What are halogens? Chemical elements fluorine, chlorine, iodine and astatine. Chemical properties of halogens

Halogens - this is the designation for the elements of the periodic chemical table located in the seventeenth group. The peculiarity is that they react with almost all substances of a simple type, excluding only certain non-metals. Since they act as energetic oxidizers, in nature they mix with other substances. The chemical activity of halogens directly depends on the atomic number.

General information about halogens

These elements are called halogens: fluorine, chlorine, bromine, iodine and astatine. All of them belong to pronounced non-metals. Only in iodine can, under certain circumstances, be found the properties attributed to metals.

The term “halogen” was originally used in 1811 by the German scientist I. Schweigger, which literally translates from Greek as “solar.”

Being in the main state electronic configuration of halogen atoms is the following - ns 2 np 5, where the letter n marks the main quantum number or period. If we compare the chlorine atom with other halogens, it will be noticeable that its electrons are weakly shielded from the nucleus, which is why it is characterized by a high specific electron density and a smaller radius, and also has high ionization energy and electronegativity.

Fluorine (F) is an element available in the form of salts that are dispersed in various rocks. The most important compound is the mineral fluorite and fluorspar. The mineral cryolite is also well known.

Chlorine (Cl) is the most common halogen. Its most important natural compound is sodium chloride, which is used as the main raw material if other chloride compounds are needed. Sodium chloride is mostly distributed in the waters of seas and oceans, but it can also be found in some lakes. This halogen can also be found in solid form, the so-called rock salt.

Bromine (Br) - in nature, it appears as sodium and potassium salts paired with chloride salts. Typically found in salt lakes and seas.

Iodine (J) is a chemical element that is also often found in sea water, but in very small quantities, so isolating it from moisture is a rather difficult procedure. Note that there is certain type seaweed - kelp, iodine accumulates in their tissues. Iodine is extracted from the ash of these algae. Iodine can also be found in drilling waters that lie underground.

Astatine (At) is a chemical element practically not found in nature. To extract it, nuclear reactions are carried out artificially. Astatine has the longest-lived isotope, with a half-life of 8.3 hours.

Chemical characteristics of halogens

When asking the question, halogens - what are they, you should answer that these are all elements of the periodic table, where each has its own indicator of chemical activity. When considering the latter for fluorine, it should be noted that it is the highest. Academician A.E. Fersman calls fluoride all-consuming. So, if we take room temperature, then iron, lead and alkali metals will burn in a fluorine atmosphere.

Important! Fluorine has no effect on certain metals (copper, nickel), on the surface of which protective layer in the form of fluoride. But if you heat fluorine, a reaction begins to appear.

Let us note the reaction of fluorine to many non-metals, including hydrogen, iodine, carbon, boron and others. In cold conditions, corresponding compounds are formed that can lead to an explosion or flame. Fluorine is not able to react only to oxygen, nitrogen and carbon (the latter must be in the form of diamond).

A very energetic reaction has been observed to complex substances. Even fairly persistent substances in the form of glass (wool) and water vapor burn in a fluorine atmosphere. It should be noted that fluorine cannot be dissolved in water, since it is capable of vigorously dissolving it.

Note! Fluorine is the strongest oxidizing agent.

Each halogen compound has its own characteristics, for example, chlorine also has a noticeable high chemical activity, although inferior to fluorine. This element is capable of affecting all simple substances, excluding only oxygen, nitrogen and noble gases. Under high temperature conditions, the following non-metals: phosphorus, arsenic, silicon and antimony react with chlorine and release a large number of heat. At room temperature and without light, chlorine has little effect on hydrogen, but if it is heated or bright sunlight is added, the reaction can cause an explosion.

The reaction of chlorine to water is as follows: hydrochloric and hypochlorous acid are formed. If phosphorus is added to chlorine, the latter will ignite, resulting in the formation of phosphorus trichloride and pentachloride.

To obtain chlorine, it is necessary to carry out electrolysis of concentrated aqueous solutions of NaCl. Chlorine will begin to be released from the carbon anode, and hydrogen will begin to be released at the cathode. Using chlorine, hydrogen chloride and hydrochloric acid are obtained, which are used to bleach paper and fabrics and, if necessary, to disinfect drinking water.

Halogen compounds with bromine have lower chemical activity than with chlorine. Bromine and hydrogen combine only under heating conditions. To obtain bromine it is necessary to oxidize HBr. IN industrial conditions bromides and chloride solution. In Russia, the main source of bromine is underground drilling waters and saturated solutions of certain salt lakes.

Iodine has an even lower level of chemical reactivity than other halogen compounds. Despite its lower activity, this element is also capable of reacting with many non-metals under normal conditions, resulting in the formation of salts (if you pay attention, the word “halogen” comes from the words “the birth of salt”).

The reaction of iodine with hydrogen requires quite high heat. The reaction itself is incomplete, as liquid hydrogen begins to decompose.

Comparing halogen compounds, it is noted that their activity becomes less from fluorine to astatine. The peculiarity of halogens is that they react with many simple substances. In the case of metals it is observed fast reaction, which releases a large amount of heat.

Features of the extraction and use of halogens

Under natural conditions, halogens are anions, therefore, to obtain free halogens, the method of oxidation by electrolysis or using oxidizing agents is used. For example, to obtain chlorine, it is necessary to hydrolyze the solution table salt. Halogen compounds are used in many industries:

• Fluorine. Despite its high reactivity, this chemical element is often used in industry. For example, fluorine - key element Teflon and other fluoropolymers. Also available as organic chemical substances Consider chlorofluorocarbons, previously used as refrigerants and propellants in aerosols. They were subsequently discontinued because they were likely to affect environment. Fluoride is often found in toothpaste to help maintain the integrity of teeth. This halogen can also be found in clay, where it is relevant for the production of ceramics;
• Chlorine. Most frequent use chlorine – disinfection drinking water and swimming pools. And a compound called sodium hypochlorite is the main component of bleach. Industrial structures and laboratories cannot do without the use of of hydrochloric acid. Polyvinyl chloride also contains fluorine, as do other polymers used to insulate pipes, wiring and other communications. Chlorine has also been used in pharmaceuticals, where it is used to produce medicines that treat infections, allergies and diabetes. As noted above, chlorine disinfects well, so hospital equipment is sterilized with its help;
• Bromine. main feature of this chemical element is that it is non-flammable. For this reason, it has been successfully used to suppress combustion. Bromine, combined with other elements, was used for production at the same time special means for the garden, thanks to which all bacteria died. But over time, the remedy was banned with the pretext that the latter had negative impact on ozone layer planets. Bromine is also relevant in the following areas: the production of gasoline, the production of photographic film, fire extinguishers and some medicines;
• Iodine. An important chemical element on which the proper functioning of the thyroid gland depends. Due to a lack of iodine in the body, the latter may even begin to increase in size. Iodine has proven itself to be excellent antiseptic. Iodine is found in solutions used to clean wounds;
• Astatine This halogen is not only rare earth, but also radioactive, for this reason it is not particularly used.

Halogens and their physical properties

The presence of certain chemicals and physical properties directly depends on the atomic structure of the element. For the most part, all halogens have similar properties, but they still have certain features:

• Fluorine. An element in the form of a light green gas with poisonous properties;
• Chlorine. A yellow-green gas, also poisonous, with a pungent, suffocating and unpleasant smell. The element is able to easily dissolve in water, which is why chlorine water is formed;
• Bromine. Acts as the only liquid non-metal. This is a heavy element, made in red-brown color. If bromine is placed in any vessel, the walls of the latter will turn red-brown, released with halogen vapor. The smell of bromine is heavy and unpleasant. To store bromine, special bottles with ground stoppers and caps are used. It is important to note that the latter should not be made of rubber, since the element can easily corrode this material;
• Iodine. Dark gray crystalline substance, in vapors having purple. Normal conditions do not make it possible to bring iodine into a state of melting, much less boiling, since even slight heating of the element leads to its sublimation: when it goes from a solid to a gaseous state. This property is possessed not only by iodine, but also by some other substances. This property was useful in purifying substances from impurities. Iodine is one of those elements that is poorly soluble in water. The latter gets a light yellow color. Iodine can dissolve especially well in alcohol, as a result of which they began to make a 5-10% iodine solution, called iodine tincture.

Halogen compounds and their role in the human body

When choosing a toothpaste, many people pay attention to the composition: does it contain fluoride. This component is added for a reason, because it is what helps build tooth enamel and bones, and can also make teeth more resistant to caries. Metabolic processes also cannot do without the help of fluoride.

In the human body, chlorine also plays an important role, actively participating in maintaining the water-salt balance, as well as maintaining osmotic pressure. Thanks to chlorine, metabolism and tissue construction function more efficiently. It is hydrochloric acid that promotes better digestion, without which it would be impossible to digest food.

Chlorine is essential for the human body and must be supplied to it in certain quantities. If you neglect the rate of entry of the element into the body, you may encounter swelling, headaches and other unpleasant sensations.

Bromine is found in small quantities in the brain, kidneys, blood and liver. In medicine, bromine is an excellent sedative. However, it must be given in strict proportions, since the consequences of an overdose are not the best: a depressed state of the nervous system.

Iodine is strictly necessary for the thyroid gland, helping the latter to actively fight bacteria entering the body. If there is not enough iodine in the human body, thyroid disease may begin.

As a conclusion, we note that halogens are necessary not only for the implementation of many everyday things, but also for the effective functioning of our body. These chemical elements have certain characteristics that find their application in various sectors of human life.

Video

Chemistry of Elements

Nonmetals of VIIA subgroup

Elements of the VIIA subgroup are typical nonmetals with high

electronegativity, they have a group name - “halogens”.

Main issues covered in the lecture

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

oxidation penalties. Features of the chemistry of halogens.

Simple substances.

Natural compounds.

Halogen compounds

Hydrohalic acids and their salts. Salt and hydrofluoric acid

slots, receipt and application.

Halide complexes.

Binary oxygen compounds of halogens. Instability approx.

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 shell

boxes, that's why they have there is a strong tendency towards

addition of an electron.

All elements easily form simple single-charge

ny anions G – .

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, sylvite KCl, fluorite

CaF2.

General group name of elements VIIA-

group “halogens”, i.e. “giving birth to salts”, is due to the fact that most of their compounds with metals are pre-

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

which can be obtained through direct interaction

interaction of metal with 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

for all halogens.

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

The most important characteristics of atoms of elements of group VIIA

Halogens have a high electron affinity (maximum at

Cl) and very great energy ionization (maximum at F) and maximum

possible electronegativity in each period. Fluorine is the most

electronegative of all chemical elements.

The presence of one unpaired electron in halogen atoms determines

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

For simple substances, halogens, the most characteristic oxidizing agents are

properties, which are strongest in F2 and weaken when moving to I2.

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

has extremely high activity.

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

other elements of the subgroup. This general pattern for all non-metals.

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

resident oxidation states. In any connection, including with ki-

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

All other halogens exhibit positive oxidation degrees

leniya 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.

Cl has known oxides in which it is found in oxidation states: +4 and +6.

The most important halogen compounds, in positive states,

Penalties of oxidation are oxygen-containing acids and their salts.

All halogen compounds in positive oxidation states are

are strong oxidizing agents.

terrible degree of oxidation. Disproportionation is promoted by an alkaline environment.

Practical application of simple substances and oxygen compounds

The reduction of halogens is mainly due to their oxidizing effect.

Widest practical use find simple substances Cl2

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

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

pesticides, drugs. Significant amount chlorine and iodine are used to obtain metals and for their refining. Chlorine is also used

for bleaching cellulose, for disinfecting drinking water and in production

water of bleach and hydrochloric acid. Salts of oxoacids are used in the production of explosives.

Acids—hydrochloric and molten acids—are widely used in practice.

Fluorine and chlorine are among the twenty most common elements

there, there is significantly less bromine and iodine in nature. All halogens occur in nature in their oxidation state(-1). Only iodine occurs in the form of the salt KIO3,

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

Astatine is an artificially produced 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 cancer 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

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

intermolecular interaction, leading to a change in aggregate co-

standing under standard conditions.

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

liquid state.

Chlorine is a yellow-green gas that turns into liquid at –34o C. With the 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 increased intermolecular interaction.

Bromine is a dark red, very volatile liquid, boils at 58.8o C.

the name of the element is associated with the sharp unpleasant odor of gas and is derived from

"bromos" - "smelly".

Iodine – dark purple crystals, with a faint “metallic”

lumps, which when heated easily sublimate, forming violet vapors;

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

"iodos" - "purple".

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 the First World War, chlorine was used as a poisonous agent.

Fluorine gas and liquid bromine cause skin burns. Working with ha-

logens, precautions should be taken.

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

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

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

The solution reaches 0.2 mol/l, and chlorine – 0.1 mol/l.

Fluoride decomposes water:

2F2 + 2H2 O = O2 + 4HF

Halogens exhibit high oxidative activity and transition

into halide anions.

Г2 + 2e–  2Г–

Fluorine has especially 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, e.g.

water, quartz (SiO2).

SiO2 + 2F2 = SiF4 + O2

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

nic acid, act as reducing agents, while fluorine oxidizes the input

containing O(–2) in their composition.

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 we use

There are nickel and copper, which, when oxidized, form dense protective films of fluorides on their surface. The name F is due to its aggressive action.

I eat, it comes from the Greek. “fluoros” – “destructive”.

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

increasing the size of atoms and decreasing electronegativity.

In aqueous solutions, the oxidative and reductive properties of matter

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

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

carbon is the most common oxidizing agent.

Standard electrode potentials for simple halogen substances

Reduced oxidative activity

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

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

recovering to F–. Judging by the Eо value, 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 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 characterized by even greater stability in water.

Disproportionation is a very characteristic oxidative

reduction reaction for halogens. Disproportionation of the amplification

pours 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 disproportioned in alkali, I– and IO3– are formed. Ana-

Logically, Br2 disproportionates iodine. Product change is disproportionate

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

The chlorine disproportionation reaction is used in industrial

ability to obtain a strong and fast-acting hypochlorite oxidizer,

bleaching lime, bertholet salt.

3Cl2 + 6 KOH = 5KCl + KClO3 + 3H2 O

Interaction of halogens with metals

Halogens react 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),

- These are salt-like compounds with predominantly ionic bonds. How to

lo, ionic halides are solids with a high melting point

Metal halides in which the metal has a high degree of oxidation

tions are compounds with predominantly covalent bonds.

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

TiCl4 is liquid.

Interaction of halogens with non-metals

Halogens interact directly with many nonmetals:

hydrogen, phosphorus, sulfur, etc. For example:

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

The bonding in nonmetal halides is predominantly covalent.

Typically these compounds have low melting and boiling points.

When passing from fluorine to iodine, the covalent nature of the halides increases.

The covalent halides of typical nonmetals are acidic compounds; when interacting with water, they hydrolyze to form acids. For example:

PBr3 + 3H2 O = 3HBr + H3 PO3

PI3 + 3H2 O = 3HI + H3 PO3

PCl5 + 4H2 O = 5HCl + H3 POinterga-

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

oxidation penalties.

Due to the direct interaction of halogens upon heating, 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 temperatures boiling. Interhalides have a high oxidative activity

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

2Al2 O3 + 4ClF3 = 4 AlF3 + 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 hydrolyze to form acids. For example,

ClF5 + 3H2 O = 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 halogen

Nid ions.

2Г –  Г2 + 2e–

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

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

GENERAL CHARACTERISTICS

Halogens (from the Greek halos - salt and genes - forming) - elements main subgroup Group VII of the periodic system: fluorine, chlorine, bromine, iodine, astatine.

Table. Electronic structure and some properties of halogen atoms and molecules

1) The general electronic configuration of the outer energy level is nS2nP5.
2) With an increase in the atomic number of elements, the radii of atoms increase, electronegativity decreases, non-metallic properties weaken (metallic properties increase); halogens are strong oxidizing agents, the oxidizing ability of elements decreases with increasing atomic mass.
3) Halogen molecules consist of two atoms.
4) With an increase in atomic mass, the color becomes darker, the melting and boiling points, as well as density, increase.
5) The strength of hydrohalic acids increases with increasing atomic mass.
6) Halogens can form compounds with each other (for example, BrCl)

FLUORINE AND ITS COMPOUNDS

Fluorine F2 - discovered by A. Moissan in 1886.

Physical properties

The gas is light yellow in color; t°melting= -219°C, t°boiling= -183°C.

Receipt

Electrolysis of potassium hydrofluoride melt KHF2:

Chemical properties

F2 is the strongest oxidizing agent of all substances:

1. 2F2 + 2H2O ® 4HF + O2
2. H2 + F2 ® 2HF (with explosion)
3. Cl2 + F2 ® 2ClF

Hydrogen fluoride

Physical properties

Colorless gas, highly soluble in water, mp. = - 83.5°C; t°boil. = 19.5°C;

Receipt

CaF2 + H2SO4(conc.) ® CaSO4 + 2HF

Chemical properties

1) A solution of HF in water - weak acid (hydrofluoric):

HF « H+ + F-

Hydrofluoric acid salts - fluorides

2) Hydrofluoric acid dissolves glass:

SiO2 + 4HF ® SiF4+ 2H2O

SiF4 + 2HF ® H2 hexafluorosilicic acid

CHLORINE AND ITS COMPOUNDS

Chlorine Cl2 - discovered by K. Scheele in 1774.

Physical properties

Gas yellow-green color, mp. = -101°C, t°boil. = -34°C.

Receipt

Oxidation of Cl- ions with strong oxidizing agents or electric current:

MnO2 + 4HCl ® MnCl2 + Cl2 + 2H2O
2KMnO4 + 16HCl ® 2MnCl2 + 5Cl2 + 2KCl + 8H2O
K2Cr2O7 + 14HCl ® 2CrCl3 + 2KCl + 3Cl2 + 7H2O

electrolysis of NaCl solution (industrial method):

2NaCl + 2H2O ® H2 + Cl2 + 2NaOH

Chemical properties

Chlorine is a strong oxidizing agent.

1) Reactions with metals:

2Na + Cl2 ® 2NaCl
Ni + Cl2 ® NiCl2
2Fe + 3Cl2 ® 2FeCl3

2) Reactions with non-metals:

H2 + Cl2 –hn® 2HCl
2P + 3Cl2 ® 2PClЗ

3) Reaction with water:

Cl2 + H2O « HCl + HClO

4) Reactions with alkalis:

Cl2 + 2KOH –5°C® KCl + KClO + H2O
3Cl2 + 6KOH –40°C® 5KCl + KClOЗ + 3H2O
Cl2 + Ca(OH)2 ® CaOCl2(bleach) + H2O

5) Displaces bromine and iodine from hydrohalic acids and their salts.

Cl2 + 2KI ® 2KCl + I2
Cl2 + 2HBr ® 2HCl + Br2

Chlorine compounds
Hydrogen chloride

Physical properties

A colorless gas with a pungent odor, poisonous, heavier than air, highly soluble in water (1: 400).
t°pl. = -114°C, t°boil. = -85°C.

Receipt

1) Synthetic method (industrial):

H2 + Cl2 ® 2HCl

2) Hydrosulfate method (laboratory):

NaCl(solid) + H2SO4(conc.) ® NaHSO4 + HCl

Chemical properties

1) A solution of HCl in water - hydrochloric acid - strong acid:

HCl « H+ + Cl-

2) Reacts with metals in the voltage range up to hydrogen:

2Al + 6HCl ® 2AlCl3 + 3H2

3) with metal oxides:

MgO + 2HCl ® MgCl2 + H2O

4) with bases and ammonia:

HCl + KOH ® KCl + H2O
3HCl + Al(OH)3 ® AlCl3 + 3H2O
HCl + NH3 ® NH4Cl

5) with salts:

CaCO3 + 2HCl ® CaCl2 + H2O + CO2
HCl + AgNO3 ® AgCl¯ + HNO3

The formation of a white precipitate of silver chloride, insoluble in mineral acids, is used as a qualitative reaction for the detection of Cl- anions in solution.
Metal chlorides are salts of hydrochloric acid, they are obtained by the interaction of metals with chlorine or the reactions of hydrochloric acid with metals, their oxides and hydroxides; by exchange with certain salts

2Fe + 3Cl2 ® 2FeCl3
Mg + 2HCl ® MgCl2 + H2
CaO + 2HCl ® CaCl2 + H2O
Ba(OH)2 + 2HCl ® BaCl2 + 2H2O
Pb(NO3)2 + 2HCl ® PbCl2¯ + 2HNO3

Most chlorides are soluble in water (with the exception of silver, lead and monovalent mercury chlorides).

Hypochlorous acid HCl+1O
H–O–Cl

Physical properties

Exists only in the form of dilute aqueous solutions.

Receipt

Cl2 + H2O « HCl + HClO

Chemical properties

HClO is a weak acid and a strong oxidizing agent:

1) Decomposes, releasing atomic oxygen

HClO – in the light® HCl + O

2) With alkalis it gives salts - hypochlorites

HClO + KOH ® KClO + H2O

2HI + HClO ® I2¯ + HCl + H2O

Chlorous acid HCl+3O2
H–O–Cl=O

Physical properties

Exists only in aqueous solutions.

Receipt

It is formed by the interaction of hydrogen peroxide with chlorine oxide (IV), which is obtained from Berthollet salt and oxalic acid in H2SO4:

2KClO3 + H2C2O4 + H2SO4 ® K2SO4 + 2CO2 + 2СlO2 + 2H2O
2ClO2 + H2O2 ® 2HClO2 + O2

Chemical properties

HClO2 is a weak acid and a strong oxidizing agent; salts of chlorous acid - chlorites:

HClO2 + KOH ® KClO2 + H2O

2) Unstable, decomposes during storage

4HClO2 ® HCl + HClO3 + 2ClO2 + H2O

Hypochlorous acid HCl+5O3

Physical properties

Stable only in aqueous solutions.

Receipt

Ba (ClO3)2 + H2SO4 ® 2HClO3 + BaSO4¯

Chemical properties

HClO3 - Strong acid and strong oxidizing agent; salts of perchloric acid - chlorates:

6P + 5HClO3 ® 3P2O5 + 5HCl
HClO3 + KOH ® KClO3 + H2O

KClO3 - Berthollet salt; it is obtained by passing chlorine through a heated (40°C) KOH solution:

3Cl2 + 6KOH ® 5KCl + KClO3 + 3H2O

Berthollet's salt is used as an oxidizing agent; When heated, it decomposes:

4KClO3 – without cat® KCl + 3KClO4
2KClO3 –MnO2 cat® 2KCl + 3O2

Perchloric acid HCl+7O4

Physical properties

Colorless liquid, boiling point. = 25°C, temperature = -101°C.

Receipt

KClO4 + H2SO4 ® KHSO4 + HClO4

Chemical properties

HClO4 is a very strong acid and a very strong oxidizing agent; salts of perchloric acid - perchlorates.

HClO4 + KOH ® KClO4 + H2O

2) When heated, perchloric acid and its salts decompose:

4HClO4 –t°® 4ClO2 + 3O2 + 2H2O
KClO4 –t°® KCl + 2O2

BROMINE AND ITS COMPOUNDS

Bromine Br2 - discovered by J. Balard in 1826.

Physical properties

Brown liquid with heavy toxic fumes; has an unpleasant odor; r= 3.14 g/cm3; t°pl. = -8°C; t°boil. = 58°C.

Receipt

Oxidation of Br ions by strong oxidizing agents:

MnO2 + 4HBr ® MnBr2 + Br2 + 2H2O
Cl2 + 2KBr ® 2KCl + Br2

Chemical properties

In its free state, bromine is a strong oxidizing agent; and its aqueous solution - "bromine water" (containing 3.58% bromine) is usually used as a weak oxidizing agent.

1) Reacts with metals:

2Al + 3Br2 ® 2AlBr3

2) Reacts with non-metals:

H2 + Br2 « 2HBr
2P + 5Br2 ® 2PBr5

3) Reacts with water and alkalis:

Br2 + H2O « HBr + HBrO
Br2 + 2KOH ® KBr + KBrO + H2O

4) Reacts with strong reducing agents:

Br2 + 2HI ® I2 + 2HBr
Br2 + H2S ® S + 2HBr

Hydrogen bromide HBr

Physical properties

Colorless gas, highly soluble in water; t°boil. = -67°C; t°pl. = -87°C.

Receipt

2NaBr + H3PO4 –t°® Na2HPO4 + 2HBr

PBr3 + 3H2O ® H3PO3 + 3HBr

Chemical properties

An aqueous solution of hydrogen bromide is hydrobromic acid, which is even stronger than hydrochloric acid. It undergoes the same reactions as HCl:

1) Dissociation:

HBr « H+ + Br -

2) With metals in the voltage series up to hydrogen:

Mg + 2HBr ® MgBr2 + H2

3) with metal oxides:

CaO + 2HBr ® CaBr2 + H2O

4) with bases and ammonia:

NaOH + HBr ® NaBr + H2O
Fe(OH)3 + 3HBr ® FeBr3 + 3H2O
NH3 + HBr ® NH4Br

5) with salts:

MgCO3 + 2HBr ® MgBr2 + H2O + CO2
AgNO3 + HBr ® AgBr¯ + HNO3

Salts of hydrobromic acid are called bromides. The last reaction - the formation of a yellow, acid-insoluble precipitate of silver bromide - serves to detect the Br - anion in solution.

6) HBr is a strong reducing agent:

2HBr + H2SO4(conc.) ® Br2 + SO2 + 2H2O
2HBr + Cl2 ® 2HCl + Br2

Of the oxygen acids of bromine, the weak brominated acid HBr+1O and the strong brominated acid HBr+5O3 are known.
IODINE AND ITS COMPOUNDS

Iodine I2 - discovered by B. Courtois in 1811.

Physical properties

Crystalline substance of dark purple color with a metallic luster.
r= 4.9 g/cm3; t°pl.= 114°C; boiling point = 185°C. Very soluble in organic solvents (alcohol, CCl4).

Receipt

Oxidation of I-ions by strong oxidizing agents:

Cl2 + 2KI ® 2KCl + I2
2KI + MnO2 + 2H2SO4 ® I2 + K2SO4 + MnSO4 + 2H2O

Chemical properties

1) with metals:

2Al + 3I2 ® 2AlI3

2) with hydrogen:

3) with strong reducing agents:

I2 + SO2 + 2H2O ® H2SO4 + 2HI
I2 + H2S ® S + 2HI

4) with alkalis:

3I2 + 6NaOH ® 5NaI + NaIO3 + 3H2O

Hydrogen iodide

Physical properties

Colorless gas with a pungent odor, highly soluble in water, boiling point. = -35°С; t°pl. = -51°C.

Receipt

I2 + H2S ® S + 2HI

2P + 3I2 + 6H2O ® 2H3PO3 + 6HI

Chemical properties

1) A solution of HI in water - strong hydroiodic acid:

HI « H+ + I-
2HI + Ba(OH)2 ® BaI2 + 2H2O

Salts of hydroiodic acid - iodides (for other HI reactions, see the properties of HCl and HBr)

2) HI is a very strong reducing agent:

2HI + Cl2 ® 2HCl + I2
8HI + H2SO4(conc.) ® 4I2 + H2S + 4H2O
5HI + 6KMnO4 + 9H2SO4 ® 5HIO3 + 6MnSO4 + 3K2SO4 + 9H2O

3) Identification of I- anions in solution:

NaI + AgNO3 ® AgI¯ + NaNO3
HI + AgNO3 ® AgI¯ + HNO3

A dark yellow precipitate of silver iodide is formed, insoluble in acids.

Oxygen acids of iodine

Hydrous acid HI+5O3

Colorless crystalline substance, melting point = 110°C, highly soluble in water.

Receive:

3I2 + 10HNO3 ® 6HIO3 + 10NO + 2H2O

HIO3 is a strong acid (salts - iodates) and a strong oxidizing agent.

Iodic acid H5I+7O6

Crystalline hygroscopic substance, highly soluble in water, melting point = 130°C.
Weak acid (salts - periodates); strong oxidizing agent.

From a chemistry textbook, many people know that halogens include chemical elements of the periodic system of Mendeleev from group 17 in the table.

Translated from Greek as birth, origin. Almost all of them are highly active, due to which they react violently with simple substances, with the exception of a few non-metals. What are halogens and what are their properties?

List of halogens

Halogens are good oxidizing agents; for this reason, in nature they can only be found in some compounds. The higher serial number, the less chemical activity of the elements of this group. The halogen group includes the following elements:

• chlorine (Cl);
• fluorine (F);
• iodine (I);
• bromine (Br);
• astatine (At).

The latter was developed at the Institute of Nuclear Research, which is located in the city of Dubna. Fluorine is a poisonous gas with a pale yellow color. Chlorine is also poisonous. This is a gas that has a rather pungent and unpleasant odor of light green color. Bromine has a reddish-brown color and is a toxic liquid that can even affect the sense of smell. It is very volatile, so it is stored in ampoules. Iodine is a crystalline, easily sublimated, dark purple substance. Astatine is radioactive, crystal color: black with blue, half-life is 8.1 hours.

The high oxidation activity of halogens decreases from fluorine to iodine. The most active of its brethren is fluorine, which has the ability to react with any metals, forming salts, some of them spontaneously ignite, releasing a huge amount of heat. Without heating, this element reacts with almost all non-metals, reactions are accompanied by the release of a certain amount of heat (exothermic).

Fluorine interacts with inert gases and is irradiated (Xe + F 2 = XeF 2 + 152 kJ). When heated, fluorine affects other halogens, oxidizing them. The formula holds: Hal 2 + F 2 = 2HalF, where Hal = Cl, Br, I, At, in the case when HalF oxidation states of chlorine, bromine, iodine and astatine are equal to + 1.

Fluorine also interacts quite vigorously with complex substances. The consequence is water oxidation. In this case, an explosive reaction occurs, which is briefly written by the formula: 3F 2 + ZH 2 O = OF 2 + 4HF + H 2 O 2.

Chlorine

The activity of free chlorine is slightly less than fluorine, but it also has a good ability to react. This can occur when interacting with many simple substances, with rare exceptions in the form of oxygen, nitrogen, and inert gases. He can react violently with complex substances, creating substitution reactions, the property of adding hydrocarbons is also inherent in chlorine. When heated, bromine or iodine is displaced from compounds with hydrogen or metals.

This element has a peculiar relationship with hydrogen. At room temperature and without light, chlorine does not react in any way to this gas, but as soon as it is heated or directed at light, an explosive chain reaction will occur. The formula is given below:

Cl2+ hν → 2Cl, Cl + H2 → HCl + H, H + Cl2 → HCl + Cl, Cl + H2 → HCl + H, etc.

Photons, when excited, cause the decomposition of Cl 2 molecules into atoms, and a chain reaction occurs, causing the appearance of new particles that initiate the beginning of the next stage. In the history of chemistry this phenomenon has been studied. Russian chemist and laureate Nobel Prize Semenov N.N. in 1956 he studied the photochemical chain reaction and thereby made a great contribution to science.

Chlorine reacts with many complex substances, these are substitution and addition reactions. It dissolves well in water.

Cl 2 + H 2 O = HCl + HClO - 25 kJ.

With alkalis, when heated, chlorine can disproportionate.

Bromine, iodine and astatine

The chemical activity of bromine is slightly less than that of the above-mentioned fluorine or chlorine, but it is also quite high. Bromine is often used in liquid form. It, like chlorine, dissolves very well in water. A partial reaction occurs with it, allowing one to obtain “bromine water”.

The chemical activity of iodine is noticeably different from other representatives of this series. It almost does not interact with non-metals, but with With metals the reaction occurs very slowly and only when heated. In this case, a large absorption of heat occurs (endothermic reaction), which is highly reversible. Besides Iodine cannot be dissolved in water in any way, this cannot be achieved even with heating, which is why “iodine water” does not exist in nature. Iodine can only be dissolved in iodide solution. In this case, complex anions are formed. In medicine, this compound is called Lugol's solution.

Astatine reacts with metals and hydrogen. In the series of halogens, chemical activity decreases in the direction from fluorine to astatine. Each halogen in the F - At series is capable of displacing subsequent elements from compounds with metals or hydrogen. Astatine is the most passive of these elements. But it is characterized by interaction with metals.

Application

Chemistry is firmly entrenched in our lives, penetrating into all areas. Man has learned to use halogens, as well as its compounds, for his own benefit. The biological significance of halogens is undeniable. Their areas of application are different:

• medicine;
• pharmacology;
• production of various plastics, dyes, etc.;
• Agriculture.

Made from a natural compound of cryolite, chemical formula which looks like this: Na3AlF6, get aluminum. Fluorine compounds are widely used in production toothpastes. Fluoride is known to help prevent caries. Alcohol tincture of iodine is used for disinfection and disinfection of wounds.

Chlorine has found the most widespread use in our lives. The scope of its application is quite diverse. Examples of using:

1. Production of plastics.
2. Obtaining hydrochloric acid.
3. Production of synthetic fibers, solvents, rubbers, etc.
4. Bleaching of fabrics (linen and cotton), paper.
5. Disinfection of drinking water. But ozone is increasingly used for this purpose, since the use of chlorine is harmful to the human body.
6. Disinfection of premises

It must be remembered that halogens are very toxic substances. This property is especially pronounced in fluorine. Halogens can cause asphyxiation, respiratory irritation and damage biological tissue.

Chlorine vapors can be extremely dangerous, as well as fluorine aerosol, which has a faint odor and can be felt in high concentrations. A person may experience a suffocation effect. When working with such connections, precautions must be taken.

The methods for producing halogens are complex and varied. In industry, this is approached with certain requirements, the observance of which is strictly observed.

All elements periodic table Mendeleev is grouped into groups depending on their chemical properties. In this article we will look at what halogens (or halogens) are.

The meaning of halogens

Halogens are elements from the periodic table of group 17 of Mendeleev, and according to the outdated classification - 7 of the main subgroup. The halogens include only 5 chemical elements, including fluorine, chlorine, iodine, astatine and bromine. All of them are non-metals. Halogens are very active oxidizing agents, and external level These elements have 7 electrons.

What are halogens, why did they get this name? The word "halogen" comes from two Greek words that together mean "the birth of salt." One of the elements in this group, chlorine, forms a salt together with sodium.

Physical properties of the halogen group

Similar, but different physical characteristics elements are different from each other.

Fluorine is a yellow gaseous substance with a very unpleasant and pungent odor. Chlorine is a green-yellow gas with a heavy and repulsive odor. Bromine - liquid Brown. Astatine - blue-black solid with a pungent odor. Iodine - gray Summarizing the above information, we can answer the question: “What are halogens?” These include gases, liquids, and solids.

Chemical properties of the halogen group

The main common property of all halogens is that they are all very active oxidizing agents. The most active halide is fluorine, which reacts with all metals, and the most inactive is astatine.

Interaction with halogens in simple substances (with the exception of some non-metals) occurs easily. In nature they are found only in the form of compounds.

Fluorine

Such as fluorine was obtained only at the end of the 19th century by a French scientist named Henri Moissan. Fluorine is a pale yellow gas. Halogens are typical non-metals and oxidizing agents, and fluorine is the most active of all halogens. Now this halogen is indispensable in industry because it is used in the manufacture of pipes, electrical tape, and various fabric coverings, non-stick surfaces for frying pans and molds, and in medicine in the manufacture of artificial arteries and veins. In industry, this halogen is diluted with nitrogen.

Chlorine

Chlorine is a famous chemical element that belongs to the group of halogens. We discussed above what halogens are. Chlorine retains the basic properties of the elements of its group.

It got its name from Greek word"chloros", which translates to pale green. This gas is very widespread in nature and is found in large quantities in sea water. Chlorine is a very important chemical element; it is practically indispensable for bleaching, disinfecting swimming pools, and disinfecting drinking water.

But chlorine is also known for being a deadly weapon. In 1915, German troops used about 6 thousand cylinders of this halogen against the French army. This deadly weapon was invented by the famous German chemist Fritz Haber.

Iodine

Iodine, or iodine, is another chemical element that belongs to the halogen group. In fact, in the periodic table this element is called nothing more than iodine, but its trivial name is considered to be iodine. The name of the element comes from the Greek word, which translated into Russian means “violet”. This chemical element is Everyday life occurs quite often. When reacted with other halogens, mainly chlorine, it produces an excellent disinfectant for wounds and scratches. Now iodine is used in medicine to prevent thyroid diseases.

Astatine

Astatine is interesting because it has never been produced by chemists in such quantities that it can be seen with the naked eye. And most likely, this opportunity will never present itself to them. Even if specialists were able to obtain a large amount of this chemical element, it would immediately evaporate due to the high temperature that appears as a result of the radioactive radiation of this element. Astatine is the rarest chemical element, and small amounts are found in the earth's crust.

Among the halogens, astatine is a rather useless element, because at the moment no use has been found for it.

Application and meaning

Despite the fact that all halogens have similar chemical properties, they are used completely in different areas. For example, fluoride is very beneficial for teeth, which is why it is added to toothpastes. The use of therapeutic and prophylactic agents that contain the chemical element fluorine prevents the occurrence of caries. Chlorine is used to produce hydrochloric acid, which is indispensable in industry and medicine. Chlorine is used to make rubber, plastics, solvents, dyes, and synthetic fibers. Compounds containing this element are used in agriculture for pest control. Halogen chlorine is indispensable for bleaching paper and fabrics. The use of chlorine to treat drinking water is considered unsafe. Bromine, which is a halogen, and iodine are often used in medicine.

The importance of halogens in human life is enormous. If we imagine the existence of humanity without halogens, then we would be deprived of such things as photographs, antiseptic and disinfectants, rubber, plastic, linoleum and many others. In addition, these substances are necessary for the human body to function normally, that is, they play an important biological role. Although the properties of halogens are similar, their role in industry and medicine is different.

Return