Cl 2 + 2KI \u003d I 2 + 2KCl

The molar mass of iodine, calculated using the table of chemical elements of D.I. Mendeleev, is equal to - 254 g / mol. Find the amount of substance formed iodine:

v(I 2) = m(I 2)/M(I 2)

At, opened in 1940
Electronic configurations of halogens: F - 1 s 2 2s 2 2p 5 ; Cl-1 s 2 2s 2 2p 6 3s 2 3p 5 ; Br-1 s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 5 ; I - 1 s 2 s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 2 5p 5 .

The orbital distribution of electrons in the outer electron layer is the same for all halogens

They have much in common in the structure of atoms and molecules. They are finishing building R-shells of the outer layer, so they all belong to the number of p-elements. The outer electron layer of halogen atoms lacks one electron to complete, therefore, the electronegativity of these elements is pronounced and in redox reactions they behave mainly as oxidizing agents.
Halogen molecules consist of two atoms (F2, Cl2, Br2, l2) interconnected by a covalent non-polar bond. Between the atoms in the halogen molecules there is one common electron pair. This indicates that in simple substances these elements are monovalent. The crystal lattice of halogens of the molecular type.
The atoms of different halogens differ in the number of electron layers, and therefore the radii of the halogen atoms are different (Table 11). As the charges of the nuclei increase, the radii of the atoms increase, which leads to a gradual decrease in the electronegativity from fluorine to iodine and a decrease in non-metallic properties. The most pronounced non-metal among the halogens is fluorine, the least bright is .

■ 1. How does the value of the atomic radius change depending on the increase in the charge of the atomic nucleus?
2. What type of halogen molecules?
3. What type of crystal lattice do halogens have?
4. What is the free state of halogens?
5. Why, when a halogen molecule is formed, only one electron pair appears between atoms?
6. How does the value of electronegativity change with increasing atomic radii?

Physical properties of halogens

All properties of halogens, both physical and chemical, depend on the structure of the atoms of the elements. These properties of various halogens are largely similar, but at the same time, each halogen has a number of features.
Fluorine- gas of light green color, characterized by extremely toxic properties. The boiling point of fluorine is -188°, the solidification point is -218°. Density 1.11 g/cm.
- yellow-green gas. It is also poisonous, has a sharp, suffocating, unpleasant odor. Chlorine is heavier than air, relatively well soluble in water (for 1 volume of water 2 volumes of chlorine), forming chlorine water; Cl2agi at a temperature of -34° turns into a liquid, and at -101° it solidifies. Density 1.568 g/cm3..
is the only liquid non-metal. This substance is red-brown in color, heavy, volatile. The vessel in which bromine is located is always colored by its pairs in a red-brown color.
Bromine has a heavy unpleasant odor (“bromine” translated into Russian means “malodorous”). It is poorly soluble in water, forming bromine water Br2aq. Bromine dissolves much better in organic solvents - benzene, toluene, chloroform.
If a small amount of benzene is added to bromine water and shaken well, after the separation of the liquids, you can see how the color of bromine water disappears, and the benzene that has collected at the top turns bright orange with dissolved bromine. This is due to the fact that benzene removed bromine from water due to its better solubility in benzene.
Bromine is stored in flasks with ground stoppers and ground caps. Rubber plugs for working with bromine, as well as for working with chlorine, are not applicable, since they quickly corrode. Bromine is much heavier than water (density 3.12 g/cm3). The boiling point of bromine is 63°, the solidification point is -7.3°.
- a crystalline substance, dark gray, in pairs - violet. The density of iodine is 4.93 g/cm3, melting point 113°, boiling point 184°. It is not possible to bring to melting, and even more so to boiling under normal conditions, since even with weak heating it immediately passes from a solid state into vapor - it sublimates. The transition from a solid state to a gaseous state, bypassing the liquid state, and vice versa is called sublimation. This property is characteristic not only for iodine, but also for some other substances. It is convenient to use for cleaning substances from impurities.
Iodine is poorly soluble in water. The color of iodine water I2aq is always light yellow. However, it is highly soluble in alcohol. This is used to prepare a 5-10% solution of iodine in alcohol, called iodine tincture. Iodine is also soluble in benzene, toluene, ether, carbon disulfide and other organic solvents. Interestingly, iodine dissolves very well in a solution of its own salts, for example, in potassium iodide. This solution, called Lugol's solution, is widely used in clinical laboratories.
If a little benzene is added to iodine water I2aq, when shaken, a colored benzene ring is also formed on the surface, but only crimson.

■ 7. How does the color intensity of halogens change with increasing nuclear charges?
8. What is the name of solutions of chlorine, bromine and iodine in water?
9. How does the density of halogens change with increasing nuclear charges?

10. Compile and fill in the table "Physical properties of halogens" according to the following model:
11. How to explain the low melting and boiling points of halogens from the point of view of the structure of the crystal lattice?
12. What is the relative density of fluorine and chlorine in air and hydrogen? If you do not know what the relative density of gases is, how it is determined and how to use it in calculations, refer to Appendix II, page 387. After that, you can answer the question.
13. What volume will take 20 kg of chlorine under normal conditions? If you have forgotten how to calculate the volume of gas under normal conditions, refer to.

Physiological action of halogens

All are poisonous in their physiological action. Fluorine is especially poisonous: when inhaled in small quantities, it causes pulmonary edema, in large quantities it causes destruction of lung tissue and death.
Chlorine- also a substance very poisonous, although to a somewhat lesser extent. During the First World War, it was used as a chemical warfare agent because it is heavier than air and holds well above the ground, especially in calm weather. The maximum allowable concentration of free chlorine in the air is 0.001 mg/l.
Chronic chlorine poisoning causes a change in complexion, pulmonary and bronchial diseases. In case of chlorine poisoning, a mixture of alcohol vapor with ether, as well as water vapor mixed with ammonia, should be used as an antidote, and it is imperative to first remove the victim to fresh air.
In small quantities, chlorine can cure diseases of the upper respiratory tract, as it has a detrimental effect on bacteria. Chlorine is used as a disinfectant to disinfect tap water.
Vapors of bromine cause suffocation. Poisonous and liquid bromine, causing severe burns when it comes into contact with the skin. It is recommended to pour bromine from one vessel to another with rubber gloves and under draft.
In case of contact with the skin, bromine should be washed off with an organic solvent - benzene or carbon tetrachloride, wiping the affected area with cotton wool moistened with these solvents. When bromine is washed off with water, it is often impossible to avoid a burn.

iodine the least toxic of all halogens. Inhalation of iodine vapor when it is heated can cause poisoning, but it is rare to work with vaporous iodine, for example, when cleaning it by sublimation. Crystalline iodine should not be taken by hand, as when it comes into contact with the skin, it causes the appearance of characteristic yellow spots. All work with halogens should be done in a fume hood.
However, halogens are vital elements. Chlorine in the form of table salt is constantly used in food, and is also part of green plants - chlorophyll. Lack of fluoride compounds in drinking water causes tooth decay. Iodine is essential for all living organisms, both plant and animal. It is involved in the regulation of metabolism. In the human body, iodine is concentrated mainly in the thyroid gland and is involved in the formation of its hormone. Lack of iodine causes painful changes in the thyroid gland. To prevent disease, iodine is added to food in very small quantities, diluting a few drops of iodine tincture in a glass of water, but more often in the form of sodium iodide and potassium iodide.

Write down safety precautions for working with halogens and first aid in case of poisoning in a notebook.

Chemical properties of halogens

By the nature of their chemical properties, as noted above, all halogens are typical non-metals with significant electronegativity. The most electronegative element with the highest non-metallic activity is fluorine, the least active is iodine.

Rice. 21. Combustion of hydrogen in chlorine. 1- chlorine 2-

Interaction of halogens with simple substances. You can trace the decrease in chemical activity from fluorine to chlorine using examples of various reactions. Of particular interest is the interaction of various halogens with hydrogen. Their reaction conditions are different.
Thus, fluorine reacts explosively with hydrogen even in the dark. In this case, fluoride is formed according to the equation.
H2+F2=2HF

Fluoride is the most durable compound among the hydrogen halides.
The interaction of chlorine with hydrogen occurs with an explosion only in the light:
Cl2 + H2 = 2HCl
If, however, a jet of hydrogen is ignited in an atmosphere of chlorine, then it will burn quietly with a colorless flame (Fig. 21).

With hydrogen, bromine forms hydrogen bromide.
Br2 + H2 = 2HBr
The process proceeds with low heat.
Iodine reacts with hydrogen only when heated to form hydrogen iodide:
H2 + I2 = 2HI
However, this compound is very unstable and easily decomposes to form hydrogen and iodine. In all these cases, the halogens behave as oxidizing agents. Hydrogen halides, when dissolved in water, form acids.

Halogens also show oxidizing properties when interacting with metals, which usually proceeds very actively.
Fluorine reacts with almost all metals. It is easy to trace the interaction of chlorine with metals. Many of them burn in chlorine, for example, they spontaneously ignite (Fig. 22). Others react with chlorine when heated, for example (Fig. 23).
2Na + Сl2 = 2NaCl
If they can have a different degree of oxidation, then when reacting with chlorine, they usually show the highest.

Rice. 22.

For example.
2Fe + 3Cl2 = 2FeCl3

Cu + Cl2 = CuCl2

Here, in reaction with chlorine, it exhibits an oxidation state equal to +3 - Fe +3, and equal to +2- Cu +2. In all the above cases, chlorine behaves like .

Chemistry of the Elements

Nonmetals of VIIA-subgroup

Elements of the VIIA-subgroup are typical non-metals with a high

electronegativity, they have a group name - "halogens".

Key Issues Addressed in the Lecture

General characteristics of non-metals of the VIIA-subgroup. Electronic structure, the most important characteristics of atoms. The most characteristic

oxidation foam. Features of the chemistry of halogens.

simple substances.

natural compounds.

Halogen compounds

Hydrohalic acids and their salts. Salt and hydrofluoric acid

slots, receiving and applying.

halide complexes.

Binary oxygen compounds of halogens. Instability ok-

The redox properties of simple substances and co-

unities. Disproportionation reactions. Latimer diagrams.

Chemistry of elements of the VIIA-subgroup

general characteristics

VIIA group is formed by p-elements: fluorine F, chlorine

Cl, bromine Br, iodine I and astatine At.

The general formula for valence electrons is ns 2 np 5.

All elements of group VIIA are typical non-metals.

to form a stable eight-electron

lochki, so they have a strong tendency towards

the addition of an electron.

All elements easily form simple singly charged

nye anions Г – .

In the form of simple anions, elements of group VIIA are found in natural water and in crystals of natural salts, for example, halite NaCl, sylvin KCl, fluorite

CaF2.

Common group name of elements VIIA-

groups "halogens", i.e. "giving birth to salts", due to the fact that most of their compounds with metals pre-

is a typical salt (CaF2, NaCl, MgBr2, KI), which

which can be obtained by direct mutual

interaction of a metal with a halogen. Free halogens are obtained from natural salts, so the name "halogens" is also translated as "born from salts."

The minimum oxidation state (–1) is the most stable

all halogens.

Some characteristics of the atoms of the elements of group VIIA are given in

The most important characteristics of atoms of elements of the VIIA group

Halogens have a high electron affinity (maximum for

Cl) and a very high ionization energy (maximum for F) and maximum

possible electronegativity in each of the periods. Fluorine is the most

electronegative of all chemical elements.

The presence of one unpaired electron in halogen atoms causes

leads to the union of atoms in simple substances into diatomic molecules Г2.

For simple halogen substances, oxidizing agents are most characteristic.

properties that are strongest for F2 and weaken on passing to I2.

Halogens are characterized by the greatest reactivity of all non-metallic elements. Fluorine, even among halogens, is isolated

is extremely active.

The element of the second period, fluorine, differs most strongly from the others.

some elements of the subgroup. This is a general pattern for all non-metals.

Fluorine, as the most electronegative element, does not show gender

living oxidation states. In any connections, including with Ki-

oxygen, fluorine is in the oxidation state (-1).

All other halogens exhibit positive oxidation states.

up to a maximum of +7.

The most characteristic oxidation states of halogens:

F: -1, 0;

Cl, Br, I: -1, 0, +1, +3, +5, +7.

Oxides are known for Cl, in which it is in the oxidation states: +4 and +6.

The most important halogen compounds, in positive

oxidation foams are oxygen-containing acids and their salts.

All halogen compounds in positive oxidation states are

are strong oxidizing agents.

terrible oxidation state. Disproportionation is promoted by an alkaline environment.

Practical application of simple substances and oxygen compounds

halogens is mainly due to their oxidizing effect.

Simple substances Cl2 find the widest practical application.

and F2. The largest amount of chlorine and fluorine is consumed in industrial or-

ganic synthesis: in the production of plastics, refrigerants, solvents,

pesticides, drugs. A significant amount of chlorine and iodine is used to obtain metals and for their refining. Chlorine is also used

for bleaching cellulose, for the disinfection of drinking water and in the production of

water of bleach and hydrochloric acid. Salts of oxo acids are used in the manufacture of explosives.

Acids are widely used in practice - hydrochloric and melting

Fluorine and chlorine are among the twenty most common elements

there, much less bromine and iodine in nature. All halogens are found in nature in the oxidation state(-one). Only iodine is found in the form of salt KIO3,

which, as an impurity, is included in the Chilean saltpeter (KNO3).

Astatine is an artificially obtained radioactive element (it does not exist in nature). The instability of At is reflected in the name, which comes from the Greek. "astatos" - "unstable". Astatine is a convenient emitter for radiotherapy of cancerous tumors.

Simple substances

Simple substances of halogens are formed by diatomic molecules G2.

In simple substances, during the transition from F2 to I2 with an increase in the number of electrons

electron layers and an increase in the polarizability of atoms, there is an increase

intermolecular interaction, leading to a change in the aggregate

standing under standard conditions.

Fluorine (under normal conditions) is a yellow gas, at -181 ° C it turns into

liquid state.

Chlorine is a yellow-green gas, it turns into a liquid at -34 ° C. With a color of ha-

the name Cl is associated with it, it comes from the Greek "chloros" - "yellow-

green". A sharp increase in the boiling point of Cl2 compared to F2,

indicates an increase in intermolecular interaction.

Bromine is a dark red, very volatile liquid, boils at 58.8 ° C. On-

the title of the element is associated with a sharp unpleasant smell of gas and is formed from

"bromos" - "stinking".

Iodine - dark purple crystals, with a slight "metallic" luster

skom, which, when heated, easily sublimes, forming violet vapors;

the boiling point of iodine is 183o C. Its name comes from the color of iodine vapor -

"iodos" - "violet".

All simple substances have a pungent odor and are poisonous.

Inhalation of their vapors causes irritation of the mucous membranes and respiratory organs, and at high concentrations - suffocation. During World War I, chlorine was used as a poison.

Gaseous fluorine and liquid bromine cause skin burns. Working with ha-

logens, precautions should be taken.

Since the simple substances of halogens are formed by non-polar molecules

cools, they dissolve well in non-polar organic solvents:

alcohol, benzene, carbon tetrachloride, etc. In water, chlorine, bromine and iodine are sparingly soluble, their aqueous solutions are called chlorine, bromine and iodine water. Br2 dissolves better than others, the concentration of bromine in sat-

brine solution reaches 0.2 mol/l, and chlorine - 0.1 mol/l.

Fluorine decomposes water:

2F2 + 2H2O = O2 + 4HF

Halogens exhibit high oxidative activity and transition

dyat into halide anions.

Г2 + 2e–  2Г–

Fluorine has a particularly high oxidative activity. Fluorine oxidizes noble metals (Au, Pt).

Pt + 3F2 = PtF6

It even interacts with some inert gases (krypton,

xenon and radon), for example,

Xe + 2F2 = XeF4

Many very stable compounds burn in an F2 atmosphere, for example,

water, quartz (SiO2).

SiO2 + 2F2 = SiF4 + O2

In reactions with fluorine, even such strong oxidizing agents as nitric and sulfur

acid, act as reducing agents, while fluorine oxidizes

included in their composition O(–2).

2HNO3 + 4F2 = 2NF3 + 2HF + 3O2 H2 SO4 + 4F2 = SF6 + 2HF + 2O2

The high reactivity of F2 creates difficulties with the choice of con-

structural materials for working with it. Usually, for these purposes,

They contain nickel and copper, which, when oxidized, form dense protective films of fluorides on their surface. The name F is associated with its aggressive action.

I mean, it comes from the Greek. "Ftoros" - "destroying".

In the series F2, Cl2, Br2, I2, the oxidizing ability weakens due to an increase in

changing the size of atoms and reducing electronegativity.

In aqueous solutions, the oxidizing and reducing properties of

substances are usually characterized using electrode potentials. The table shows the standard electrode potentials (Eo, V) for the half-reactions of the

formation of halogens. For comparison, the value of Eo for ki-

oxygen is the most common oxidizing agent.

Standard electrode potentials for simple substances halogens

Decreased oxidative activity

As can be seen from the table, F2 - the oxidizing agent is much stronger,

than O2, therefore F2 does not exist in aqueous solutions , it oxidizes water,

recovering to F–. Judging by the value of Eo, the oxidizing ability of Cl2

also higher than that of O2. Indeed, during long-term storage of chlorine water, it decomposes with the release of oxygen and with the formation of HCl. But the reaction is slow (the Cl2 molecule is noticeably stronger than the F2 molecule and

activation energy for reactions with chlorine is higher), dispro-

portioning:

Cl2 + H2 O  HCl + HOCl

In water, it does not reach the end (K = 3.9.10–4), therefore Cl2 exists in aqueous solutions. Br2 and I2 are even more stable in water.

Disproportionation is a very characteristic oxidative

reduction reaction for halogens. The disproportionation of the

poured in an alkaline environment.

Disproportionation of Cl2 in alkali leads to the formation of anions

Cl– and ClO– . The disproportionation constant is 7.5. 1015 .

Cl2 + 2NaOH = NaCl + NaClO + H2O

When iodine is disproportionated in alkali, I– and IO3 – are formed. Ana-

Br2 disproportionates iodine logically. The change in the product is disproportionate

The ionization is due to the fact that the anions GO– and GO2 – in Br and I are unstable.

The disproportionation reaction of chlorine is used in industrial

sti to obtain a strong and fast-acting hypochlorite oxidizing agent,

bleaching lime, bartholite salt.

3Cl2 + 6KOH = 5KCl + KClO3 + 3H2O

Interaction of halogens with metals

Halogens interact vigorously with many metals, for example:

Mg + Cl2 = MgCl2 Ti + 2I2  TiI4

Na + halides, in which the metal has a low oxidation state (+1, +2),

are salt-like compounds with a predominantly ionic bond. How to-

lo, ionic halides are solids with a high melting point

Metal halides, in which the metal has a high oxidation state

niya, are compounds with a predominantly covalent bond.

Many of them under normal conditions are gases, liquids or fusible solids. For example, WF6 is a gas, MoF6 is a liquid,

TiCl4 is a liquid.

Interaction of halogens with non-metals

Halogens interact directly with many non-metals:

hydrogen, phosphorus, sulfur, etc. For example:

H2 + Cl2 = 2HCl 2P + 3Br2 = 2PBr3 S + 3F2 = SF6

The bond in non-metal halides is predominantly covalent.

These compounds usually have low melting and boiling points.

In the transition from fluorine to iodine, the covalent character of the halides is enhanced.

Covalent halides of typical non-metals are acidic compounds; when interacting with water, they hydrolyze to form acids. For example:

PBr3 + 3H2O = 3HBr + H3PO3

PI3 + 3H2O = 3HI + H3PO3

PCl5 + 4H2O = 5HCl + H3PO4

The first two reactions are used to obtain bromine and hydrogen iodide

noic acid.

Interhalides. Halogens, combining with each other, form an inter-

leads. In these compounds, the lighter and more electronegative halogen is in the oxidation state (–1), and the heavier one is in the positive state.

oxidation foam.

Due to the direct interaction of halogens when heated, the following are obtained: ClF, BrF, BrCl, ICl. There are also more complex interhalides:

ClF3 , BrF3 , BrF5 , IF5 , IF7 , ICl3 .

All interhalides under normal conditions are liquid substances with low boiling points. Interhalides have a high oxidizing

activity. For example, such chemically stable substances as SiO2, Al2 O3, MgO, etc. burn in ClF3 vapors.

2Al2O3 + 4ClF3 = 4AlF3 + 3O2 + 2Cl2

Fluoride ClF 3 is an aggressive fluorinating reagent that acts quickly

yard F2 . It is used in organic syntheses and to obtain protective films on the surface of nickel equipment for working with fluorine.

In water, interhalides are hydrolyzed to form acids. For example,

ClF5 + 3H2O = HClO3 + 5HF

Halogens in nature. Obtaining simple substances

In industry, halogens are obtained from their natural compounds. All

processes for obtaining free halogens are based on the oxidation of halo-

nid ions.

2D –  Г2 + 2e–

A significant amount of halogens is found in natural waters in the form of anions: Cl–, F–, Br–, I–. Sea water can contain up to 2.5% NaCl.

Bromine and iodine are obtained from oil well water and sea water.

The structure and properties of atoms. The elements of the main subgroup of group VII of the Periodic system of D. I. Mendeleev, united under the general name halogens - fluorine F, chlorine Cl, bromine Br, iodine I, astatine At (rarely found in nature) are typical non-metals. This is understandable, because their atoms contain seven electrons in the outer energy level, and they lack only one electron to complete it. Halogen atoms, when interacting with metals, accept an electron from metal atoms. In this case, an ionic bond occurs and salts are formed.

Hence the common name of the subgroup "halogens", i.e. "giving birth to salts."

Halogens are very strong oxidizing agents. Fluorine in chemical reactions exhibits only oxidizing properties, and it is characterized only by the oxidation state -1 in compounds. The remaining halogens also exhibit reducing properties when interacting with more electronegative elements - fluorine, oxygen, nitrogen. Their oxidation states can take on the values ​​+1, +3, +5, +7.

The reducing properties of halogens increase from chlorine to iodine, which is associated with an increase in the radii of their atoms: chlorine atoms are about one and a half times smaller than iodine.

Halogens are simple substances. All halogens exist in the free state as diatomic molecules with a covalent non-polar chemical bond between the atoms. In the solid state, F 2 , Cl 2 , Br 2 , I 2 have molecular crystal lattices, which is confirmed by their physical properties (Table 7).

Table 7
Physical properties of halogens

As you can see, with an increase in the molecular weight of halogens, their melting and boiling points increase (Fig. 88), the density increases: fluorine and chlorine are gases, bromine is a liquid, iodine is a solid.

Rice. 88.
Melting and boiling points of halogens

This is due to the fact that with an increase in the size of atoms and molecules of halogens (Fig. 89), the forces of intermolecular interaction between them also increase.

Rice. 89.
Bond length in halogen molecules

From F 2 to I 2, the color intensity of the halogens increases. Iodine crystals have a metallic sheen.

The chemical activity of halogens, as non-metals, weakens from fluorine to iodine.

Each halogen is the strongest oxidizing agent in its period. The oxidizing properties of halogens are clearly manifested when they interact with metals. In this case, as you already know, salts are formed. Thus, fluorine already under normal conditions reacts with most metals, and when heated - with gold, silver, platinum, known for their chemical passivity. Aluminum and zinc ignite in a fluorine atmosphere:

The remaining halogens react with metals mainly when heated. So, in a flask filled with chlorine, crystals of crushed antimony flare up and burn beautifully (Fig. 90), while forming a mixture of two antimony chlorides (III) and (V):

Rice. 90.
Combustion of antimony in chlorine

Heated iron powder also ignites when interacting with chlorine. The experiment can also be carried out with antimony, but only iron filings must first be heated in an iron spoon, and then poured in small portions into a flask with chlorine. Since chlorine is a strong oxidizing agent, iron (III) chloride is formed as a result of the reaction (Fig. 91):

Rice. 91.
Burning iron in chlorine

Hot copper wire burns in bromine vapor:

Iodine oxidizes metals more slowly, but in the presence of water, which is a catalyst, the reaction of iodine with aluminum powder proceeds very rapidly:

The reaction is accompanied by the release of violet vapors of iodine (why?).

The decrease in the oxidizing and increase in the reducing properties of halogens from fluorine to iodine can also be judged by their ability to displace each other from salt solutions.

Rice. 92.
Displacement of bromine from its salt by a more active halogen - chlorine water

Free bromine displaces iodine from salts:

For fluorine, this reaction is not typical, since it occurs in solution, and fluorine interacts with water, displacing oxygen from it:

Here, oxygen plays an unusual role as a reducing agent. This is perhaps the only case when oxygen in the combustion reaction is not one of the initial substances, but its product.

The weakening of the oxidizing properties of halogens from fluorine to iodine is clearly manifested when they interact with hydrogen. The equation for this reaction can be written in general form:

H 2 + G 2 \u003d 2NG

(G - conventional chemical designation of halogens).

If fluorine interacts with hydrogen under any conditions with an explosion, then a mixture of chlorine with hydrogen reacts with an explosion only when ignited or irradiated with direct sunlight, bromine interacts with hydrogen when heated and without an explosion. These reactions are exothermic. The reaction of the compound of crystalline iodine with hydrogen is weakly endothermic; it proceeds slowly even when heated.

As a result of these reactions, hydrogen fluoride HF, hydrogen chloride HCl, hydrogen bromide HBr and hydrogen iodide HI are formed, respectively.

Discovery of halogens. Fluorine in free form was first obtained in 1886 by the French chemist A. Moissan, who was awarded the Nobel Prize for this. The element got its name from the Greek fluoros - "destroying".

Chlorine was discovered by the Swedish chemist K. Scheele in 1774. The element was named for the color of a simple substance (from the Greek chloros - yellow-green).

Bromine was discovered in 1826 by the French chemist A. Balard. The element is named so for the smell of a simple substance (from the Greek. Bromos - fetid).

Iodine was obtained in 1811 by the French scientist B. Courtois, and received the name for the color of the vapors of a simple substance (from the Greek iodes - violet).

New words and concepts

1. The structure of halogen atoms and their oxidation states.
2. Physical properties of halogens.
3. Chemical properties of halogens: interaction with metals, hydrogen, solutions of halogen salts.
4. Change in the redox properties of halogens from fluorine to iodine.

Tasks for independent work

1. Calculate the mass of 1 liter of fluorine and chlorine at n. y. Find their relative density in hydrogen and air.
2. Solutions of chlorine, bromine and iodine in water are respectively called chlorine, bromine and iodine water. Why is there no fluoride water?
3. Draw an analogy between the reactions of alkali metals and fluorine with salt solutions.
4. Calculate the oxidation states of atoms of chemical elements in the following compounds: KClO 3 (Bertolet salt), HClO (hypochlorous acid), HClO 4 (perchloric acid). Write the formulas of oxides corresponding to acids.
5. Calculate the volume of chlorine (n.a.) that will be required to displace all the iodine from 300 g of a 15% potassium iodide solution. Calculate the amount of new salt substance that is formed in this case.
6. Calculate the volume of hydrogen chloride that is formed when 150 liters of chlorine react with 200 liters of hydrogen. What gas is taken in excess? Calculate the volume that the excess of this gas will occupy.
7. In many countries, fluorine has a different name - fluorine, which means "fluid" in Latin. Find an explanation for this name using chemical dictionaries and other literature.

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