slide 3

slide 4

VELES - the god of wildlife and animals PERUN - the creator of earthly crops, the giver of food, the establisher and patron of agriculture.

slide 5

Water Goblin

slide 6

The limited number of people living on the planet made it possible to satisfy their needs without resorting to significant changes in nature.

Slide 7

Slide 8

In the 20th century, relations with nature deteriorated significantly.

Slide 9

Thanks to the huge number of drugs, fewer and fewer diseases are classified as incurable. At the same time, new diseases associated with the consequences of the use of drugs, such as allergies, have appeared.

Slide 10

gmo

Genetically modified products bring huge economic benefits, BUT they cause environmental damage, affecting variety formation and, possibly, human health. 10

slide 11

Peaceful atom?

Usage nuclear power plants brings economic benefit and environmental harm.

slide 12

And now guys, try to formulate the problem that we will deal with in the lesson.

FLUORINE AND ITS COMPOUNDS

slide 13

So, the topic of our lesson: “FLUORINE COMPOUNDS. BENEFIT AND HARM".

Slide 14

I propose to discuss the problem of using fluorine compounds in the form of a court.

JUDGE Clerk of the Jury You can address the judge with the words: "Your Honor." During the process, the judge can give the word to the team or take it away. All questions can be answered by the Registrar of the Court. The jurors are required to choose a foreman, closely monitor the progress of the process, and at the end of the meeting, issue their verdict. lawyers accusers

slide 15

For familiarization with the case, the Court provides materials on numbered sheets and instructions. The sheet number corresponds to the token number you pulled out when you entered the class. Time to familiarize yourself with the case and prepare for the presentation is 10 minutes. Instructions are included with each case.

slide 16

Court Rules

The court will consider only scientifically proven facts. Every performance is needed. start with the words: My position ... Rationale ... Example ... Therefore ... During the process, the judge can give you a word or take it away. Jurors are required to closely monitor the progress of the process and give their opinion on this issue.

Slide 17

instructions

Disassemble the sheets with the proposed material on the properties of Fluorine in accordance with the token number. Choose a group leader. Discuss the assignment together. Define a topic. From the proposed facts, choose the most significant, to use them as arguments to defend your point of view. Distribute responsibilities (make a poster, write a slogan). Note the facts that will not be included in the speech, but are of interest. Determine the order of speeches Each speech should begin with the words: My Position .... Justification - (argument) ... Example - (facts illustrating the argument); Therefore (conclusion) You can address the Judge with the words: “Your Honor.” The Judge can give the word to the team or deprive it.

Slide 18

For example:

Your Honor, (Position) I advocate the use of Fluorine compounds (Rationale) because Fluorine is vital necessary element for the body. (Example) In case of insufficient (less than 0.5 mg/l of drinking water) consumption of Fluorine, various dental diseases can develop in the body. (Hence) I believe Fluorine compounds are beneficial. OR: (Position) Your Honor, I am in favor of banning the use of Fluorine, (Rationale) because Fluoride is a neurotropic poison (Example) Excessive amounts of Fluorine disrupt the body's metabolic processes, inhibit tissue respiration (Hence) Fluorine compounds should not be used in industry.

Slide 19

Positions are defended in the form of a "Live Line"

Lines are drawn along the diagonals of the class, on which marks are applied at the same distance. Each of the students, speaking with his point of view, if approved by the Judge, moves forward one mark. A circle is depicted on the floor in the center of the class, to which a representative of each of the groups must reach.

Slide 20

"live line"

slide 21

Create a poster

Drawings corresponding to the facts under consideration are attached to the materials of each case. To make a poster, it is necessary to choose from the proposed drawings the one that corresponds to the fact chosen for voicing Cut out the drawing and stick it on an A3 sheet Write a slogan (idea, main idea)

slide 22

Summarizing.

Next comes the discussion. Secretary: Your Honor, it so happens that the number of arguments for using Fluorine is equal to the number of arguments against using it, and the posters made by the groups perfectly reflect the team's point of view. Judge: I propose to hear the opinion of the Jury. The Foreman of the Jury is speaking... Judge: Leaders of the groups, do you agree with this decision of the Jury? Answer of the Group Leaders... Judge: Now let's hear our distinguished Jurors:...

slide 23

Group work analysis:

Teacher: Guys, today we had an unusual lesson. What was unusual about him? Answers... Teacher: Do you have any position regarding the use of scientific achievements, in particular, the use of fluorine compounds? Answers... Teacher: Then let's evaluate our work using the "Rating Rules" that are on your tables. Now show what you got. Well done! Thanks to all! It was a pleasure to work with you.

View all slides

On store shelves, we tend to see fluoridated toothpastes or mouthwashes. However, many people in recent times try to avoid such hygiene products. Consumers are hesitant about the health benefits of sodium fluoride due to some of the information being released about this supplement. And this despite the assurances of a number of dentists about the importance of fluoride for tooth enamel. Why is this happening?
Have you ever wondered why fluorinated toothpastes have label warnings such as: “Recommended for children under 6 to use toothpaste pea-sized and under adult supervision", "Do not swallow", "If fluoride is ingested, seek medical attention", etc.
The reason toothpastes have warning labels is to protect their manufacturers from fluoride poisoning lawsuits. Fluoride-free toothpastes usually don't have these warning labels because they don't have ingredients that can cause serious harm to the body.
Today dental pastes are fluoridated, tap water and even milk. Fluorine can be found in phosphate fertilizers, hence black and green tea (which are grown using phosphate fertilizers) may contain fluorine.
And one more fact that is important to pay attention to. In a number of countries there is a ban on fluoridation of drinking water: Austria, Belgium, China, Czech Republic, Denmark, Finland, France, Germany, Hungary, India, Israel, Japan, Luxembourg, the Netherlands, Northern Ireland, Norway, Scotland, Sweden, Switzerland.
And this is not at all accidental. When in these countries they learned about the "benefit" of fluorine, they immediately made the necessary decision at the legislative level - they banned its use. Since you now have a greater understanding of the reason for the warning labels on fluoridated toothpastes, let's look at the differences between natural and synthetic fluoride so you know which fluoride to avoid.

Differences between natural and synthetic fluorine

The natural sample of fluoride is not the same as the synthetic industrial version (sodium fluoride). The fluoride found in nature is known as calcium fluoride. This natural mineral is found in nature in the form of fluorite mainly in the earth's crust and groundwater at low levels.

The synthetic version of fluoride is called sodium fluoride, which is a by-product of the phosphate industry. When we are talking About this synthetic industrial variant, the term "fluoride" is used to refer to the many different chemicals that make up fluoride, including but not limited to: lead, aluminum, cadmium, arsenic, hydrofluorosilicic acid, and even radioactive materials.
During Nazi Germany, sodium fluoride was given to prisoners in concentration camps, because Nazi doctors discovered that its ingredients had a lobotomy effect on prisoners, making them more submissive and easier to control.
Have you ever heard that many experts link sodium fluoride to lower IQs and more cancers? Could this toxin really be one of the main causes of these problems?

Why It's Important to Reduce Your Sodium Fluoride Intake

If you are using fluoridated toothpaste, it is imperative that you exercise caution in controlling the amount you use when brushing your teeth, as calcium fluoride can bioaccumulate in the body.
Fluoride can gradually accumulate in the body, which eventually leads to health problems. The accumulation of fluoride accelerates with age, which sooner or later makes itself felt in the form of the development of degenerative diseases. Many experts advise avoiding fluoride as much as possible.
A synthetic version of fluoride has also been found in Russia in drinking water and milk!!! Water is fluoridated in Russia!

Fluoridation is one of the operations used in the preparation of drinking water. It is carried out at water treatment plants. Sodium fluorosilicic acid, sodium fluoride, ammonium fluorosilicic acid, hydrofluorosilicic acid are used as reagents for water fluoridation.
A new study published in the journal Environmental Health Perspectives confirms that fluoridated water causes brain damage in children.
"This is the 24th study done by this association," explained Paul Connett, Ph.D., director of the Fluoride Action Network (FAN). “This study has strengths compared to previous studies because the authors controlled for key variables together with additional correlation, and found that IQ decline in children is directly related to the fluoride content in the water and blood of children…”
"In this study, we found a significant dose-response relationship between serum fluoride levels and children's IQ," the study authors say.
Although there have been numerous studies over the years to identify fluoride as a neurotoxin, most of the mainstream medical professionals in the US ignored these studies and continue to support the idea of ​​water fluoridation. But the evidence continues to mount, and sooner or later the medical community will have to listen to the truth about fluoride.

Organ damage caused by fluoride

If sodium fluoride is consumed daily, the body becomes contaminated with this synthetic toxin, which can lead to various types health problems, including but not limited to heart disease and calcification of the pineal gland.
The brain is very sensitive to sodium fluoride, especially the pineal gland, located in the region of the quadrigemina of the midbrain. It is responsible for the production of melatonin, serotonin, adrenoglomerulotropin, dimethyltryptamine.

When the brain and pineal gland are too saturated big amount sodium fluoride, they cannot function properly.
Typical symptoms of fluoride toxicity are dental fluorosis, chronic fatigue, low IQ, headaches, memory loss, blurred vision, hearing loss, sleep disturbance, pineal gland calcification, and neurological problems. These health problems lead to a lack of holistic thinking, creativity and skills critical thinking.
Fluorine leads to premature aging, wrinkles, poor hair and nails. Articular cartilage wears out faster, which increases the risk of arthritis.
Fluorine promotes the retention of calcium in bone tissue, resulting in an increase in its density. But from high degree calcification, the bones become more brittle and more prone to fracture when struck or dropped. Despite the increase in bone mass, the risk of destruction is high.
Fluorine causes significant damage to the mucous membrane of the stomach, intestines, as well as the walls of arteries, veins, and the blood-brain barrier. As a result of this, calcification of the walls of blood vessels can occur, which further leads to atherosclerosis, etc.

What can be done?

Many researchers believe that fluoride does not have a safe dose. Even insignificant regular doses cause a load on the body, accelerate aging, reduce health, lead to the development chronic diseases.
Once a person stops using sodium fluoride, it becomes easier for the body to eliminate it from the body. The faster it leaves the body, the faster health will begin to improve.
Who would agree to increase the risk of a child's intellectual decline and their own, in order to reduce a small amount of dental caries? Although on this issue - the issue of caries - there is also not enough evidence.

SO:

1 Do not use fluoride toothpaste. These pastes include Paradontax with Fluoride, Colgate Maximum Caries Protection, Blend-a-Med with Active Fluoride. Here the names speak for themselves, but if you want to be 100% sure that the paste does not contain fluorine, make sure that the following compounds are not included in the composition:
- Monofluorophosphate;
- Aluminum fluoride;
- Sodium fluoride;
- Aminofluoride (also known as olaflur);
- Tin fluoride.
Toothpastes without fluoride:"President", "Splat", "Rocks", "Asepta", "New Pearl with Calcium" and a number of other toothpastes, the composition of which you can study on your own.

2 When buying milk, study the composition of the product. Do not buy milk with added sodium fluoride.

3 If possible, purchase a multi-stage water purification system that uses reverse osmosis and install it in your home. This water treatment will reduce the risk of fluoride toxicity.

Be vigilant in matters relating to your safety and the safety of your loved ones, and be healthy!

Distribution in nature

The average content of fluorine in the earth's crust is 6.25 * 10 -2% by weight; in acid igneous rocks (granites) it is 8 * 10 -2%, in basic - 3.7 * 10 -2%, in ultrabasic - 10 -2%. Fluorine is present in volcanic gases and thermal waters. The most important fluorine compounds are fluorite, cryolite and topaz. A total of 86 fluorine-containing minerals are known. Fluorine compounds are also found in apatites, phosphorites, and others. Fluorine is an important biogenic element. In the history of the Earth, the products of volcanic eruptions (gases, etc.) were the source of fluorine entering the biosphere.

Physical and Chemical properties

Gaseous fluorine has a density of 1.693 g / l (0 C and 0.1 Mn / m 2, or 1 kgf / cm 2), liquid - 1.5127 g / cm 3 (at the boiling point); t pl -219.61 ° С; t kip -188.13 ° С. The fluorine molecule consists of two atoms (F 2); at 1000 °C, 50% of the molecules dissociate, the dissociation energy is about 155±4 kJ/mol (37±1 kcal/mol). Fluorine is poorly soluble in liquid hydrogen fluoride; solubility 2.5 * 10 -3 g in 100 g HF at -70 °C and 0.4 * 10 -3 g at -20 °C; in liquid form, it is infinitely soluble in liquid oxygen and ozone. The configuration of the outer electrons of the fluorine atom is 2s 2 2р 5 . In compounds, it exhibits an oxidation state of -1. The covalent radius of the atom is 0.72A, the ionic radius is 1.33A. Electron affinity 3.62 eV, ionization energy (F F+) 17.418 eV. The high values ​​of electron affinity and ionization energy explain the strong electronegativity of the fluorine atom, the largest among all other elements. The high reactivity of fluorine determines the exothermicity of fluorination, which, in turn, is determined by the anomalously low dissociation energy of the fluorine molecule and the large values ​​of the bonding energy of the fluorine atom with other atoms. Direct fluoridation has a chain mechanism and can easily turn into combustion and explosion. Fluorine reacts with all elements except helium, neon, and argon. It interacts with oxygen in a glow discharge, forming low temperatures oxygen fluorides O 2 P 3, O 3 F 2, etc. The reactions of fluorine with other halogens are exothermic, resulting in the formation of interhalogen compounds. Chlorine reacts with fluorine when heated to 200-250 C, giving chlorine monofluoride СlF and chlorine trifluoride СlF 3 . ClF 3 is also known, obtained by fluorination of ClF 3 with high temperature and a pressure of 25 MN / m 2 (250 kgf / cm 2). Bromine and iodine ignite in a fluorine atmosphere at normal temperature, and BrF 3 , BrF 5 , IF 5 , IF 7 can be obtained. Fluorine directly realizes with krypton, xenon and radon, forming the corresponding fluorides (for example, XeF 4 , XeF 6 , KrF 2). Oxyfluoride and xenon are also known.

The interaction of fluorine with sulfur is accompanied by heat release and leads to the formation of numerous sulfur fluorides. Selenium and tellurium form higher fluorides SeF 6 and TeF 6 . Fluorine with hydrogen react with ignition; this produces hydrogen fluoride. Fluorine reacts with nitrogen only in an electric discharge. Charcoal when interacting with fluorine, it ignites at ordinary temperature; graphite reacts with it at strong heating, while the formation of solid graphite fluoride or gaseous perfluorocarbons CF 4 and C 2 F 6 is possible. With bromine, silicon, phosphorus, arsenic, fluorine interacts in the cold, forming the corresponding fluorides.

Fluorine combines vigorously with most metals; alkali and alkaline earth metals ignite in an atmosphere of fluorine in the cold, Bi, Sn, Ti, Mo, W - with slight heating. Hg, Pb, U, V react with fluorine at room temperature, Pt - at a temperature of dark red heat. When metals interact with fluorine, as a rule, higher fluorides are formed, for example, UF 6 , MoF 6 , HgF 2 . Some metals (Fe, Cu, Al, Ni, Mg, Zn) react with fluorine to form protective film fluorides, preventing further reaction.

When fluorine interacts with metal oxides in the cold, metal fluorides and oxygen are formed; the formation of metal oxyfluorides (eg MoO 2 F 2) is also possible. Non-metal oxides either add fluorine, for example SO 2 + F 2 \u003d SO 2 F 2, or oxygen in them is replaced by fluorine, for example SiO 2 + 2F 2 \u003d SiF 4 + O 2. Glass reacts very slowly with fluorine; in the presence of water, the reaction proceeds rapidly. Water interacts with fluorine: 2H 2 O + 2F 2 \u003d 4HF + O 2; in this case, OF 2 and hydrogen peroxide H 2 O 2 are also formed. Nitrogen oxides NO and NO 2 easily add fluorine to form, respectively, nitrosyl fluoride FNO and nitrile fluoride FNO 2 . Carbon monoxide adds fluorine when heated to form carbonyl fluoride: CO + F 2 = COF 2.

Metal hydroxides react with fluorine to form metal fluoride and oxygen, for example 2Ва(ОН) 2 + 2F 2 = 2ВаF 2 + 2Н 2 О + О 2 . Aqueous solutions of NaOH and KOH react with fluorine at O ​​° C to form OF 2 .

Halides of metals or non-metals interact with fluorine in the cold, and fluorine will mix all the halogens.

Sulfides, nitrides and carbides are easily fluorinated. Metal hydrides form metal fluoride and HF with fluorine in the cold; ammonia (in vapor) - N 2 and HF. Fluorine replaces hydrogen in acids or metals in their salts, for example HNO 3 (or NaNO 3) + F 2 FNO 3 + HF (or NaF); under more severe conditions, fluorine displaces oxygen from these compounds, forming sulfuryl fluoride. Alkali and alkaline earth metal carbonates react with fluorine at ordinary temperatures; this yields the corresponding fluoride, CO 2 and O 2 .

The halogens are located to the left of the noble gases in the periodic table. These five toxic non-metallic elements are in group 7 of the periodic table. These include fluorine, chlorine, bromine, iodine and astatine. Although astatine is radioactive and has only short-lived isotopes, it behaves like iodine and is often classified as a halogen. Because the halogen elements have seven valence electrons, they only need one extra electron to form a full octet. This characteristic makes them more active than other groups of non-metals.

general characteristics

Halogens form diatomic molecules (of the form X 2, where X denotes a halogen atom) - a stable form of the existence of halogens in the form of free elements. The bonds of these diatomic molecules are non-polar, covalent and single. allow them to combine easily with most elements, so they never occur uncombined in nature. Fluorine is the most active halogen, while astatine is the least.

All halogens form group I salts with similar properties. In these compounds, halogens are present in the form of halide anions with a charge of -1 (for example, Cl - , Br -). The ending -id indicates the presence of halide anions; for example Cl - is called "chloride".

In addition, the chemical properties of halogens allow them to act as oxidizing agents - to oxidize metals. Majority chemical reactions, in which halogens participate - redox in aqueous solution. Halogens form single bonds with carbon or nitrogen at where their oxidation state (CO) is -1. When a halogen atom is replaced by a covalently bonded hydrogen atom in organic compound, the prefix halo- can be used in a general sense, or the prefixes fluoro-, chlorine-, bromine-, iodine-- for specific halogens. Halogen elements can be cross-linked to form diatomic molecules with polar covalent single bonds.

Chlorine (Cl 2) was the first halogen discovered in 1774, followed by iodine (I 2), bromine (Br 2), fluorine (F 2) and astatine (At, discovered last, in 1940). The name "halogen" comes from the Greek roots hal- ("salt") and -gen ("to form"). Together, these words mean "salt-forming", emphasizing the fact that halogens react with metals to form salts. Halite is the name rock salt, a natural mineral composed of sodium chloride (NaCl). And finally, halogens are used in everyday life - fluoride is found in toothpaste, chlorine disinfects drinking water, and iodine promotes the production of thyroid hormones.

Chemical elements

Fluorine is an element with atomic number 9, denoted by the symbol F. Elemental fluorine was first discovered in 1886 by isolating it from hydrofluoric acid. In its free state, fluorine exists as a diatomic molecule (F2) and is the most abundant halogen in the earth's crust. Fluorine is the most electronegative element on the periodic table. At room temperature, it is a pale yellow gas. Fluorine also has a relatively small atomic radius. Its CO is -1, except for the elemental diatomic state, in which its oxidation state is zero. Fluorine is extremely reactive and interacts directly with all elements except helium (He), neon (Ne), and argon (Ar). In H 2 O solution, hydrofluoric acid (HF) is a weak acid. Although fluorine is strongly electronegative, its electronegativity does not determine acidity; HF is a weak acid due to the fact that the fluorine ion is basic (pH > 7). In addition, fluorine produces very powerful oxidizers. For example, fluorine can react with the inert gas xenon to form a strong oxidizing agent, xenon difluoride (XeF 2 ). Fluorine has many uses.

Chlorine is an element with atomic number 17 and chemical symbol Cl. Discovered in 1774 by isolating it from hydrochloric acid. In its elemental state, it forms a diatomic Cl 2 molecule. Chlorine has several COs: -1, +1, 3, 5 and 7. At room temperature, it is a light green gas. Since the bond that forms between two chlorine atoms is weak, the Cl 2 molecule has a very high ability to enter into compounds. Chlorine reacts with metals to form salts called chlorides. Chlorine ions are the most common ions found in sea water. Chlorine also has two isotopes: 35 Cl and 37 Cl. Sodium chloride is the most common compound of all chlorides.

Bromine - chemical element with atomic number 35 and symbol Br. It was first discovered in 1826. In its elemental form, bromine is a diatomic molecule Br 2 . At room temperature, it is a reddish-brown liquid. Its CO is -1, +1, 3, 4 and 5. Bromine is more active than iodine, but less active than chlorine. In addition, bromine has two isotopes: 79 Br and 81 Br. Bromine is found in bromide dissolved in sea water. Behind last years World bromide production has increased significantly due to its availability and long pot life. Like other halogens, bromine is an oxidizing agent and is highly toxic.

Iodine is a chemical element with atomic number 53 and symbol I. Iodine has oxidation states: -1, +1, +5 and +7. Exists as a diatomic molecule, I 2 . At room temperature it is a solid purple. Iodine has one stable isotope, 127 I. It was first discovered in 1811 using seaweed and sulfuric acid. Currently, iodine ions can be isolated in sea water. Although iodine is not very soluble in water, its solubility can be increased by using separate iodides. Yod is playing important role in the body, participating in the production of thyroid hormones.

Astatine is a radioactive element with atomic number 85 and symbol At. Its possible oxidation states are -1, +1, 3, 5, and 7. The only halogen that is not a diatomic molecule. Under normal conditions, it is a black metallic solid. Astatine is a very rare element, so little is known about it. In addition, astatine has a very short half-life, no longer than a few hours. Received in 1940 as a result of synthesis. It is believed that astatine is similar to iodine. Is different

The table below shows the structure of halogen atoms, the structure of the outer layer of electrons.

The similar structure of the outer layer of electrons determines that the physical and chemical properties of halogens are similar. However, when comparing these elements, differences are also observed.

Periodic properties in the halogen group

Physical properties simple substances halogens change with increasing element atomic number. For better assimilation and greater clarity, we offer you several tables.

The melting and boiling points of a group increase as the size of the molecule (F

Table 1. Halogens. Physical properties: melting and boiling points

• The atomic radius increases.

The kernel size increases (F< Cl < Br < I < At), так как увеличивается число протонов и нейтронов. Кроме того, с каждым периодом добавляется всё больше уровней энергии. Это приводит к большей орбитали, и, следовательно, к увеличению радиуса атома.

Table 2. Halogens. Physical properties: atomic radii

• The ionization energy decreases.

If the outer valence electrons are not near the nucleus, then it will not take much energy to remove them from it. Thus, the energy required to push the outer electron out is not as high at the bottom of the element group, as there are more energy levels. In addition, the high ionization energy causes the element to exhibit non-metallic qualities. Iodine and astatine display exhibit metallic properties because the ionization energy is reduced (At< I < Br < Cl < F).

Table 3. Halogens. Physical properties: ionization energy

• The electronegativity decreases.

The number of valence electrons in an atom increases with increasing energy levels at progressively lower levels. The electrons are progressively further away from the nucleus; Thus, the nucleus and electrons are not both attracted to each other. An increase in shielding is observed. Therefore, the electronegativity decreases with increasing period (At< I < Br < Cl < F).

Table 4. Halogens. Physical properties: electronegativity

• The electron affinity decreases.

Since the size of an atom increases with increasing period, electron affinity tends to decrease (B< I < Br < F < Cl). Исключение - фтор, сродство которого меньше, чем у хлора. Это можно объяснить меньшим размером фтора по сравнению с хлором.

Table 5. Electron affinity of halogens

• The reactivity of the elements decreases.

The reactivity of halogens decreases with increasing period (At

Hydrogen + halogens

A halide is formed when a halogen reacts with another, less electronegative element to form a binary compound. Hydrogen reacts with halogens to form HX halides:

• hydrogen fluoride HF;
• hydrogen chloride HCl;
• hydrogen bromide HBr;
• hydrogen iodide HI.

Hydrogen halides readily dissolve in water to form hydrohalic (hydrofluoric, hydrochloric, hydrobromic, hydroiodic) acids. The properties of these acids are given below.

Acids are formed by the following reaction: HX (aq) + H 2 O (l) → X - (aq) + H 3 O + (aq).

All hydrogen halides form strong acids, with the exception of HF.

The acidity of hydrohalic acids increases: HF

Hydrofluoric acid is able to engrave glass and some inorganic fluorides for a long time.

It may seem counterintuitive that HF ​​is the weakest hydrohalic acid, since fluorine has the highest electronegativity. However, the H-F bond is very strong, resulting in a very weak acid. A strong bond is determined by a short bond length and a high dissociation energy. Of all the hydrogen halides, HF has the shortest bond length and the largest bond dissociation energy.

Halogen oxo acids

Halogen oxo acids are acids with hydrogen, oxygen and halogen atoms. Their acidity can be determined using structure analysis. Halogen oxoacids are listed below:

• Hypochlorous acid HOCl.
• Chloric acid HClO 2 .
• Perchloric acid HClO 3 .
• Perchloric acid HClO 4 .
• hypobromous acid HOBr.
• Bromic acid HBrO 3 .
• Bromic acid HBrO 4 .
• Iodous acid HOI.
• Iodic acid HIO 3 .
• Metaiodic acid HIO4, H5IO6.

In each of these acids, a proton is bonded to an oxygen atom, so comparing proton bond lengths is useless here. Electronegativity plays a dominant role here. The activity of the acid increases with the increase in the number of oxygen atoms associated with the central atom.

Appearance and state of matter

The main physical properties of halogens can be summarized in the following table.

Appearance explanation

The color of halogens is the result of the absorption of visible light by molecules, which causes the excitation of electrons. Fluorine absorbs violet light and therefore appears light yellow. Iodine, on the other hand, absorbs yellow light and appears purple (yellow and purple are complementary colors). The color of halogens becomes darker as the period increases.

In closed containers, liquid bromine and solid iodine are in equilibrium with their vapors, which can be observed as a colored gas.

Although the color of astatine is unknown, it is assumed that it must be darker than iodine (i.e. black) in accordance with the observed pattern.

Now, if you are asked: "Characterize the physical properties of halogens," you will have something to say.

The oxidation state of halogens in compounds

The oxidation state is often used instead of the concept of "halogen valency". As a rule, the oxidation state is -1. But if the halogen is bonded to oxygen or another halogen, it can take on other states: the CO of oxygen-2 takes precedence. In the case of two different halogen atoms bonded together, the more electronegative atom prevails and accepts CO-1.

For example, in iodine chloride (ICl), chlorine has CO -1, and iodine +1. Chlorine is more electronegative than iodine, so its CO is -1.

In bromic acid (HBrO 4), oxygen has CO -8 (-2 x 4 atoms = -8). Hydrogen has an overall oxidation state of +1. Adding these values ​​gives CO -7. Since the final CO of the compound must be zero, the CO of bromine is +7.

The third exception to the rule is the oxidation state of halogen in elemental form (X 2), where its CO is zero.

Why is the SD of fluorine always -1?

Electronegativity increases with increasing period. Therefore, fluorine has the highest electronegativity of all the elements, as evidenced by its position in the periodic table. Its electronic configuration is 1s 2 2s 2 2p 5 . If fluorine gains one more electron, the outermost p-orbitals are completely filled and make up a full octet. Because fluorine has a high electronegativity, it can easily steal an electron from a nearby atom. Fluorine in this case is isoelectronic to the inert gas (with eight valence electrons), all of its outer orbitals are filled. In this state, fluorine is much more stable.

Production and use of halogens

In nature, halogens are in the state of anions, so free halogens are obtained by oxidation by electrolysis or using oxidizing agents. For example, chlorine is produced by the hydrolysis of a salt solution. The use of halogens and their compounds is diverse.

• Fluorine. Although fluorine is highly reactive, it is used in many industrial applications. For example, it is a key component of polytetrafluoroethylene (Teflon) and some other fluoropolymers. CFCs are organics that were previously used as refrigerants and propellants in aerosols. Their use has ceased due to their possible impact on the environment. They have been replaced by hydrochlorofluorocarbons. Fluoride is added to toothpaste (SnF2) and drinking water (NaF) to prevent tooth decay. This halogen is found in clay used for the production of certain types of ceramics (LiF), used in nuclear power (UF 6), for the production of the antibiotic fluoroquinolone, aluminum (Na 3 AlF 6), for the insulation of high-voltage equipment (SF 6).
• Chlorine also found various uses. It is used to disinfect drinking water and swimming pools. (NaClO) is the main ingredient in bleaches. Hydrochloric acid is widely used in industry and laboratories. Chlorine is present in polyvinyl chloride (PVC) and other polymers that are used to insulate wires, pipes, and electronics. In addition, chlorine has proven useful in the pharmaceutical industry. Medicines containing chlorine are used to treat infections, allergies, and diabetes. The neutral form of hydrochloride is a component of many drugs. Chlorine is also used to sterilize hospital equipment and disinfect. In agriculture, chlorine is an ingredient in many commercial pesticides: DDT (dichlorodiphenyltrichloroethane) was used as an agricultural insecticide, but its use has been discontinued.

• Bromine, due to its incombustibility, is used to suppress combustion. It is also found in methyl bromide, a pesticide used to preserve crops and suppress bacteria. However, overuse has been phased out due to its effects on the ozone layer. Bromine is used in the production of gasoline, photographic film, fire extinguishers, medicines for the treatment of pneumonia and Alzheimer's disease.
• Iodine plays an important role in the proper functioning of the thyroid gland. If the body does not get enough iodine, the thyroid gland enlarges. To prevent goiter, this halogen is added to table salt. Iodine is also used as an antiseptic. Iodine is found in solutions used to clean open wounds, as well as in disinfectant sprays. In addition, silver iodide is essential in photography.
• Astatine- a radioactive and rare earth halogen, therefore it is not used anywhere else. However, it is believed that this element may assist iodine in the regulation of thyroid hormones.