IOD(iodine) (Latin Iodum), I (read “iodine”), chemical element with atomic number 53, atomic mass 126.9045.
Iodine is located in the fifth period in group VIIA of Mendeleev’s periodic table of elements and belongs to the halogens.
Natural iodine consists of only one nuclide, iodine-127. The configuration of the outer electron layer is 5s 2 p 5. In compounds it exhibits oxidation states 1, +1, +3, +5 and +7 (valences I, III, V and VII).
The radius of the neutral iodine atom is 0.136 nm, the ionic radii of I , I 5+ and I 7+ are, respectively, 0.206; 0.058-0.109; 0.056-0.067 nm. The energies of sequential ionization of a neutral iodine atom are, respectively, 10.45; 19.10; 33 eV. Electron affinity 3.08 eV. According to the Pauling scale, the electronegativity of iodine is 2.66, iodine is a non-metal.
Under normal conditions, iodine is a solid black-gray substance with a metallic luster and a specific odor.
Physical and chemical properties: The crystal lattice of iodine is rhombic, the unit cell parameters are a = 0.4792 nm, b = 0.7271 nm, c = 0.9803 nm. Melting point 113.5°C, boiling point 184.35°C. An important feature of iodine is its ability to sublimate (transition from solid to vapor state) already at room temperature. The density of iodine is 4.930 kg/cm3. The standard electrode potential I 2 /I in an aqueous solution is +0.535 V.
In vapors, in melts and in crystals, it exists in the form of diatomic molecules I 2 . Bond length 0.266 nm, bond energy 148.8 kJ/mol. The degree of dissociation of molecules into atoms at 727°C 2.8%, at 1727°C 89.5%.
Iodine is poorly soluble in water, and a reversible reaction occurs
I 2 + H 2 O = HI + HIO
Iodine is highly soluble in most organic solvents (carbon disulfide, hydrocarbons, CCl 4, CHCl 3, benzene, alcohols, diethyl ether and others). The solubility of iodine in water increases if there are iodide ions I in the water, since I 2 molecules form complex ions I 3 with iodide ions.
In terms of reactivity, iodine is the least active halogen. Among non-metals, it reacts directly without heating only with phosphorus (P) (forming PI 3) and arsenic (As) (forming AsI 3), as well as with other halogens. Thus, iodine reacts with bromine (Br) practically without heating, and a compound of the composition IBr is formed. When heated, it reacts with hydrogen (H) H 2 to form HI gas.
Metals react with iodine usually when heated. The reaction is facilitated by the presence of water vapor or the addition of liquid water. Thus, aluminum (Al) powder reacts with iodine if a drop of water is added to the powder:
2Al + 3I 2 = 2AlI 3.
It is interesting that iodine forms compounds with many metals not in the highest oxidation state of the metal atom, but in the lowest. Thus, with copper (Cu) iodine forms only a compound of composition CuI, with iron (Fe) composition FeI 2. All metal iodides, except iodides AgI, CuI and Hg 2 I 2, are highly soluble in water.
Iodine reacts with an aqueous solution of alkali, for example:
3I 2 + 6NaOH = 5NaI + NaIO 3 + 3H 2 O,
and also with a solution of soda:
3I 2 + 3Na 2 CO 3 = 5NaI + NaIO 3 + 3CO 2
Application: iodine is used to produce high-purity titanium (Ti), zirconium (Zr), hafnium (Hf), niobium (Nb) and other metals (the so-called iodide refining of metals). During iodide refining, the original metal with impurities is converted into the form of volatile iodides, and then the resulting iodides are decomposed on a hot thin thread. The thread is made of pre-cleaned metal, which is subjected to refining. Its temperature is selected such that only the iodide of the metal being purified can decompose on the filament, while the remaining iodides remain in the vapor phase.
Iodine is also used in incandescent iodine lamps, which have a tungsten filament and are characterized by a long service life. As a rule, in such lamps, iodine vapor is in an environment of the heavy inert gas xenon (Xe) (lamps are often called xenon) and reacts with tungsten atoms (W) evaporating from the heated coil. Iodide, which is volatile under these conditions, is formed, which sooner or later ends up again near the helix. Immediate decomposition of the iodide occurs, and the released tungsten (W) again appears on the spiral. Iodine is also used in food additives, dyes, catalysts, photography, and analytical chemistry.
Biological role: Iodine is a trace element and is present in all living organisms. Its content in plants depends on the presence of its compounds in soil and water. Some seaweeds (seaweed, or kelp, fucus and others) accumulate up to 1% iodine. Iodine is included in the skeletal protein of sonchin sponges and the skeletal proteins of marine polychaete worms. In animals and humans, iodine is part of the thyroid hormones thyroxine and triiodothyronine, which have a multifaceted effect on the growth, development and metabolism of the body (especially on the intensity of basal metabolism, oxidative processes, heat production). The body of an average person (body weight 70 kg) contains 12-20 mg of iodine, the daily requirement is about 0.2 mg.
Iodine in medicine: In medicine, “iodine tincture” is used, which has a disinfectant effect. It should be borne in mind that only small wounds can be treated with iodine tincture, since iodine can cause tissue necrosis, which, for large wounds, will increase their healing time. Micro amounts of iodine are vital for humans; iodine deficiency in the body leads to thyroid disease - endemic goiter, which occurs in areas with low iodine content in the air, soil, and waters. Usually these are highlands and areas far from the sea. In order to ensure that the body receives the necessary amounts of iodine, iodized table salt is used.
Artificial iodine radionuclides - iodine-125, iodine-131, iodine-132 and others - are used for the diagnosis and treatment of thyroid diseases. However, excessive accumulation of iodine-131 radionuclide in the thyroid gland (which, in particular, became possible after the accident at the Chernobyl nuclear power plant) can lead to cancer. To prevent the accumulation of iodine-131 in the thyroid gland, a little regular (stable) iodine is injected into the body. The thyroid gland, having absorbed this iodine, becomes saturated with it and is no longer able to capture the radionuclide iodine-131. So even if iodine-131 then enters the body, it will be quickly removed from it (the half-life of iodine-131 is relatively short and is about 8 days, so the decrease in radioactivity also occurs due to its decay). In order to completely “block” the thyroid gland from accumulating iodine-131 in it, doctors recommend drinking a glass of milk once a week, to which one drop of iodine tincture has been added. It should be remembered that iodine is toxic both in the form of I 2 and in the form of iodides.
Everyone has ever used an alcohol solution of iodine; some are familiar with it from chemistry lessons. Some people have experienced a lack of iodine in the body, while others confuse it with brilliant green. In this article we have collected answers to the most frequently asked questions about iodine, we hope it will be useful!
When and by whom was iodine discovered?
The chemical element “Iodine” was added to the periodic table in 1871.Like many chemical elements, iodine was discovered by accident in 1811 by the Frenchman Bernard Courtois while preparing saltpeter from seaweed. As a chemical element, the substance received the name “iodine” two years later, and was officially included in the periodic table in 1871.
Where and how is iodine obtained?
In its pure form (free form), iodine is extremely rare - mainly in Japan and Chile. The main production is made from seaweed (5 kg is obtained from 1 ton of dry kelp), sea water (up to 30 mg from a ton of water) or from oil drilling waters (up to 70 mg from a ton of water). There is a method for obtaining technical iodine from waste from the production of saltpeter and ash, but the content of the substance in the starting materials is no more than 0.4%.
The method of obtaining iodine has two directions.
- Seaweed ash is mixed with concentrated sulfuric acid and heated. After evaporation of moisture, iodine is obtained.
- Iodine in liquids (sea or lake salt water, oil water) is bound with starch, or silver and copper salts, or kerosene (an outdated method, as it is expensive) into insoluble compounds, and then the water is evaporated. Later they began to use the carbon method for extracting iodine.
How does iodine affect the human body?
Iodine and its derivatives are part of hormones that affect the metabolism of the human body, its growth and development, so the average person needs to consume up to 0.15 mg of iodine daily. The absence of iodine or its deficiency in the diet leads to diseases of the thyroid gland and the development of endemic goiter, hypothyroidism and cretinism.
An indicator of iodine deficiency in the body is fatigue and depressed mood, headache and so-called “natural laziness”, irritability and nervousness, weakening of memory and intelligence. Arrhythmia, high blood pressure and a drop in hemoglobin levels in the blood appear. Very toxic - 3 g of the substance is a lethal dose for any living organism.
In large quantities it causes damage to the cardiovascular system, kidneys and pulmonary edema; cough and runny nose, lacrimation and pain in the eyes (if it comes into contact with the mucous membrane); general weakness and fever, vomiting and diarrhea, increased heart rate and heart pain.
How to replenish iodine in the body?
- The main source of natural iodine is seafood, but it is obtained as far from the coast as possible: in coastal areas, iodine is washed out of the soil, and its content in products is insignificant. Eat seafood - this can restore the substance content in the body to a certain extent.
- You can artificially add iodine to table salt, eat foods containing this microelement - sunflower oil, food additives.
- Pharmacies sell tablets with a high iodine content - relatively harmless drugs (for example, iodine-active, antistrumin).
- A lot of iodine is found in persimmons and walnuts.
Where is iodine found?
Iodine is present almost everywhere. The highest iodine content is in products of marine origin, in sea water itself and in salty lake water.
In free form - as a mineral - iodine is present in thermal springs of volcanoes and natural iodides (lautarite, iodobromite, embolite, mayersite). It is found in oil drilling waters, sodium nitrate solutions, lyes from saltpeter and potassium production.
What foods contain iodine?
In seafood: fish (cod and halibut) and fish oil, crustaceans and shellfish (scallops, crabs, shrimp, squid, oysters, mussels), seaweed. This is followed by dairy products and chicken eggs, feijoa and persimmons, sweet peppers, peels and kernels of walnuts, black grapes, grain crops (buckwheat, corn, wheat, millet), river fish and red beans. Iodine is found in orange and red colored juices.
There is even less iodine in soy products (milk, sauce, tofu), onions, garlic, beets, potatoes, carrots, beans, strawberries (about 40-100 times less than in seaweed), but it is there.
What foods do not contain iodine?
Iodine is not found in baked goods (homemade) that use regular salt without iodine, peeled potatoes, unsalted vegetables (raw and frozen), peanuts, almonds and egg whites. There is practically no iodine in cereals that are poor in natural salts; macaroni, cocoa powder, white raisins and dark chocolate. This applies to vegetable oils, including soybean oil.
Almost all known seasonings in dried form (black pepper, herbs) also do not have iodine-containing components - iodine quickly decomposes (evaporates) in the open air, which is why iodized salt is suitable for use for only 2 months (if the pack is open).
Carbonated drinks - Coca Cola and its derivatives, wine, black coffee, beer, lemonade - all this also does not contain iodine.
Linen fabrics:
Option 1. Cover the stain with baking soda, pour vinegar on top and leave for 12 hours, and then wash in warm, clean water.
Option 2. Dissolve a teaspoon of ammonia in 0.5 liters of water, and wipe the stain with the resulting solution. Next, wash in warm soapy water.
Option 3. Make a thick paste of starch in water, apply it to the stain and wait for the stain to turn blue. If necessary, repeat again and wash the product in warm soapy water.
Option 4. Rub the stain with raw potatoes and wash the product in warm soapy water.
Option 5. You can wipe the stain with liquid ascorbic acid (or dissolve the tablet in water), and then wash it in soap and water.
Wool, cotton and silk fabrics:
The stain should be wiped with a hyposulfite solution (a teaspoon per glass of water) and washed in warm water. You can wipe the stain with ammonia and wash it in the usual way.
How to wash iodine from skin
There are several options:
- Olive oil or fatty cream is applied to the skin to absorb iodine. After an hour, the iodine is washed off with a body sponge and soap.
- Take a bath with sea salt, and at the end use a washcloth and baby soap (laundry soap as a last resort).
- For delicate skin, you can use a scrub instead of a washcloth, and massage the area with the stain. After this, you can lubricate the skin with nourishing cream or milk.
- You can apply cotton wool with alcohol, moonshine or vodka to the stain for 5 minutes, and then rub. The procedure can be repeated several times.
- Removes iodine stains by hand washing items or a regular bath with powder or lemon juice.
How to gargle with iodine
The method is quite simple - you need to add a few drops of iodine to a glass of warm water until you get a light brown solution. But the effect will be better and stronger if you add a teaspoon of soda and table salt to the water. The method has proven itself in the treatment of purulent tonsillitis and chronic tonsillitis. The procedure can be repeated 3-4 times a day (for purulent sore throat - every 4 hours) for 4 days.
If you have a sore throat, you should not lubricate your throat with an alcohol solution of iodine, such as, for example, Iodinol. Otherwise, you will simply burn the mucous membrane.
How to make an iodine grid, how often can you make an iodine grid
You need to take a thin stick with cotton wool, moisten it in a 5% alcohol solution of iodine and draw intersecting horizontal and vertical stripes on the skin in the form of a plate with 1x1cm squares. This is the ideal geometry for uniform distribution of iodine: it is absorbed quickly and efficiently.
It can be done only two to three times during the week for any disease.
At what age can you apply iodine?
Doctors do not recommend applying iodine to the skin even in adolescence - iodine burns the skin. But an iodine grid (one-time use) can be done from the age of five. But there is a more “advanced” and safer version of iodine that can also be used.
Why is iodine in the periodic table, but brilliant green is not?
Because brilliant green is a synthetic antiseptic, an aniline dye. The periodic table includes only chemical elements and compounds that exist in nature in their pure form.
Iodized salt should replace regular salt for people living in regions of iodine deficiency. Because this salt helps restore balance in case of iodine deficiency in the human body, it is a prevention of iodine deficiency diseases in children, pregnant and lactating women, and adolescents. Salt with iodine helps prevent the thyroid gland from absorbing radioactive iodine components and is a protection against radiation, inflammatory processes and diseases.
How to make iodized salt
Iodine is added to sea or lake salt water in a certain concentration, mixed with water and only then evaporated.
Iodine– is included in the periodic table of Mendeleev and belongs to the group of halogens. It would be correct to call the element iodine from the Latin word Iodum. It consists of black-gray crystals with a violet metallic sheen (see photo). By the way, the ancient Greek name of the element is translated as “violet-like.” Iodine vapor has a pungent odor and purple color.
Iodine was obtained in 1811 by the chemist and industrialist Courtois from seaweed by heating in concentrated sulfuric acid. A few years later, the famous Gay-Lussac investigated the chemical properties of the element.
Iodine is very scattered in nature and due to this it is present almost anywhere on our planet. In free form in the form of minerals, this is a very rare substance; deposits are mainly developed in Japan and Chile. It is also obtained industrially from oil drilling waters, seaweed, and saltpeter.
The iodine molecule is chemically very active and is a strong oxidizing agent.
A large mass of iodine is contained in sea water - during geological processes, iodine was gradually washed away from the surface of the earth's crust under the influence of ice, snow, rain and carried away by rivers to the seas. A lot of it is found in chernozem soils and peat bogs. But mountainous areas, on the contrary, are very depleted in iodine, again due to the large amount of precipitation.
The action of iodine and its biological role
The action of a macronutrient is vital for a living organism. Iodine enters the human blood with food and almost the entire amount is absorbed in the small intestine, from where it penetrates the blood and the thyroid gland. It is also possible for a certain amount to enter with inhaled air and through the skin.
Iodine belongs to the biotic elements, i.e. to those affecting life activity:
- The thyroid gland accelerates metabolism, iodine supplies the blood, through reactions in the gland, with the necessary organic compounds and hormones that affect the level of metabolic intensity, oxidation processes and heat production.
- Nervous system – thanks to the action of the element, the growth of healthy cells of the nervous system is enhanced, due to which excessive irritability disappears and the emotional background becomes stable.
- Child development and growth - in the presence of iodine, protein synthesis occurs and metabolic processes in muscle tissue are accelerated, which leads to increased physical endurance, and it also has a positive effect on mental abilities.
- Lipid metabolism - a macroelement that stimulates metabolism in the subcutaneous fat layer, and thus fights obesity and its unpleasant manifestation - cellulite.
- Carbohydrate metabolism - through the work of the thyroid gland, iodine has an effect on the absorption of carbohydrates by the intestines.
- Persistent immunity - consuming the element allows the body to actively resist colds and viral diseases.
Iodine also promotes the formation of phagocytes - cells in the blood that destroy harmful microorganisms. But the thyroid gland, in which it accumulates, is involved in all the actions of iodine. It is by passing through it that pathogenic organisms lose their strength.
Medicine associates the main biological significance of iodine as a macronutrient with endemic goiter, which occurs due to iodine deficiency. This disease occurs mainly in mountainous regions of all continents. It is promoted by a lack of cobalt and an excess of manganese, as well as an unbalanced diet, when there is an excess of carbohydrates and fats with a lack of proteins and vitamins. Treatment among the population will only make sense with an integrated approach. It is necessary to carry out prevention in combination with optimizing the composition of the environment and improving sanitary and hygienic living and working conditions.
Iodine in the history of medicine
Thousands of years before the scientific discovery of the element, people learned to use it correctly. Here are some facts from history:
- already 5 thousand years ago in China, goiter was cured with the help of seaweed, and later recipes for treatment with extracts from the thyroid glands of animals (deer and pigs) were described;
- Around the same time, the Sumerians were looking for a magical herb in the northern coastal regions, the description of which was lost, and later information appeared about the treatment of goiter with kelp or seaweed, and this was done at the state level;
- about 3,000 years ago, the same Chinese discovered that the disease appeared more often in areas with mountainous terrain and poor drinking water quality, the Romans discovered this fact a thousand years later;
- In Europe, the earliest artistic depiction of a goiter is dated 1215, while among the Indians it is dated to the third millennium BC. The paintings show a man with a goiter on his neck and a rattle called a "fool's scepter", which was an indication of dementia;
- in the Renaissance, a goiter was considered an attribute of beauty, which may have been a consequence of that same dementia among the “fashion” setters;
- The first mention of the term "thyroid gland" was used by the Englishman Thomas Warton in the mid-17th century, and the word "cretin" was used in 1754 in Diderot's Encyclopedia.
As you can see, the connection between goiter and a decrease in the level of mental abilities was discovered relatively recently. It was only in the mid-18th century that Denis Diderot described the word “cretin” as weak-minded, deaf, ugly and with a goiter up to the waist. And Napoleon drew attention to the fact that the presence of this disease in recruits initially makes them unfit for service. This theory was scientifically confirmed in 1896 by biochemist E. Bauman.
Daily value (need for an adult, for children, as well as for pregnant women)
The daily norm of a macronutrient depends on the body and age of the person. For example, for an adult the norm is about 150-300 mcg. School-age children need about 120 mcg per day, and preschool children need 50-90 mcg.
It is quite simple to determine the norm from the calculation that our body requires 2-4 mcg/1 kg of body weight. It is worth considering that not all iodine accumulates in organs and tissues; excess is excreted in urine and saliva. That is, the iron will take exactly the amount it needs. This is good only in the case of a healthy, functioning organ. If there are disturbances in the functioning of the thyroid gland, then a medical adjustment of the daily norm is necessary.
Pregnant women and women during breastfeeding, children and adolescents need an increased dose of the element. But it is imperative to obtain a recommendation from your attending physician.
It has been noted that in the post-Soviet space the situation is close to catastrophic. Because actual iodine consumption is about 50-80 mcg, which is three times less than required.
Interesting fact: depending on the changing seasons, the level of iodine concentration in the blood also changes. In autumn it begins to decline, and starting in March it rises until it reaches a maximum in June. The amplitude of the oscillations is insignificant, but has not yet been explained by science.
Lack (deficiency) of iodine in the body - what are the symptoms?
Lack of the macronutrient iodine, according to statistics, is widespread throughout the planet, and about a third of the entire population is at risk of iodine deficiency.
Iodine is found in the main thyroid hormones (about 60-65%), which, in turn, take part in metabolic processes and affect:
- mental development;
- growth of bone tissue;
- protein synthesis;
- breakdown of cholesterol and fats;
- stimulation of myelogenesis.
Iodine deficiency can lead to problems during pregnancy: congenital genetic abnormalities, stillbirth, cretinism. Therefore, it is necessary to monitor iodine levels throughout a person’s life. If it is deficient, the child may be born with increased body weight and jaundice, which leads to swelling and delayed healing of the umbilical remnant. The hairline is very weakened and is often affected by seborrhea. There may be a delay in the eruption of baby teeth, and subsequently permanent teeth. Deformation of the limbs occurs. When listening to the heart, functional murmurs are heard. Intestinal dysfunction occurs. Such babies may begin to sit and walk late.
Iodine deficiency can be fraught with mental retardation even at an older age; memory, motor skills, and perception suffer; they often suffer from colds, as a result of which it is difficult for them to concentrate and their academic performance declines. There may also be a violation of physical, sexual and neuropsychiatric development.
It is possible to achieve results in correcting iodine deficiency only by starting complex therapy from birth and continuing prevention throughout life. This is usually due to the fact that iodine is not able to accumulate in the body and comes exclusively from food. And its presence in the body is vital, so negligence is unacceptable.
For an infant, the source of the element is breast milk, but only if the mother takes the required amount. When artificial feeding, the dosage must be carefully maintained.
Chronic deficiency is obvious in the truest sense of the word. Externally, it is expressed in an enlargement of the thyroid gland (endemic gland). This disease is also called Graves' disease. Its essence lies in the fact that in case of iodine deficiency, iron increases in size to avoid insufficient production of hormones. Thyrotoxicosis develops (lack of those same hormones), the symptoms of which are increased heartbeat, nervousness, weight loss, sweating, restless sleep.
Also, the influence of an insufficient amount of the element affects the general condition of the body and a person’s appearance: weakness, drowsiness, hearing and memory impairment, pale and dry skin, hair problems, shortness of breath.
A folk remedy for checking iodine deficiency is applying a grid with an alcohol solution to the skin. If it quickly disappears, then measures need to be taken, but if the drawing does not disappear within 24 hours, then everything is in order with the presence of the element, although you should not stop there and continue prevention. But doctors do not trust this method and use urine or blood tests. They believe that when applied to the skin, iodine can only have an irritating effect, causing blood outflow and dilation of skin capillaries.
Today, iodine deficiency is the most common disease spread by non-infectious means, which leads to mental retardation of the entire nation. This disease is becoming an “epidemic” and control in particularly affected countries must take place at the legislative level.
According to WHO statistics, about 200 million people are considered affected and almost a billion are at risk.
Signs of excess iodine and iodine poisoning
Excess iodine in the body can still exist, despite a global deficiency of the element as a whole. It may be caused by a violation of iodine metabolism and its excessive intake. An excess of this chemical can cause poisoning, because high concentrations have a toxic effect. Employees of enterprises with increased harmfulness are exposed to such poisoning, where iodine is released in the form of steam.
The toxic effect of the element can lead to disruption of the general condition of the body (muscle weakness, sweating, diarrhea and weight loss), and with chronic action, painful sensations in the stomach, vomiting, lacrimation, tinnitus, and dizziness may appear. Depigmentation of the skin and hair occurs, which causes premature graying.
What food sources does it contain?
Iodine consumption occurs mainly in foods of plant and animal origin. But it is worth considering that the content of the element is determined by the condition of the soil on which they are grown. The most saturated areas are located in areas close to the seas or oceans, and the poorest are in mountainous areas due to leaching from the soil by precipitation. And it has been noticed that city residents suffer less from shortages than rural residents. The reason for this is the consumption by city residents of a wide range of imported products.
In addition to iodine-rich seafood (seaweed, fish, shrimp, etc.), you should eat radishes, carrots, tomatoes, potatoes, cabbage, currants, strawberries, eggs, and onions. The element is also found in milk, beans, meat and buckwheat.
But consuming soy products doubles the need for macronutrients, because they (the products) cause an increase in the volume of the thyroid gland.
High-quality seafood is very expensive, so to replenish the iodine balance in the body, you have to limit yourself to consuming sea salt. But at the same time, many do not take into account the fact that during the heat treatment of a given product, the previously indicated chemical element practically does not remain in it. When using a special salt saturated with iodine, the value is short-lived, for the reason that the element “evaporates” from an open pack due to the volatile properties of this substance. Although such salt in our conditions is the most effective and cheapest remedy. However, it is necessary to add it to food only before consumption, and not during the cooking process.
An alcohol solution of iodine cannot be used to replenish iodine deficiency, because it is suitable for external use only and contains high concentrations that can cause poisoning with this substance.
Medical preparations of iodine are produced in the form of sodium and potassium salts, Lugol's solution, infusions and vitamin preparations. However, they may cause some allergic reactions.
Indications for use
The indications for prescribing a macronutrient are quite extensive, but all are related to the stable functioning of the thyroid gland:
Greek – iodes (violet color). The word entered the Russian language in the second third of the 19th century. The name of this substance was coined by the French chemist Gay-Lussac. He relied on a Greek word that can be translated as “having the color of a violet.” Etymological Dictionary of Semenov
What is iodine? The molar mass of this element is 127 g/mol. Let's consider the main characteristics of this halogen and its significance for living organisms.
Introduction
Let's start with the fact that halogen was discovered at the beginning of the nineteenth century by the French chemist Courtois. Where is iodine located? The molar mass of this element was indicated above, and its atomic number is 53. It belongs to the halogens and is in the VIIA subgroup. Under natural conditions, it exists as a stable atom, and radioactive isotopes of iodine have been synthesized.
Atomic structure
Iodine, whose molar mass is 127 g/mol, does not contain seven valence electrons. In addition, it has a vacant d-orbital. In a variety of compounds it exhibits odd oxidation states. The significant molar mass of iodine, the large atomic radius, and the insignificant value of ionization energy allow such an element not only to exhibit the properties of an acceptor, but also to become an electron donor in some chemical interactions.
Physical properties
Since the molar mass of iodine is 2 - 254 g/mol, more precisely, its molecules, this substance at room temperature is a violet-black crystalline substance with a metallic luster. Its crystals are diatomic molecules formed due to the intermolecular van der Waals interaction.
Iodine, whose molar value is 254 g/mol, sublimes when heated to 183 °C, forming violet vapor. This substance is poorly soluble in water. As the temperature rises, this figure increases. Iodine, the molar mass of which is considered to be quite large, forms a complex compound in an iodide solution. Its atom has a rapidly polarized electron shell. Cations of many elements are capable of entering the electron shell of an atom, leading to its deformation. That is why the existence of a positively polarized iodine atom is allowed, color appears, and high physiological activity of iodine compounds appears.
Chemical properties
The molar mass of iodine explains its low chemical activity. It does not interact with most metals, inert gases, carbon, and nitrogen. With metals it forms iodides, which have ionic bonds.
Saturated organic substances do not interact with iodine because the C-H bond energy exceeds that between carbon and iodine.
Biological significance
Why does the human body need iodine? Molar mass and chemical properties are discussed above, now let's focus on its physiological characteristics. It is one of the most important microelements that take part in metabolic processes. The adult body contains about 30 mg of iodine, with about 10 mg located in the thyroid gland. In the body, this element is found in the form of iodides, organic compounds (thyreglobulin protein), and iodized amino acids.
The molar mass of iodine equivalent is 127, it is used when carrying out quantitative calculations.
Functional meaning
Plant foods are the main source of this element for humans. From the intestines, this halogen enters the blood and is then taken up by the thyroid gland. The kidneys are responsible for removing iodine from the body.
The thyroid gland has special enzymatic systems that convert iodine from an inactive biological form to an active state.
Features of transformations
On the outer surface of the cell membrane, it is oxidized by iodide oxidase to hypoiodite, which enters the body through the cell membrane.
Inside the cell, it is restored due to the action of the enzyme iodine reductase to iodide. It is he who is an active participant in the process of biosynthesis of thyroid hormones.
Hypotheses for the synthesis of thyroxine and triiodothyronine
Currently, there are two main versions about this transformation. According to one hypothesis, under the action of an enzyme, iodine is attached to the thyroglobulin molecule (molar mass and properties are indicated earlier).
The second version is that tyrosine is iodinated, then thyreglobulin is synthesized. It is possible that there is a stepwise biosynthesis of thyroxine. At the first stage, the tyrosine molecule is iodinated, diiodotyrosine is formed. At the second stage, their enzymatic condensation occurs with the release of alanine.
Circulating blood contains about 70 percent iodine in organic compounds, the rest is in the form of iodide ion.
For a healthy person, a low concentration of free thyroid hormones in the blood plasma is assumed. Most of the iodine-containing organic substances are represented by thyroxine, which is associated with specific plasma proteins: albumin, globulin.
Thyroid hormones, which enter tissues from blood plasma, will be released from their binding by plasma proteins; they perform a hormonal role.
More than half of the densely populated territory of our state suffers from insufficient iodine content in soil, water, and food. Therefore, the problem of iodine deficiency is particularly relevant for Russia at present. Iodine, molar mass and its characteristics are an issue that is discussed in the school chemistry course.
At first, there is a slight enlargement of the thyroid gland, but then the disease spreads to the rest of the body systems. As a result, metabolic processes are disrupted and growth slows down. In some cases, endemic goiter causes deafness and cretinism. Lethargy, weakness, fatigue, bad mood appear, and appetite decreases. Children and adolescents experience a significant decline in school performance, loss of interest in cognitive activity, and the appearance of excessive aggression.
The danger of oversupply
Iodine in its pure form is a potent poison. Vomiting begins with brown contents. Body temperature rises. There is a drop in blood pressure, and seizures may occur. It is necessary for the victim to rinse the stomach, give large quantities of starch, flour paste, and saline laxative. Take the victim to the hospital.
Drinking alcohol tincture can cause burns to the mucous membranes of the mouth, pharynx, larynx, esophagus, and stomach. If you have an allergy, any independent treatment with iodine-containing drugs is excluded!
When treating wounds and scratches with iodine, only the edges of the wound are lubricated - blood reduces the bactericidal properties of iodine, and if iodine gets on tissues that are not protected by the skin, it causes severe burns.
In what form does this element enter our body? The source may be salt, which has a molar mass of 167 g/mol. Potassium iodine is a salt that is found in dissolved form in many seafood products. That is why doctors recommend eating algae and sea fish to compensate for the lack of iodine in the body.
Conclusion
The total amount in the human body contains from twenty to thirty-five milligrams of iodine. Its distribution throughout the body is very uneven: a smaller part of iodine is concentrated in the blood and kidneys, and a large part in the thyroid gland.
If we are talking about the absolute values of the quantitative content of iodine in a living organism, then it should be noted that about half of all iodine is located in the thyroid gland (about 10-15 mg). It is called the organ in which iodine accumulates. A significant amount of this element was found in the following products: liver, hair, prostate gland, pituitary gland, bile. In muscles, the approximate concentration of halogen is a thousand times less than in the thyroid gland.
Iodine enters our body mainly through the digestive tract. Many inorganic iodine compounds are found in foods and water. They can be absorbed almost along the entire length of the gastrointestinal tract, but the process occurs more intensively in the small intestine. Also, iodine enters the body through the lungs, this is obvious for coastal marine areas. 4000 liters of air passing through a person's lungs in 12 hours contains 0.044 mg of iodine, a fifth of which is exhaled back. Small amounts of iodine are absorbed through the skin.
An excess of iodine in the human body is much less common than its deficiency. Basically, problems arise from an excess of iodine in people who are engaged in production related to the extraction of iodine salts.
Despite the fact that there are several chemical elements in the halogen subgroup, it is iodine that has the greatest biological significance. A deficiency of this element in the human body leads to serious health problems, which is why it is so important to undergo a timely examination of the thyroid gland.
Doctors note with concern that recently there has been an increase in patients among children and adolescents.
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