Soluble in water – alkalis are insoluble in water. Bases are complex compounds that, upon dissociation, form only hydroxide ions as anions. Only hydroxide ions as anions.

Quantum mechanical Bohr model of the N atom. Quantum numbers. The concept of an electron orbital.

There are currently two models of the atom: Bohr model(classical) and quantum mechanical. The first model is not suitable for describing atoms with a complex structure. The second model describes any atomic structure.

Electrons in an atom move in certain (stationary) electron orbits around the nucleus of the atom. Each such orbit for an electron is called an energy level. When an electron moves from one orbit to another, the electrons release or absorb energy.

The energy of an electron depends on the radius of its orbit. The electron that is in the orbit closest to the nucleus has the minimum energy. When an energy quantum is absorbed, the electron moves to an orbit with a higher energy (excited state). And vice versa, when moving from a high energy level to a lower one, an electron gives off (emits) a quantum of energy. An example of the structure of the hydrogen atom according to Bohr.

The concept of electron orbital and quantum numbers

E electron clouds are regions where an electron resides around the nucleus of an atom.

Electron orbital is the region of space around the nucleus of an atom with the highest probability of containing an electron (highest density - 90%).

The state of an electron in an atom is described using 4 numbers, which are called quantum numbers:

Principal quantum number n

Describes: the average distance from the orbital to the nucleus; the energy state of the electron in the atom.

The larger the value of n, the higher the energy of the electron and the larger the size of the electron cloud.

Acids, bases, salts in the light of TED. Step dissociation.

Using the theory of electrolytic dissociation, they define and describe the properties of acids, bases and salts.

Acids are electrolytes whose dissociation produces only hydrogen cations as cations.

For example:

HCl = H + + Cl - ; CH 3 COOH = H + + CH 3 COO -

The basicity of an acid is determined by the number of hydrogen cations that are formed during dissociation. So, HCl, HNO 3, - monobasic acids - one hydrogen cation is formed; H 2 S, H 2 SO 4 are dibasic, and H 3 PO 4 are tribasic, since two and three hydrogen cations are formed, respectively.

Dibasic and polybasic acids dissociate stepwise (gradually). For example:

H 3 PO 4 =H + +H 2 PO 4 - (first stage)

H 2 PO 4 - =H + +HPO 4 2- (second stage)

HPO 4 2- =H + +PO 4 3- (third stage)

Bases are electrolytes whose dissociation produces only hydroxyl ions as anions.

For example:

KOH=K + +OH - ;NH 4 OH=NH 4 + +OH -

Bases that are soluble in water are called alkalis. There are not many of them. These are the bases of alkali and alkaline earth metals:

LiOH, NaOH, KOH, RbOH, etc.

Most bases are slightly soluble in water.

The acidity of a base is determined by the number of its hydroxyl groups (hydroxy groups). For example, NH 4 OH is a one-acid base, Ca(OH) 2 is a two-acid base, Fe(OH) 3 is a three-acid base, etc. Two- and polyacid bases dissociate stepwise:

Ca(OH) 2 =Ca(OH) + +OH - (first stage)

Ca(OH) + =Ca 2+ +OH - (second stage)

Salts are electrolytes whose dissociation produces metal cations (as well as ammonium cations NH 4 +) and anions of acidic residues.

For example:

(NH 4) 2 SO 4 = 2NH 4 + + SO 4 2-; Na 3 PO4 = 3Na + + PO 4 3-

This is how medium salts dissociate. Acidic and basic salts dissociate stepwise.

KHSO 4 = K + + HSO 4 -

HSO 4 - = H + + SO 4 2-

Mg(OH)Cl = Mg(OH) + + Cl -

Mg(OH) + = Mg 2+ + OH -

Related information:

Gross domestic product (GDP) - similar to GNP, but includes only goods and services produced within national borders (including by foreign enterprises).

Reasons: classification, properties based on the concepts of the theory of electrolytic dissociation. Practical use.

Bases are complex substances that contain metal atoms (or an ammonium group NH 4) connected to one or more hydroxyl groups (OH).

In general, bases can be represented by the formula: Me(OH)n.

From the point of view of the theory of electrolytic dissociation(TED), bases are electrolytes whose dissociation produces only hydroxide anions (OH –) as anions. For example, NaOH = Na + + OH – .

Classification. BASES

Soluble in water – alkalis insoluble in water

For example, for example,

NaOH – sodium hydroxide Cu(OH) 2 – copper (II) hydroxide

Ca(OH) 2 – calcium hydroxide Fe(OH) 3 – iron (III) hydroxide

NH 4 OH – ammonium hydroxide

Physical properties. Almost all bases are solids. They are soluble in water (alkali) and insoluble. Copper (II) hydroxide Cu(OH) 2 is blue, iron (III) hydroxide Fe(OH) 3 is brown, most others are white. Alkali solutions feel soapy to the touch.

Chemical properties.

Soluble bases - alkalis	Insoluble bases (most of them)
1. Change the color of the indicator: red litmus - blue, colorless phenolphthalein - crimson.	---–– Indicators are not affected.
2. React with acids (neutralization reaction). Base + acid = salt + water 2KOH + H 2 SO 4 = K 2 SO 4 + 2H 2 O In ionic form: 2K + + 2OH – +2H + + SO 4 2– = 2K + + SO 4 2– + 2H 2 O 2H + + 2OH – = 2H 2 O	1. React with acids: Cu(OH) 2 + H 2 SO 4 = CuSO 4 + 2H 2 O Base + acid = salt + water.
3. React with salt solutions: alkali + salt = new. alkali + new salt (condition: formation of precipitate ↓or gas). Ba(OH) 2 + Na 2 SO 4 = BaSO 4 ↓ + 2 NaOH In ionic form: Ba 2+ + 2OH – + 2Na + + SO 4 2– = BaSO 4 ↓ + 2Na + +2OH – Ba 2+ + SO 4 2– = BaSO 4 .↓	2. When heated, they decompose into oxide and water. Cu(OH) 2 = CuO + H 2 O Reactions with salt solutions are not typical.
4. React with acid oxides: alkali + acid oxide = salt + water 2NaOH + CO 2 = Na 2 CO 3 + H 2 O In ionic form: 2Na + + 2OH – + CO 2 = 2Na + + CO 3 2– + H 2 O 2OH – + CO 2 = CO 3 2– + H 2 O	Reactions with acid oxides are not typical.
5. React with fats to form soap.	They do not react with fats.

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In the magical world of chemistry, any transformation is possible. For example, you can get a safe substance that is often used in everyday life from several dangerous ones. Such an interaction of elements, which results in a homogeneous system in which all reacting substances break down into molecules, atoms and ions, is called solubility. In order to understand the mechanism of interaction of substances, it is worth paying attention to solubility table.

In contact with

Classmates

A table showing the degree of solubility is one of the aids for studying chemistry. Those who are learning science may not always remember how certain substances dissolve, so you should always have a table handy.

It helps in solving chemical equations that involve ionic reactions. If the result is an insoluble substance, then the reaction is possible. There are several options:

The substance is highly soluble;
Slightly soluble;
Practically insoluble;
Insoluble;
Hydralizes and does not exist in contact with water;
Does not exist.

Electrolytes

These are solutions or alloys that conduct electric current. Their electrical conductivity is explained by the mobility of ions. Electrolytes can be divided into 2 groups:

Strong. They dissolve completely, regardless of the degree of concentration of the solution.
Weak. Dissociation is partial and depends on concentration. Decreases at high concentrations.

During dissolution, electrolytes dissociate into ions with different charges: positive and negative. When exposed to current, positive ions are directed towards the cathode, while negative ions are directed towards the anode. The cathode is a positive charge, the anode is a negative charge. As a result, ion movement occurs.

Simultaneously with dissociation, the opposite process takes place - the combination of ions into molecules. Acids are electrolytes whose decomposition produces a cation - a hydrogen ion. Bases - anions - are hydroxide ions. Alkalis are bases that dissolve in water. Electrolytes that are capable of forming both cations and anions are called amphoteric.

Ions

This is a particle in which there are more protons or electrons, it will be called an anion or cation, depending on what is more: protons or electrons. As independent particles, they are found in many states of aggregation: gases, liquids, crystals and plasma. The concept and name were introduced into use by Michael Faraday in 1834. He studied the effect of electricity on solutions of acids, alkalis and salts.

Simple ions carry a nucleus and electrons. The nucleus makes up almost all of the atomic mass and is made up of protons and neutrons. The number of protons coincides with the atomic number in the periodic table and the charge of the nucleus. The ion has no definite boundaries due to the wave motion of electrons, so it is impossible to measure their sizes.

Removing an electron from an atom requires, in turn, energy expenditure. It's called ionization energy. When an electron is added, energy is released.

Cations

These are particles that carry a positive charge. They can have different amounts of charge, for example: Ca2+ is a doubly charged cation, Na+ is a singly charged cation. They migrate to the negative cathode in an electric field.

Anions

These are elements that have a negative charge. It also has different amounts of charge, for example, CL- is a singly charged ion, SO42- is a doubly charged ion. Such elements are found in substances that have an ionic crystal lattice, in table salt and many organic compounds.

Sodium. Alkali metal. By giving up one electron located in the outer energy level, the atom will turn into a positive cation.
Chlorine. An atom of this element takes one electron to the last energy level, it will turn into a negative chloride anion.
Salt. The sodium atom gives an electron to chlorine, as a result of which in the crystal lattice the sodium cation is surrounded by six chlorine anions and vice versa. As a result of this reaction, a sodium cation and a chlorine anion are formed. Due to mutual attraction, sodium chloride is formed. A strong ionic bond is formed between them. Salts are crystalline compounds with ionic bonds.
Acid residue. It is a negatively charged ion found in a complex inorganic compound. It is found in acid and salt formulas and usually appears after the cation. Almost all such residues have their own acid, for example, SO4 - from sulfuric acid. Acids of some residues do not exist and are written formally, but they form salts: phosphite ion.

Chemistry is a science where it is possible to create almost any miracle.

The breakdown of electrolyte molecules into ions under the influence of polar solvent molecules is called electrolytic dissociation. Substances whose aqueous solutions or melts conduct electric current are called electrolytes.

These include water, acids, bases and salts. When dissolved in water, electrolyte molecules dissociate into positive ions - cations and negative - anions. The process of electrolytic dissociation is caused by the interaction of substances with water or another solvent, which leads to the formation of hydrated ions.

Thus, a hydrogen ion forms a hydronium ion:

H+ + H2O « H3O+.

To simplify, the hydronium ion is written without indicating water molecules, that is, H+.

NaCl + nH2O ® Na+(H2O)x + Cl–(H2O)n-x,

or the entry is accepted: NaCl « Na+ + Cl–.

Dissociation of acids, bases, salts

Acids are called electrolytes, upon dissociation of which only hydrogen cations are formed as cations. For example,

HNO3 « H+ + NO3–

Polybasic acids dissociate stepwise. For example, hydrogen sulfide acid dissociates stepwise:

H2S « H+ + HS– (first stage)

HS– « H+ + S2– (second stage)

The dissociation of polybasic acids occurs mainly in the first step. This is explained by the fact that the energy that must be expended to separate an ion from a neutral molecule is minimal and becomes greater with dissociation at each subsequent step.

Reasons are called electrolytes that dissociate in solution and form only hydroxide ions as anions. For example,

NaOH ® Na+ + OH–

Polyacid bases dissociate stepwise

Mg(OH)2 « MgOH+ + OH– (first stage)

MgOH+ « Mg2+ + OH– (second stage)

The stepwise dissociation of acids and bases explains the formation of acidic and basic salts.

There are electrolytes that dissociate as both basic and acidic. They're called amphoteric.

H+ + RO– « ROH « R+ + OH–

Amphotericity is explained by the small difference in the strength of the R–H and O–H bonds.

Amphoteric electrolytes include water, hydroxides of zinc, aluminum, chromium (III), tin (II, IV), lead (II, IV), etc.

The dissociation of an amphoteric hydroxide, for example Sn(OH)2, can be expressed by the equation:

2H+ + SnO22– « Sn(OH)2 « Sn2+ + 2OH–

2H2O ¯ basic properties

2H+ + 2–

acid properties

Salts are called electrolytes, which upon dissociation form metal cations, or complex cations, and anions of acid residues, or complex anions.

Medium salts, soluble in water, dissociate almost completely

Al2(SO4)3 « 2Al3+ + 2SO42–

(NH4)2CO3 « 2NH4+ + CO32–

Acid salts dissociate stepwise, for example:

NaHCO3 « Na+ + HCO3– (first stage)

The anions of acid salts subsequently dissociate slightly:

HCO3– « H+ + CO32– (second stage)

The dissociation of a basic salt can be expressed by the equation

CuOHCl « CuOH+ + Cl– (first stage)

CuOH+ « Cu+2 + OH– (second stage)

The cations of the main salts dissociate in the second stage to an insignificant extent.

Double salts are electrolytes that, when dissociated, form two types of metal cations. For example

KAl(SO4)2 « K+ + Al3+ + 2SO42–.

Complex salts are electrolytes, the dissociation of which produces two types of ions: simple and complex. For example:

Na2 « 2Na+ + 2–

A quantitative characteristic of electrolytic dissociation is degree of dissociationa, equal to the ratio of the number of molecules disintegrated into ions (n) to the total number of dissolved molecules (N)

The degree of dissociation is expressed in fractions of a unit or percentage.

According to the degree of dissociation, all electrolytes are divided into strong (a>30%), weak (a<3%) и средней силы (a - 3-30%).

Strong electrolytes When dissolved in water, they completely dissociate into ions. These include:

	HCl, HBr, HJ, HNO3, H2SO4, HClO3, HClO4, HMnO4, H2SeO4
Reasons	NaOH, KOH, LiOH, RbOH, CsOH, Ba(OH)2, Ca(OH)2, Sr(OH)2
	soluble in water (Appendix, Table 2)