaO

BaBr 2 + Na 2 SO 4 = BaSO 4 ↓ + 2NaBr

Thermal effect

Exothermic are called chemical reactions with the release of heat. Symbol changes in enthalpy (heat content) ΔH, and the heat effect of the reaction Q. For exothermic reactions, Q> 0, and ΔH< 0.

Endothermic are called chemical reactions that take place with heat absorption. For endothermic reactions Q< 0, а ΔH > 0.

Compound reactions will generally be exothermic and decomposition reactions will be endothermic. A rare exception is the reaction of nitrogen with oxygen - endothermic:
N2 + О2 → 2NO - Q

Phase

Homogeneous are called reactions that take place in a homogeneous medium (homogeneous substances, in one phase, for example, r-g, reactions in solutions).

Heterogeneous are called reactions that take place in an inhomogeneous medium, on the contact surface of reactants in different phases, for example, solid and gaseous, liquid and gaseous, in two immiscible liquids.

By using the catalyst

A catalyst is a substance that accelerates a chemical reaction.

Catalytic reactions proceed only in the presence of a catalyst (including enzymatic).

Non-catalytic reactions go in the absence of a catalyst.

By the type of disconnection

Homolytic and heterolytic reactions are distinguished by the type of breaking of a chemical bond in the parent molecule.

Homolytic are called reactions in which, as a result of the breaking of bonds, particles are formed that have an unpaired electron - free radicals.

Heterolytic called the reactions proceeding through the formation of ionic particles - cations and anions.

• homolytic (equal gap, each atom receives 1 electron)
• heterolytic (unequal break - one gets a pair of electrons)

Radical(chain) chemical reactions involving radicals are called, for example:

CH 4 + Cl 2 hv → CH 3 Cl + HCl

Ionic chemical reactions involving ions are called, for example:

KCl + AgNO 3 = KNO 3 + AgCl ↓

Heterolytic reactions of organic compounds with electrophiles - particles carrying a whole or fractional positive charge are called electrophilic. They are classified into electrophilic substitution and electrophilic addition reactions, for example:

C 6 H 6 + Cl 2 FeCl3 → C 6 H 5 Cl + HCl

H 2 C = CH 2 + Br 2 → BrCH 2 –CH 2 Br

Nucleophilic are heterolytic reactions of organic compounds with nucleophiles - particles that carry a whole or fractional negative charge. They are classified into nucleophilic substitution and nucleophilic addition reactions, for example:

CH 3 Br + NaOH → CH 3 OH + NaBr

CH 3 C (O) H + C 2 H 5 OH → CH 3 CH (OC 2 H 5) 2 + H 2 O

Classification of organic reactions

The classification of organic reactions is shown in the table:

Chemical reactions- these are processes as a result of which from some substances others are formed, differing from them in composition and (or) structure.

Classification of reactions:

I. By the number and composition of reactants and reaction products:

1) Reactions proceeding without changing the composition of the substance:

In inorganic chemistry, these are reactions of transformation of some allotropic modifications to others:

C (graphite) → C (diamond); P (white) → P (red).

In organic chemistry, these are isomerization reactions - reactions, as a result of which molecules of other substances of the same qualitative and quantitative composition are formed from the molecules of one substance, i.e. with the same molecular formula but with a different structure.

CH 2 -CH 2 -CH 3 → CH 3 -CH-CH 3

n-butane 2-methylpropane (isobutane)

2) Reactions proceeding with a change in the composition of a substance:

a) Compound reactions (in organic chemistry of addition) - reactions in the course of which one more complex is formed from two or more substances: S + O 2 → SO 2

In organic chemistry, these are the reactions of hydrogenation, halogenation, hydrohalogenation, hydration, and polymerization.

CH 2 = CH 2 + HOH → CH 3 - CH 2 OH

b) Decomposition reactions (in organic chemistry of elimination, elimination) - reactions in the course of which several new substances are formed from one complex substance:

CH 3 - CH 2 OH → CH 2 = CH 2 + H 2 O

2KNO 3 → 2KNO 2 + O 2

In organic chemistry, examples of cleavage reactions are dehydrogenation, dehydration, dehydrohalogenation, cracking.

c) Substitution reactions - reactions in which atoms of a simple substance replace the atoms of an element in a complex substance (in organic chemistry, reagents and reaction products are often two complex substances a).

CH 4 + Cl 2 → CH 3 Cl + HCl; 2Na + 2H 2 O → 2NaOH + H 2

Examples of substitution reactions not accompanied by a change in the oxidation states of atoms are extremely few. It should be noted the reaction of silicon oxide with salts of oxygen-containing acids, which correspond to gaseous or volatile oxides:

CaCO 3 + SiO 2 = CaSiO 3 + CO 2

Ca 3 (PO 4) 2 + 3SiO 2 = 3CaSiO 3 + P 2 O 5

d) Exchange reactions - reactions during which two complex substances exchange their constituent parts:

NaOH + HCl → NaCl + H 2 O,
2CH 3 COOH + CaCO 3 → (CH 3 COO) 2 Ca + CO 2 + H 2 O

II. By changing the oxidation states of chemical elements that form substances

1) Reactions proceeding with a change in oxidation states, or OVR:

∙ 2 | N +5 + 3e - → N +2 (reduction process, element is an oxidizing agent),

∙ 3 | Cu 0 - 2e - → Cu +2 (oxidation process, element - reducing agent),

8HNO 3 + 3Cu → 3Cu (NO 3) 2 + 2NO + 4H 2 O.

In organic chemistry:

C 2 H 4 + 2KMnO 4 + 2H 2 O → CH 2 OH – CH 2 OH + 2MnO 2 + 2KOH

2) Reactions proceeding without changing the oxidation states of chemical elements:

Li 2 O + H 2 O → 2LiOH,
HCOOH + CH 3 OH → HCOOCH 3 + H 2 O

III. Thermal effect

1) Exothermic reactions proceed with the release of energy:

C + O 2 → CO 2 + Q,
CH 4 + 2O 2 → CO 2 + 2H 2 O + Q

2) Endothermic reactions proceed with energy absorption:

СaCO 3 → CaO + CO 2 - Q

C 12 H 26 → C 6 H 14 + C 6 H 12 - Q

IV. By the state of aggregation of reactants

1) Heterogeneous reactions - reactions during which reactants and reaction products are in different states of aggregation:

Fe (tv) + CuSO 4 (rr) → Cu (tv) + FeSO 4 (rr),
CaC 2 (s) + 2H 2 O (l) → Ca (OH) 2 (solution) + C 2 H 2 (g)

2) Homogeneous reactions - reactions in which the reactants and reaction products are in one state of aggregation:

H 2 (g) + Cl 2 (g) → 2HCl (g),
2C 2 H 2 (g) + 5O 2 (g) → 4CO 2 (g) + 2H 2 O (g)

V. By catalyst participation

1) Non-catalytic reactions without the participation of a catalyst:

2H 2 + O 2 → 2H 2 O, C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

2) Catalytic reactions involving catalysts:

2H 2 O 2 → 2H 2 O + O 2

Vi. Towards

1) Irreversible reactions proceed in these conditions only in one direction:

C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

2) Reversible reactions under these conditions proceed simultaneously in two opposite directions: N 2 + 3H 2 ↔2NH 3

Vii. By the mechanism of flow

1) A radical mechanism.

A: B → A + B

A homolytic (equivalent) bond break occurs. In hemolytic rupture, a pair of electrons forming a bond is divided in such a way that each of the resulting particles receives one electron. In this case, radicals are formed - uncharged particles with unpaired electrons. Radicals are very reactive particles; reactions with their participation occur in the gas phase at high speed and often with an explosion.

Radical reactions occur between the radicals and molecules formed during the reaction:

2H 2 O 2 → 2H 2 O + O 2

CH 4 + Cl 2 → CH 3 Cl + HCl

Examples: combustion reactions of organic and inorganic substances, synthesis of water, ammonia, halogenation and nitration of alkanes, isomerization and aromatization of alkanes, catalytic oxidation of alkanes, polymerization of alkenes, vinyl chloride, etc.

2) Ionic mechanism.

A: B →: A - + B +

Heterolytic (unequal) bond cleavage occurs, while both bond electrons remain with one of the previously bonded particles. Charged particles (cations and anions) are formed.

Ionic reactions take place in solutions between the ions already present or formed during the reaction.

For example, in inorganic chemistry, this is the interaction of electrolytes in solution, in organic chemistry, these are addition reactions to alkenes, oxidation and dehydrogenation of alcohols, substitution of an alcohol group, and other reactions characterizing the properties of aldehydes and carboxylic acids.

VIII. By the type of energy that initiates the reaction:

1) Photochemical reactions occur when exposed to light quanta. For example, the synthesis of hydrogen chloride, the interaction of methane with chlorine, the production of ozone in nature, the processes of photosynthesis, etc.

2) Radiation reactions are initiated by high-energy radiation (X-rays, γ-rays).

3) Electrochemical reactions initiates electricity, for example, during electrolysis.

4) Thermochemical reactions are initiated by thermal energy. These include all endothermic reactions and many exothermic ones, which require heat to initiate.

Lecture: Classification of chemical reactions in inorganic and organic chemistry

Types of chemical reactions in inorganic chemistry

A) Classification by the amount of initial substances:

Decomposition - as a result of this reaction, from one existing complex substance, two or more simple, as well as complex substances are formed.

Example: 2H 2 O 2 → 2H 2 O + O 2

Compound - this is a reaction in which one, but more complex, is formed from two or more simple, as well as complex substances.

Example: 4Al + 3O 2 → 2Al 2 O 3

Substitution Is a certain chemical reaction that takes place between some simple, as well as complex substances. The atoms of a simple substance, in this reaction, are replaced by the atoms of one of the elements found in a complex substance.

Example: 2KI + Cl2 → 2KCl + I 2

Exchange Is a reaction in which two structurally complex substances exchange their parts.

Example: HCl + KNO 2 → KCl + HNO 2

B) Classification by thermal effect:

Exothermic reactions Are certain chemical reactions in which heat is released.
Examples:

S + O 2 → SO 2 + Q

2C 2 H 6 + 7O 2 → 4CO 2 + 6H 2 O + Q

Endothermic reactions Are certain chemical reactions in which heat is absorbed. As a rule, these are decomposition reactions.

Examples:

CaCO 3 → CaO + CO 2 - Q
2KClO 3 → 2KCl + 3O 2 - Q

Heat that is released or absorbed by a chemical reaction is called thermal effect.

The chemical equations in which the thermal effect of the reaction is indicated are called thermochemical.

C) Classification by reversibility:

Reversible reactions Are reactions that proceed under the same conditions in mutually opposite directions.

Example: 3H 2 + N 2 ⇌ 2NH 3

Irreversible reactions - these are reactions that proceed in only one direction, as well as complete consumption of all starting materials. With these reactions, you allocate gas, sediment, water.
Example: 2KClO 3 → 2KCl + 3O 2

D) Classification according to the change in the oxidation state:

Redox reactions - in the course of these reactions, a change in the oxidation state occurs.

Example: Cu + 4HNO 3 → Cu (NO 3) 2 + 2NO 2 + 2H 2 O.

Non-redox - reactions without changing the oxidation state.

Example: HNO 3 + KOH → KNO 3 + H 2 O.

E) Classification by phase:

Homogeneous reactions – reactions occurring in one phase, when the initial substances and reaction products have the same state of aggregation.

Example: H 2 (gas) + Cl 2 (gas) → 2HCL

Heterogeneous reactions - reactions occurring at the interface, in which the reaction products and the initial substances have a different state of aggregation.
Example: CuO + H 2 → Cu + H 2 O

Catalyst use classification:

A catalyst is a substance that speeds up the reaction. The catalytic reaction takes place in the presence of a catalyst, and the non-catalytic reaction takes place without a catalyst.
Example: 2H 2 0 2 MnO 2 → 2H 2 O + O 2 catalyst MnO 2

The interaction of alkali with acid takes place without a catalyst.
Example: KOH + HCl → КCl + H 2 O

Inhibitors are substances that slow down the reaction.
The catalysts and inhibitors themselves are not consumed during the reaction.

Types of chemical reactions in organic chemistry

Substitution Is a reaction during which one atom / group of atoms is replaced, in the original molecule, with other atoms / groups of atoms.
Example: CH 4 + Cl 2 → CH 3 Cl + HCl

Accession Are reactions in which several molecules of a substance combine into one. Addition reactions include:

• Hydrogenation is a reaction during which hydrogen is added at a multiple bond.

Example: CH 3 -CH = CH 2 (propene) + H 2 → CH 3 -CH 2 -CH 3 (propane)

Hydrohalogenation- a reaction that adds hydrogen halide.

Example: CH 2 = CH 2 (ethene) + HCl → CH 3 -CH 2 -Cl (chloroethane)

Alkines react with hydrogen halides (hydrogen chloride, hydrogen bromide) in the same way as alkenes. Joining in a chemical reaction takes place in 2 stages, and is determined by the Markovnikov rule:

When protic acids and water are attached to unsymmetrical alkenes and alkynes, a hydrogen atom is attached to the most hydrogenated carbon atom.

The mechanism of this chemical reaction. Formed in the 1st, fast stage, the p-complex in the 2nd slow stage gradually transforms into the s-complex - carbocation. In the 3rd stage, stabilization of the carbocation occurs - that is, interaction with the bromine anion:

I1, I2 - carbocations. P1, P2 - bromides.

Halogenation - the reaction in which halogen is added. Halogenation is also called all processes, as a result of which in organic compounds halogen atoms are introduced. This concept is used in a "broad sense". In accordance with this concept, the following chemical reactions based on halogenation are distinguished: fluorination, chlorination, bromination, iodination.

Halogenated organic derivatives are considered to be the most important compounds that are used both in organic synthesis and as target products. Halogenated hydrocarbons are considered to be feedstocks in a large number nucleophilic substitution reactions. As for the practical use of compounds containing halogen, they are used in the form of solvents, for example, chlorine-containing compounds, refrigerants - chlorofluorinated derivatives, freons, pesticides, pharmaceuticals, plasticizers, monomers for the production of plastics.

Hydration- reactions of addition of a water molecule to a multiple bond.

Polymerization - it special kind a reaction in which molecules of a substance having a relatively small molecular weight, attach to each other, subsequently forming molecules of a substance with a high molecular weight.

UDC 546 (075) BBK 24.1 i 7 0-75

Compiled by: Klimenko B.I Cand. tech. Sciences, Assoc. Volodchsnko AN, Cand. tech. Sciences, Assoc. Pavlenko V. I., Dr. Tech. Sciences, prof.

Reviewer Gikunova I.V., Cand. tech. Sciences, Assoc.

Fundamentals of Inorganic Chemistry: Guidelines for students of 0-75 days of study. - Belgorod: BelGTASM Publishing House, 2001 .-- 54 p.

V guidelines in detail, taking into account the main sections general chemistry, the properties of the most important classes of inorganic substances are considered. This work contains generalizations, diagrams, tables, examples, which will contribute to a better assimilation of the vast factual material. Special attention both in the theoretical and in the practical part, the connection of inorganic chemistry with the basic concepts of general chemistry is given.

The book is intended for first-year students of all specialties.

UDC 546 (075) BBK 24.1 i 7

© Belgorod State Technological Academy building materials(BelGTASM), 2001

INTRODUCTION

Knowledge of the foundations of any science and the problems it faces is the minimum that any person should know in order to freely navigate in the world around them. Natural science plays an important role in this process. Natural science is a set of natural sciences. All sciences are divided into exact (natural) and graceful (humanitarian). The first study the laws of development of the material world, the second - the laws of development and manifestations of the human mind. In this work, we will get acquainted with the basics of one of the natural sciences 7 inorganic chemistry. Successful study inorganic chemistry is possible only if the composition and properties of the main classes of inorganic compounds are known. Knowing the features of the classes of compounds, one can characterize the properties of their individual representatives.

When studying any science, including chemistry, the question always arises: where to start? From the study of factual material: descriptions of the properties of compounds, indicating the conditions of their existence, listing the reactions in which they enter; on this basis, the laws governing the behavior of substances are deduced, or, conversely, laws are first formulated, and then, on their basis, the properties of substances are discussed. In this book, we will use both techniques for presenting factual material.

1. BASIC CONCEPTS OF INORGANIC CHEMISTRY

What constitutes the subject of chemistry, what does this science study? There are several definitions of chemistry.

On the one hand, chemistry is the science of substances, their properties and transformations. On the other hand, chemistry is one of the natural sciences that studies the chemical form of motion of matter. The chemical form of motion of matter is the processes of the association of atoms into molecules and the dissociation of molecules. The chemical organization of matter can be represented by the following scheme (Fig. 1).

Rice. 1. Chemical organization of matter

Matter is an objective reality, given to man in his sensations, which is copied, photographed, displayed by our sensations, existing independently of us. Matter as an objective reality exists in two forms: in the form of matter and in the form of a field.

The field (gravitational, electromagnetic, intranuclear forces) is a form of existence of matter, which is characterized and manifested primarily by energy, not mass, although it possesses the latter. Energy is a quantitative measure of motion that expresses the ability of material objects to do work.

Mass (lat.massa - lump, lump, piece) - physical quantity, one of the main characteristics of matter, which determines its inertial and gravitational properties.

An atom is the lowest level of chemical organization of matter; an atom is the smallest particle of an element that retains its properties. It consists of a positively charged nucleus and negatively charged electrons; in general, the atom is electrically neutral. Chemical element - it is a kind of atoms with the same nuclear charge. There are 109 known elements, of which 90 exist in nature.

A molecule is the smallest particle of a substance that has the chemical properties of that substance.

The number of chemical elements is limited, and their combinations give everything

variety of substances.

What is substance?

In a broad sense, a substance is a specific type of matter that has a rest mass and is characterized under given conditions by certain physical and chemical properties. About 600 thousand inorganic substances and about 5 million organic substances are known.

In a narrower sense, a substance is a definite set of atomic and molecular particles, their associates and aggregates, which are in any of the three states of aggregation.

A substance is quite fully determined by three features: 1) it occupies a part of the space; 2) it has a rest mass;

3) built from elementary particles.

All substances can be divided into simple and complex.

cops form not one, but several simple substances. Such a phenomenon is called allotropy, and each of these simple substances is called allotropic modification (modification) of a given element. Allotropy is observed for carbon, oxygen, sulfur, phosphorus, and a number of other elements. Thus, graphite, diamond, carbyne, and fullerenes are allotropic modifications of the chemical element carbon; red, white, black phosphorus - allotropic modifications of the chemical element phosphorus. There are about 400 known simple substances.

A simple substance is a form of existence of chemical

elements in a free state

Simple substances are divided into metals and non-metals. The belonging of a chemical element to metals or non-metals can be determined using the periodic system of elements of D.I. Mendeleev. Before doing this, let's recall a little the structure of the periodic table.

1.1. Periodic law and periodic system of D.I. Mendeleev

Periodic table of elements - this is a graphic expression of the periodic law discovered by DI Mendeleev on February 18, 1869. The periodic law sounds like this: the properties of simple substances, as well as the properties of compounds, are periodically dependent on the charge of the nucleus of the element's atoms.

There are more than 400 options for displaying the periodic system. The most common cellular variants ( short version- 8-cell and long variants - 18- and 32-cell). The short period periodic system consists of 7 periods and 8 groups.

Elements with a similar structure of the external energy level are combined into groups. Distinguish between main (A) and secondary (B)

groups. The main groups are s- and p-elements, and the secondary -d- elements.

The period is a sequential row of elements, in the atoms of which the same number is filled electronic layers the same energy level. The difference in the sequence of filling the electronic layers explains the reason for the different lengths of the periods. In this regard, the periods contain different amount elements: 1st period - 2 elements; 2nd and 3rd periods - 8 elements each; 4th and 5th

periods - 18 elements each and the 6th period - 32 elements.

Elements of small periods (2nd and 3rd) are classified into a subgroup of typical elements. Since уd- and / elements are filled with the 2nd and 3rd outside the elgk-

the side of their atoms, and, consequently, a great ability to attach electrons (oxidizing ability), transferred high values their electronegativity. Elements with non-metallic properties occupy the upper right corner periodic system

D.I. Mendeleev. Non-metals can be gaseous (F2, O2, CI2), solid (B, C, Si, S) and liquid (Br2).

The element hydrogen occupies special place in periodic si

stem and has no chemical analogues. Hydrogen exhibits metallic

and non-metallic properties, and therefore in the periodic table its

placed simultaneously in the IA and VIIA group.

Due to the great originality of chemical properties, they are isolated from

efficiently noble gases(aerogens) - elements of group VIIIA
wild	systems. Research recent years allow nevertheless
her to rank some of them (Kr, Xe, Rn) as non-metals.
A characteristic property of metals is that the valence
thrones are loosely bound to a particular atom, and			inside everyone
there is a so-called electronic			Therefore all
possess	high electrical conductivity,	thermal conductivity

accuracy. Although there are brittle metals (zinc, antimony, bismuth). Metals, as a rule, exhibit reducing properties.

Complex substances(chemical compounds) are substances whose molecules are formed by atoms of various chemical elements (heteroatomic or heteronuclear molecules). For example, C 02, KON. More than 10 million complex substances are known.

Associates and aggregates are the highest form of the chemical organization of matter. Associates are combinations of simple molecules or ions into more complex substances that do not change the chemical nature. Associates exist mainly in a liquid and gaseous state, and aggregates in a solid state.

Mixtures are systems consisting of several evenly distributed compounds connected by constant ratios and not interacting with each other.

1.2. Valence and oxidation state

The compilation of empirical formulas and the formation of names of chemical compounds is based on knowledge and correct use concepts of oxidation state and valence.

Oxidation state- ego conditional charge of an element in a compound, calculated from the assumption that the compound consists of ions. This value is conditional, formal, since there are practically no purely ionic compounds. The absolute oxidation state can be an integer or fractional number; and in terms of charge it can be positive, negative and equal to zero.

Valence is a quantity determined by the number of unpaired electrons at the external energy level or by the number of free atomic orbitals capable of participating in the formation of chemical bonds.

Some rules for determining the oxidation states of chemical elements

1. The oxidation state of a chemical element in a simple substance

is equal to 0.

2. The sum of the oxidation states of atoms in a molecule (ion) is 0

(ion charge).

3. Elements of groups I-III A have a positive oxidation state corresponding to the number of the group in which this element is located.

4. Elements of IV -V IIА groups, except for the positive oxidation state corresponding to the group number; and the negative oxidation state corresponding to the difference between the group number and the number 8 have an intermediate oxidation state equal to the difference between the group number and the number 2 (Table 1).

Table 1

Oxidation states of elements IV -V IIА subgroups

			Oxidation state
			Intermediate

5. The oxidation state of hydrogen is +1 if the compound contains at least one non-metal; - 1 in compounds with metals (hydrides); 0 in H2.

Hydrides of some elements

	VeH2
NaH MgH2 ASh3
	CaH2	GaH3	GeH4	AsH3
	SrH2	InH3	SnH4	SbH3
	BaH2
Compounds H			Intermediate		Connections i t
			connections

6. The oxidation state of oxygen is usually -2, with the exception of peroxides (-1), superoxides (-1/2), ozonides (-1/3), ozone (+4), and oxygen fluoride (+2).

7. The oxidation state of fluorine in all compounds, except for F2> is equal to -1. In compounds with fluorine, higher forms of oxidation of many chemical elements (BiF5, SF6, IFα, OsFg) are realized.

eight . In periods, the orbital radii of atoms decrease with increasing sequence number, and the ionization energy increases. At the same time, acidic and oxidizing properties are enhanced; higher ste

oxidation foams of elements become less stable.

9. Elements of odd groups of the periodic table are characterized by odd, and elements of even groups are characterized by even degrees

oxidation.

10. In the main subgroups with increasing serial number element, the size of atoms generally increases, and the ionization energy decreases. Correspondingly, the basic properties are enhanced and the oxidizing properties weakened. In the subgroups of ^ -elements with an increase in the serial number, the participation of n. ^ - electrons in the formation of bonds

decreases, and therefore decreases					absolute value of step
no oxidation (Table 2).
							table 2
Values ​​of oxidation states of VA subgroup elements
				Oxidation state
Li, K, Fe, Ba	Acidic С 02, S 0 3
Nonmetals
	Amphoterized ZnO BeO
Amphigens	Double Fe304
Be, AL Zn
	yol-forming
Aerogens	CO, NO, SiO, N20
Ba (OH) 2 bases
Acids HNO3		HYDROXIDES
Ampholytes Zti (OH) 2
Average KagCO3,
Sour Manchuse,
Basic (SION) gCO3, 4 --------
Double CaMg (COs) 2
Mixed SaSGSU

> w h o w J 3 w "

Rice, 2. Scheme of the most important classes of inorganic substances