Metal in the voltage series after H 2

Metal sulfate in max s.o.

+
+ +

Metal (others)

+
+ +

HNO 3 concentrated

Metal nitrate in max d.o.

Metal (others; Al, Cr, Fe, Co, Ni when heated)

Nitratemetal

la in max s.o.

+
+

Metal (the rest in the yard of stresses up to N 2)

NO/N 2 O/N 2 /NH 3 (NH 4 NO 3)

depending on conditions

+

Metal (the rest in the series of stresses after H 2)

Fig.2. INTERACTION OF ACIDS WITH METALS

SALT

Salts – These are complex substances that dissociate in solutions to form positively charged ions (cations - basic residues), with the exception of hydrogen ions, and negatively charged ions (anions - acidic residues), other than hydroxide ions.

2.5 Properties of acids, bases and salts from the point of view of the theory of electrolytic dissociation

Let us consider, in the light of the theory of electrolytic dissociation, the properties of substances that exhibit the properties of electrolytes in aqueous solutions.

Acids. Acids have the following general properties:

the ability to interact with bases to form salts;

the ability to interact with certain metals with the release of hydrogen;

the ability to change the colors of indicators, in particular, to cause litmus to turn red;

sour taste.

When any acid dissociates, hydrogen ions are formed. Therefore, we must explain all the properties that are common to aqueous solutions of acids by the presence of hydrated hydrogen ions. They cause litmus to turn red, give acids a sour taste, etc. With the elimination of hydrogen ions, for example during neutralization, the acidic properties also disappear. Therefore, the theory of electrolytic dissociation defines acids as electrolytes that dissociate in solutions to form hydrogen ions.

In strong acids, which completely dissociate, the properties of acids are manifested to a greater extent, in weak ones - to a lesser extent. The better the acid dissociates, i.e. the greater its dissociation constant, the stronger it is.

The values ​​of acid dissociation constants vary over a very wide range. In particular, the dissociation constant of hydrogen cyanide is much less than that of acetic acid. And although both of these acids are weak, acetic acid is still much stronger than hydrogen cyanide. The values ​​of the first and second dissociation constants of sulfuric acid show that in relation to the first stage of dissociation, H 2 SO 4 is a strong acid, and in relation to the second, it is weak. Acids whose dissociation constants lie in the range 10 -4 - 10 -2 are sometimes called acids of medium strength. These, in particular, include orthophosphoric and sulfurous acids (in relation to dissociation in the first step).

Grounds. Aqueous solutions of bases have the following general properties:

the ability to interact with acids to form salts;

the ability to change the colors of indicators differently than acids change them (for example, they cause litmus to turn blue);

A peculiar “soapy” taste.

Since all solutions of bases have in common the presence of hydroxide ions in them, it is clear that the carrier of the basic properties is the hydroxide ion. Therefore, from the point of view of the theory of electrolytic dissociation, bases are electrolytes that dissociate in solutions with the elimination of hydroxide ions.

The strength of bases, like the strength of acids, depends on the value of the dissociation constant. The greater the dissociation constant of a given base, the stronger it is.

There are hydroxides that can interact and form salts not only with acids, but also with bases. These hydroxides include zinc hydroxide. When it reacts, for example, with hydrochloric acid, zinc chloride is obtained:

Zn (OH) 2 + 2HCl = ZnСl 2 + 2H 2 O

and when interacting with sodium hydroxide - sodium zincate:

Zn (OH) 2 + 2NaOH = Na 2 ZnO 2 + 2H 2 O

Hydroxides having this property are called amphoteric hydroxides or amphoteric electrolytes. Such hydroxides, in addition to zinc hydroxide, include hydroxides of aluminum, chromium and some others.

The phenomenon of amphotericity is explained by the fact that in the molecules of amphoteric electrolytes, the bond strength between the metal and oxygen differs slightly from the bond strength between oxygen and hydrogen. Dissociation of such molecules is therefore possible at the sites of both of these bonds. If we denote an amphoteric electrolyte by the formula ROH, then its dissociation can be expressed by the diagram

H + + RO - - ROH-R + + OH -

Thus, in an amphoteric electrolyte solution there is a complex equilibrium in which dissociation products of both acid and base types participate.

The phenomenon of amphotericity is also observed among some organic compounds. It plays an important role in biological chemistry; for example, proteins are amphoteric electrolytes.

Salt. Salts can be defined as electrolytes that, when dissolved in water, dissociate, releasing positive ions other than hydrogen ions and negative ions other than hydroxide ions. There are no ions that are common to aqueous solutions of all salts; Therefore, salts do not have general properties. As a rule, salts dissociate well, and the lower the charges of the ions forming the salt, the better.

When acid salts are dissolved in a solution, metal cations, complex anions of the acidic residue, as well as ions that are products of the dissociation of this complex acidic residue, including H + ions, are formed. For example, when sodium bicarbonate is dissolved, dissociation proceeds according to the following equations:

NaHCO 3 = Na + + HCO 3 -

HCO 3 - = H + + CO 3 2-

When basic salts dissociate, acid anions and complex cations consisting of metal and hydroxyl groups are formed. These complex cations are also capable of dissociation. Therefore, OH - ions are present in the basic salt solution. For example, when hydroxomagnesium chloride is dissolved, dissociation proceeds according to the equations:

MgOHCl = MgOH + + Cl -

MgOH + = Mg 2+ + OH -

Thus, the theory of electrolytic dissociation explains the general properties of acids by the presence of hydrogen ions in their solutions, and the general properties of bases by the presence of hydroxide ions in their solutions. This explanation is not, however, general. There are known chemical reactions that occur with the participation of acids and bases, to which the theory of electrolytic dissociation is not applicable: In particular, acids and bases can react with each other without being dissociated into ions. Thus, anhydrous hydrogen chloride, consisting only of molecules, easily reacts with anhydrous bases. In addition, substances are known that do not contain hydroxo groups, but exhibit the properties of bases. For example, ammonia reacts with acids and forms salts (ammonium salts), although it does not contain OH groups. Thus, with hydrogen chloride it forms a typical salt - ammonium chloride:

NH 3 + HC1 = NH 4 C1

The study of reactions of this kind, as well as reactions occurring in non-aqueous media, led to the creation of more general ideas about acids and bases. One of the most important modern theories of acids and bases is the proton theory, put forward in 1923.

According to the proton theory, an acid is a proton donor, i.e. a particle (molecule or ion) that is capable of donating a hydrogen ion - a proton, and a base - a proton acceptor, i.e. a particle (molecule or ion) capable of accepting a proton. The relationship between acid and base is determined by the scheme:

Base + Proton - Acid

A base and an acid connected by this relationship are called conjugate. For example, the HSO 4 - ion is the conjugate base of the acid H 2 SO 4.

The reaction between an acid and a base is represented by the proton theory as follows:

(Acid) 1 + (Base) 2 = (Acid) 2 + (Base) 1

For example, in the reaction

HC1 + NH 3 = NH 3 + + Cl -

The Cl ion is the conjugate base of the acid HC1, and the NH 3 + ion is the conjugate acid of the NH 3 base.

The essential point in the proton theory is that a substance manifests itself as an acid or a base, depending on what other substance it reacts with. The most important factor in this case is the binding energy of the substance with the proton. Thus, in the series NH 3 - H 2 O - HF, this energy is maximum for NH 3 and minimum for HF. Therefore, when mixed with NH 3, water functions as an acid, and when mixed with HF, it functions as a base:

NH 3 + H 2 O = NH 4 + + OH -

HF + H 2 O = F - + H 3 O +

Buffer solutions

Buffer solutions

Buffer solutions

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Hydrolysis of salts. Features of soil hydrolysis

The hydrolysis reaction of a salt formed by a strong acid and a weak base can be schematically depicted as follows: M + + A - + H2O MOH + H + + A - , (16) and the hydrolysis constant Kg = . (17) The solution has an acidic reaction (СН+СН-)...

Hydrolysis of salts. Features of soil hydrolysis

The hydrolysis of salts formed by a weak acid and a weak base occurs especially deeply. Hydrolysis reaction: M+ + A - + H2O MOH + HA. (22) The hydrolysis products are still the same, although weakly, dissociated into ions...

Hydrolysis of salts. Features of soil hydrolysis

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Classes of inorganic substances. Electrolyte solutions. Atomic sizes and hydrogen bonding

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Grounds

Alkalis (sodium, potassium, lithium hydroxides) form hard, white, very hygroscopic crystals. The melting point is 322°C, KOH is 405°C, and 473°C. The crystal lattices of potassium hydroxide are cubic, like NaCl...

Grounds

From the previous subsection you can see that most hydroxides are insoluble in water under normal conditions. And only alkalis and hydroxides of the second group, the main subgroup, of the periodic system of chemical elements of D. I. Mendeleev...

The process of formation and growth of the germinal drop

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Electrolytes, their properties and applications

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DEFINITION

Reasons are called electrolytes, upon dissociation of which only OH - ions are formed from negative ions:

Fe(OH) 2 ↔ Fe 2+ + 2OH - ;

NH 3 + H 2 O ↔ NH 4 OH ↔ NH 4 + + OH - .

All inorganic bases are classified into water-soluble (alkalis) - NaOH, KOH and water-insoluble (Ba(OH) 2, Ca(OH) 2). Depending on the exhibited chemical properties, amphoteric hydroxides are distinguished among the bases.

Chemical properties of bases

When indicators act on solutions of inorganic bases, their color changes, so when a base gets into a solution, litmus becomes blue, methyl orange becomes yellow, and phenolphthalein becomes crimson.

Inorganic bases are able to react with acids to form salt and water, and water-insoluble bases react only with water-soluble acids:

Cu(OH) 2 ↓ + H 2 SO 4 = CuSO 4 +2H 2 O;

NaOH + HCl = NaCl + H 2 O.

Bases that are insoluble in water are thermally unstable, i.e. when heated, they undergo decomposition to form oxides:

2Fe(OH) 3 = Fe 2 O 3 + 3 H 2 O;

Mg(OH) 2 = MgO + H 2 O.

Alkalis (water-soluble bases) react with acidic oxides to form salts:

NaOH + CO 2 = NaHCO 3.

Alkalis are also capable of entering into interaction reactions (ORR) with some non-metals:

2NaOH + Si + H 2 O → Na 2 SiO 3 +H 2.

Some bases enter into exchange reactions with salts:

Ba(OH) 2 + Na 2 SO 4 = 2NaOH + BaSO 4 ↓.

Amphoteric hydroxides (bases) also exhibit the properties of weak acids and react with alkalis:

Al(OH) 3 + NaOH = Na.

Amphoteric bases include aluminum and zinc hydroxides. chromium (III), etc.

Physical properties of bases

Most bases are solids that vary in solubility in water. Alkalis are water-soluble bases that are most often white solids. Water-insoluble bases can have different colors, for example, iron (III) hydroxide is a brown solid, aluminum hydroxide is a white solid, and copper (II) hydroxide is a blue solid.

Getting grounds

Bases are prepared in different ways, for example, by the reaction:

- exchange

CuSO 4 + 2KOH → Cu(OH) 2 ↓ + K 2 SO 4 ;

K 2 CO 3 + Ba(OH) 2 → 2KOH + BaCO 3 ↓;

— interactions of active metals or their oxides with water

2Li + 2H 2 O→ 2LiOH +H 2;

BaO + H 2 O → Ba(OH) 2 ↓;

— electrolysis of aqueous salt solutions

2NaCl + 2H 2 O = 2NaOH + H 2 + Cl 2.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Modern chemical science represents many different branches, and each of them, in addition to its theoretical basis, has great applied and practical significance. Whatever you touch, everything around you is a chemical product. The main sections are inorganic and organic chemistry. Let's consider what main classes of substances are classified as inorganic and what properties they have.

Main categories of inorganic compounds

These include the following:

1. Oxides.
2. Salt.
3. Grounds.
4. Acids.

Each of the classes is represented by a wide variety of compounds of inorganic nature and is important in almost any structure of human economic and industrial activity. All the main properties characteristic of these compounds, their occurrence in nature and their production are studied in a school chemistry course without fail, in grades 8-11.

There is a general table of oxides, salts, bases, acids, which presents examples of each substance and their state of aggregation and occurrence in nature. Interactions that describe chemical properties are also shown. However, we will look at each of the classes separately and in more detail.

Group of compounds - oxides

4. Reactions as a result of which elements change CO

Me +n O + C = Me 0 + CO

1. Reagent water: formation of acids (SiO 2 exception)

CO + water = acid

2. Reactions with bases:

CO 2 + 2CsOH = Cs 2 CO 3 + H 2 O

3. Reactions with basic oxides: salt formation

P 2 O 5 + 3MnO = Mn 3 (PO 3) 2

4. OVR reactions:

CO 2 + 2Ca = C + 2CaO,

They exhibit dual properties and interact according to the principle of the acid-base method (with acids, alkalis, basic oxides, acid oxides). They do not interact with water.

1. With acids: formation of salts and water

AO + acid = salt + H 2 O

2. With bases (alkalis): formation of hydroxo complexes

Al 2 O 3 + LiOH + water = Li

3. Reactions with acid oxides: obtaining salts

FeO + SO 2 = FeSO 3

4. Reactions with OO: formation of salts, fusion

MnO + Rb 2 O = double salt Rb 2 MnO 2

5. Fusion reactions with alkalis and alkali metal carbonates: formation of salts

Al 2 O 3 + 2LiOH = 2LiAlO 2 + H 2 O

Each higher oxide, formed either by a metal or a non-metal, when dissolved in water, gives a strong acid or alkali.

Organic and inorganic acids

In classical sound (based on the positions of ED - electrolytic dissociation - acids are compounds that in an aqueous environment dissociate into cations H + and anions of acid residues An -. However, today acids have been carefully studied in anhydrous conditions, so there are many different theories for hydroxides.

Empirical formulas of oxides, bases, acids, salts consist only of symbols, elements and indices indicating their quantity in the substance. For example, inorganic acids are expressed by the formula H + acid residue n- . Organic substances have a different theoretical representation. In addition to the empirical one, you can write down a full and abbreviated structural formula for them, which will reflect not only the composition and quantity of the molecule, but also the order of the atoms, their connection with each other and the main functional group for carboxylic acids -COOH.

In inorganics, all acids are divided into two groups:

• oxygen-free - HBr, HCN, HCL and others;
• oxygen-containing (oxoacids) - HClO 3 and everything where there is oxygen.

Inorganic acids are also classified by stability (stable or stable - everything except carbonic and sulfurous, unstable or unstable - carbonic and sulfurous). In terms of strength, acids can be strong: sulfuric, hydrochloric, nitric, perchloric and others, as well as weak: hydrogen sulfide, hypochlorous and others.

Organic chemistry offers not the same variety. Acids that are organic in nature are classified as carboxylic acids. Their common feature is the presence of the -COOH functional group. For example, HCOOH (formic), CH 3 COOH (acetic), C 17 H 35 COOH (stearic) and others.

There are a number of acids that are especially carefully emphasized when considering this topic in a school chemistry course.

1. Solyanaya.
2. Nitrogen.
3. Orthophosphoric.
4. Hydrobromic.
5. Coal.
6. Hydrogen iodide.
7. Sulfuric.
8. Acetic or ethane.
9. Butane or oil.
10. Benzoin.

These 10 acids in chemistry are fundamental substances of the corresponding class both in the school course and in general in industry and syntheses.

Properties of inorganic acids

The main physical properties include, first of all, the different state of aggregation. After all, there are a number of acids that have the form of crystals or powders (boric, orthophosphoric) under normal conditions. The vast majority of known inorganic acids are different liquids. Boiling and melting points also vary.

Acids can cause severe burns, as they have the power to destroy organic tissue and skin. Indicators are used to detect acids:

• methyl orange (in normal environment - orange, in acids - red),
• litmus (in neutral - violet, in acids - red) or some others.

The most important chemical properties include the ability to interact with both simple and complex substances.

When interacting with metals, not all acids react equally. Chemistry (9th grade) at school involves a very shallow study of such reactions, however, even at this level the specific properties of concentrated nitric and sulfuric acid when interacting with metals are considered.

Hydroxides: alkalis, amphoteric and insoluble bases

Oxides, salts, bases, acids - all these classes of substances have a common chemical nature, explained by the structure of the crystal lattice, as well as the mutual influence of atoms in the molecules. However, if it was possible to give a very specific definition for oxides, then this is more difficult to do for acids and bases.

Just like acids, bases, according to the theory of ED, are substances that can decompose in an aqueous solution into metal cations Me n + and anions of hydroxyl groups OH - .

• Soluble or alkalis (strong bases that change Formed by metals of groups I and II. Example: KOH, NaOH, LiOH (that is, elements of only the main subgroups are taken into account);
• Slightly soluble or insoluble (medium strength, do not change the color of the indicators). Example: magnesium hydroxide, iron (II), (III) and others.
• Molecular (weak bases, in an aqueous environment they reversibly dissociate into ion molecules). Example: N 2 H 4, amines, ammonia.
• Amphoteric hydroxides (show dual basic-acid properties). Example: beryllium, zinc and so on.

Each group presented is studied in the school chemistry course in the “Fundamentals” section. Chemistry in grades 8-9 involves a detailed study of alkalis and poorly soluble compounds.

Main characteristic properties of bases

All alkalis and slightly soluble compounds are found in nature in a solid crystalline state. At the same time, their melting temperatures are usually low, and poorly soluble hydroxides decompose when heated. The color of the bases is different. If alkalis are white, then crystals of poorly soluble and molecular bases can be of very different colors. The solubility of most compounds of this class can be found in the table, which presents the formulas of oxides, bases, acids, salts, and shows their solubility.

Alkalies can change the color of indicators as follows: phenolphthalein - crimson, methyl orange - yellow. This is ensured by the free presence of hydroxo groups in the solution. That is why poorly soluble bases do not give such a reaction.

The chemical properties of each group of bases are different.

These are most of the chemical properties that bases exhibit. The chemistry of bases is quite simple and follows the general laws of all inorganic compounds.

Class of inorganic salts. Classification, physical properties

Based on the provisions of the ED, salts can be called inorganic compounds that dissociate in an aqueous solution into metal cations Me +n and anions of acidic residues An n-. This is how you can imagine salts. Chemistry gives more than one definition, but this is the most accurate.

Moreover, according to their chemical nature, all salts are divided into:

• Acidic (containing a hydrogen cation). Example: NaHSO 4.
• Basic (containing a hydroxo group). Example: MgOHNO 3, FeOHCL 2.
• Medium (consist only of a metal cation and an acid residue). Example: NaCL, CaSO 4.
• Double (include two different metal cations). Example: NaAl(SO 4) 3.
• Complex (hydroxo complexes, aqua complexes and others). Example: K 2.

The formulas of salts reflect their chemical nature, and also indicate the qualitative and quantitative composition of the molecule.

Oxides, salts, bases, acids have different solubility properties, which can be viewed in the corresponding table.

If we talk about the state of aggregation of salts, then we need to notice their uniformity. They exist only in solid, crystalline or powdery states. The color range is quite varied. Solutions of complex salts, as a rule, have bright, saturated colors.

Chemical interactions for the class of medium salts

They have similar chemical properties as bases, acids, and salts. Oxides, as we have already examined, are somewhat different from them in this factor.

In total, 4 main types of interactions can be distinguished for medium salts.

I. Interaction with acids (only strong from the point of view of ED) with the formation of another salt and a weak acid:

KCNS + HCL = KCL + HCNS

II. Reactions with soluble hydroxides producing salts and insoluble bases:

CuSO 4 + 2LiOH = 2LiSO 4 soluble salt + Cu(OH) 2 insoluble base

III. Reaction with another soluble salt to form an insoluble salt and a soluble one:

PbCL 2 + Na 2 S = PbS + 2NaCL

IV. Reactions with metals located in the EHRNM to the left of the one that forms the salt. In this case, the reacting metal should not interact with water under normal conditions:

Mg + 2AgCL = MgCL 2 + 2Ag

These are the main types of interactions that are characteristic of medium salts. The formulas of complex, basic, double and acidic salts speak for themselves about the specificity of the chemical properties exhibited.

The formulas of oxides, bases, acids, salts reflect the chemical essence of all representatives of these classes of inorganic compounds, and in addition, give an idea of ​​the name of the substance and its physical properties. Therefore, special attention should be paid to their writing. A huge variety of compounds is offered to us by the generally amazing science of chemistry. Oxides, bases, acids, salts - this is only part of the immense diversity.

The general properties of bases are determined by the presence of the OH - ion in their solutions, which creates an alkaline environment in the solution (phenolphthalein turns crimson, methyl orange turns yellow, litmus turns blue).

1. Chemical properties of alkalis:

1) interaction with acid oxides:

2KOH+CO 2 ®K 2 CO 3 +H 2 O;

2) reaction with acids (neutralization reaction):

2NaOH+ H 2 SO 4 ®Na 2 SO 4 +2H 2 O;

3) interaction with soluble salts (only if, when an alkali acts on a soluble salt, a precipitate forms or a gas is released):

2NaOH+ CuSO 4 ®Cu(OH) 2 ¯+Na 2 SO 4,

Ba(OH) 2 +Na 2 SO 4 ®BaSO 4 ¯+2NaOH, KOH(conc.)+NH 4 Cl(crystalline) ®NH 3 +KCl+H 2 O.

2. Chemical properties of insoluble bases:

1) interaction of bases with acids:

Fe(OH) 2 +H 2 SO 4 ®FeSO 4 +2H 2 O;

2) decomposition when heated. When heated, insoluble bases decompose into the basic oxide and water:

Cu(OH) 2 ®CuO+H 2 O

End of work -

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Atomic molecular studies in chemistry. Atom. Molecule. Chemical element. Mol. Simple complex substances. Examples

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All topics in this section:

Getting grounds
1. Preparation of alkalis: 1) interaction of alkali or alkaline earth metals or their oxides with water: Ca+2H2O®Ca(OH)2+H

Nomenclature of acids
The names of acids are derived from the element from which the acid is formed. At the same time, the names of oxygen-free acids usually have the ending -hydrogen: HCl - hydrochloric, HBr - hydrobromo

Chemical properties of acids
The general properties of acids in aqueous solutions are determined by the presence of H+ ions formed during the dissociation of acid molecules, thus, acids are proton donors: HxAn«xH+

Obtaining acids
1) interaction of acid oxides with water: SO3+H2O®H2SO4, P2O5+3H2O®2H3PO4;

Chemical properties of acid salts
1) acid salts contain hydrogen atoms that can take part in the neutralization reaction, so they can react with alkalis, turning into medium or other acid salts - with a smaller number

Obtaining acid salts
The acid salt can be obtained: 1) by the reaction of incomplete neutralization of a polybasic acid with a base: 2H2SO4+Cu(OH)2®Cu(HSO4)2+2H

Basic salts
Basic (hydroxo salts) are salts that are formed as a result of incomplete replacement of the hydroxide ions of the base with acid anions. Single acid bases, e.g. NaOH, KOH,

Chemical properties of basic salts
1) basic salts contain hydroxo groups that can take part in the neutralization reaction, so they can react with acids, turning into intermediate salts or basic salts with less

Preparation of basic salts
The main salt can be obtained: 1) by the reaction of incomplete neutralization of the base with an acid: 2Cu(OH)2+H2SO4®(CuOH)2SO4+2H2

Medium salts
Medium salts are the products of complete replacement of H+ ions of an acid with metal ions; they can also be considered as products of complete replacement of the OH ions of the base anion

Nomenclature of medium salts
In Russian nomenclature (used in technological practice) there is the following order of naming medium salts: the word is added to the root of the name of an oxygen-containing acid

Chemical properties of medium salts
1) Almost all salts are ionic compounds, therefore, in a melt and in an aqueous solution, they dissociate into ions (when current is passed through solutions or molten salts, the process of electrolysis occurs).

Preparation of medium salts
Most of the methods for obtaining salts are based on the interaction of substances of opposite nature - metals with non-metals, acidic oxides with basic ones, bases with acids (see Table 2).

Atomic structure
An atom is an electrically neutral particle consisting of a positively charged nucleus and negatively charged electrons. The atomic number of an element in the Periodic Table of Elements is equal to the charge of the nucleus

Composition of atomic nuclei
The nucleus consists of protons and neutrons. The number of protons is equal to the atomic number of the element. The number of neutrons in the nucleus is equal to the difference between the mass number of the isotope and

Electron
Electrons rotate around the nucleus in certain stationary orbits. Moving along its orbit, an electron does not emit or absorb electromagnetic energy. Emission or absorption of energy occurs

Rule for filling electronic levels and sublevels of elements
The number of electrons that can be at one energy level is determined by the formula 2n2, where n is the number of the level. Maximum filling of the first four energy levels: for the first

Ionization energy, electron affinity, electronegativity
Ionization energy of an atom. The energy required to remove an electron from an unexcited atom is called the first ionization energy (potential) I: E + I = E+ + e- Ionization energy

Covalent bond
In most cases, when a bond is formed, the electrons of the bonded atoms are shared. This type of chemical bond is called a covalent bond (the prefix "co-" in Latin

Sigma and pi connections
Sigma (σ)-, pi (π)-bonds - an approximate description of the types of covalent bonds in molecules of various compounds, the σ-bond is characterized by the fact that the density of the electron cloud is maximum

Formation of a covalent bond by the donor-acceptor mechanism
In addition to the homogeneous mechanism of covalent bond formation outlined in the previous section, there is a heterogeneous mechanism - the interaction of oppositely charged ions - the H+ proton and

Chemical bonding and molecular geometry. BI3, PI3
Figure 3.1 Addition of dipole elements in NH3 and NF3 molecules

Polar and non-polar bond
A covalent bond is formed as a result of the sharing of electrons (to form common electron pairs), which occurs during the overlap of electron clouds. In education

Ionic bond
An ionic bond is a chemical bond that occurs through the electrostatic interaction of oppositely charged ions. Thus, the process of education and

Oxidation state
Valency 1. Valency is the ability of atoms of chemical elements to form a certain number of chemical bonds. 2. Valency values ​​vary from I to VII (rarely VIII). Valens

Hydrogen bond
In addition to various heteropolar and homeopolar bonds, there is another special type of bond that has attracted increasing attention from chemists over the past two decades. This is the so-called hydrogen

Crystal lattices
So, the crystal structure is characterized by the correct (regular) arrangement of particles in strictly defined places in the crystal. When you mentally connect these points with lines, you get spaces.

Solutions
If crystals of table salt, sugar or potassium permanganate (potassium permanganate) are placed in a vessel with water, then we can observe how the amount of solid substance gradually decreases. At the same time, water

Electrolytic dissociation
Solutions of all substances can be divided into two groups: electrolytes conduct electric current, non-electrolytes do not conduct electricity. This division is conditional, because everything

Dissociation mechanism
Water molecules are dipole, i.e. one end of the molecule is negatively charged, the other is positively charged. The molecule has a negative pole approaching the sodium ion, and a positive pole approaching the chlorine ion; surround io

Ionic product of water
Hydrogen index (pH) is a value characterizing the activity or concentration of hydrogen ions in solutions. The hydrogen indicator is designated pH. The hydrogen index is numerically

Chemical reaction
A chemical reaction is the transformation of one substance into another. However, such a definition needs one significant addition. In a nuclear reactor or accelerator, some substances are also converted

Methods for arranging coefficients in OVR
Electronic balance method 1). We write the equation of the chemical reaction KI + KMnO4 → I2 + K2MnO4 2). Finding atoms

Hydrolysis
Hydrolysis is a process of exchange interaction between salt ions and water, leading to the formation of slightly dissociated substances and accompanied by a change in the reaction (pH) of the medium. The essence

Rate of chemical reactions
The reaction rate is determined by a change in the molar concentration of one of the reactants: V = ± ((C2 – C1) / (t2 - t

Factors affecting the rate of chemical reactions
1. The nature of the reacting substances. The nature of the chemical bonds and the structure of the reagent molecules play an important role. Reactions proceed in the direction of destruction of less strong bonds and the formation of substances with

Activation energy
The collision of chemical particles leads to a chemical interaction only if the colliding particles have energy exceeding some specific value. Let's consider each other

Catalysis catalyst
Many reactions can be accelerated or slowed down by the introduction of certain substances. The added substances do not participate in the reaction and are not consumed during its course, but have a significant effect on

Chemical equilibrium
Chemical reactions that proceed at comparable rates in both directions are called reversible. In such reactions, equilibrium mixtures of reagents and products are formed, the composition of which

Le Chatelier's principle
Le Chatelier's principle says that in order to shift the equilibrium to the right, you must firstly increase the pressure. Indeed, as the pressure increases, the system will “resist” the increase in con

Factors influencing the rate of a chemical reaction
Factors influencing the rate of a chemical reaction Increase the speed Reduce the speed Presence of chemically active reagents

Hess's law
Using table values

Thermal effect
During the reaction, bonds in the starting substances are broken and new bonds are formed in the reaction products. Since the formation of a bond occurs with the release, and its breaking occurs with the absorption of energy, then x