The chemical element magnesium (Mg) - characteristics, structure and properties of the metal. What group of metal alloys does magnesium belong to?

Features of Mg as an element of the periodic table

The chemical properties of magnesium largely lie somewhere between beryllium and calcium. First of all, this manifests itself in interaction with water. The first does not react with it at all, while the second dissolves in it. Mg reacts weakly with heated water. But when interacting with water vapor (from 400 degrees Celsius), the reaction Mg + H2O = MgO + H2 , in which the metal dissolves with the active release of hydrogen.

Video - chemical properties of magnesium:

A slightly different reaction occurs with water vapor: Mg+ 2H2O = Mg(OH)2 + H2. Moreover, free hydrogen is ultimately absorbed by magnesium MgH3. As a result, if the metal melted in a humid environment, as it solidified, the hydrogen almost completely disappeared.

Properties of magnesium : it interacts with water at high temperatures and begins to burn in the presence of carbon dioxide in the atmosphere - making it difficult to extinguish fires involving Mg. They cannot be extinguished with water. According to the instructions, use powder fire extinguishers and sand. You can also use Si oxides, with which magnesium reacts, but the amount of heat generated is much lower.

In the photo: magnesium combustion

It should also be noted that despite the actual insolubility of Mg(OH)2 in water, a solution of phenolphthalein in its presence turns pink.

Magnesium in the periodic table

Magnesium metal is resistant to caustic alkalis, soda, kerosene, gasoline, and mineral oils. The ability of this element to remove oxygen and chlorine is used to restore pure substances. For example, bromine or titanium.

For the synthesis of different classes of organic compounds, the property of magnesium to interact with halogens is used. Typically, Cl, Br, I, with fluorine Mg forms a protective film, which is why their compound is rarely used for the synthesis of Grignard reagents. The latter are most often formed based on the formula RMgHal, where R is an organic radical and Hal is one of the listed halogens.

Which metal reacts with alkalis?

Alkali metals are elements of group 1 of the periodic table of chemical elements (according to the outdated classification - elements of the main subgroup of group I): lithium Li, sodium Na, potassium K, rubidium Rb, cesium Cs, francium Fr.

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Story

European scientists experimented with ore in the 18th and early 19th centuries. It was possible to obtain only highly contaminated substances.

The real history of the discovery begins in the mid-19th century, when the Frenchman A. Bussy and the Englishman M. Faraday obtained material of a sufficient degree of purity. Both used molten magnesium chloride. The first reduced the substance with metallic potassium, the second - by electrolysis.

The history of the name of the substance dates back to the times of Asia Minor. Magnesia was the name of a city near which deposits of magnesite were discovered.

In Russia, the term " magnesium " has been used since the mid-19th century.

Magnesium atom and molecule. Magnesium formula. Structure of magnesium

Magnesium (Latin Magnesium, from ancient Greek βαρύς - “heavy”) is a chemical element of D. I. Mendeleev’s periodic system of chemical elements with the designation Mg and atomic number 12. Located in the 2nd group (according to the old classification - the main subgroup of the second group), the third period of the periodic table.

Magnesium is an alkaline earth metal. Belongs to the group of non-ferrous metals.

As a simple substance, magnesium under normal conditions is a light, malleable metal of a silvery-white color.

The magnesium molecule is monoatomic.

The chemical formula of magnesium is Mg.

The electronic configuration of the magnesium atom is 1s2 2s2 2p6 3s2. The ionization potential (first electron) of the magnesium atom is 737.75 kJ/mol (7.646236(4) eV).

Structure of the magnesium atom. The magnesium atom consists of a positively charged nucleus (+12), around which 12 electrons move through three atomic shells. In this case, 10 electrons are in the internal level, and 2 electrons are in the external level. Since magnesium is located in the third period, there are only three shells. First, the inner shell is represented by the s-orbital. The second – the inner shell is represented by s- and p-orbitals. The third - outer shell is represented by the s-orbital. At the outer energy level of the magnesium atom, the 3s orbital contains two paired electrons. In turn, the nucleus of a magnesium atom consists of 12 protons and 12 neutrons. Magnesium belongs to the elements of the s-family.

The radius of the magnesium atom (calculated) is 145 pm.

The atomic mass magnesium atom is 24.304-24.307 a. eat.

Excess and deficiency

Magnesium is practically harmless to the body, although some of its compounds are assigned hazard class II. Basically, metal in different forms brings only benefits. And people, animals and plants most often suffer from a lack or excess of the substance.

When there is too little metal in the body, the risk of developing diabetes, kidney and intestinal diseases increases. People suffering from a lack of microelements often have headaches, insomnia, muscle spasms, and fatigue quickly sets in. If left untreated, this can lead to various more serious diseases, increasing the risk of cancer.

Before you begin to restore the level of a substance in the body, you must consult a doctor and determine the degree of need for the substance. After passing the tests, the doctor will prescribe a variable or constant intake of appropriate medications over a period of time, which should be taken strictly according to the instructions.

When there is an excess of microelement, people develop the following diseases:

• arthritis;
• speech disorder;
• nausea;
• drowsiness;
• and so on.

When the soil contains insufficient amounts of the substance, plants begin to develop leaf marbling and chlorosis. Lack of magnesium in the diet causes grass tetany in cattle.

Magnesium is one of the vital microelements. It is difficult to overestimate the role of this substance in animal and plant organisms. Its absence in sufficient quantities can cause many diseases.

Obtaining pure metal

Industrial metal production is possible in two ways:

1. Electrolytic.
2. Thermal.

The first method requires dehydrated magnesium, sodium, and potassium chlorides. They are mixed in an electrolytic bath, and magnesium is reduced in the melt.

The pure metal is drained, adding raw materials to the bath. The rough metal contains up to 2% impurities. If necessary, magnesium that has not yet cooled down is refined, bringing the purity to almost ideal - 99.999%.

In the second method, it is preferable to use dolomite with the addition of coke as a raw material. It is possible to use sea water. The mixture is heated to 2100 degrees, magnesium vapor is distilled off and condensed.

Production of magnesium alloys

Smelting of cast magnesium alloys is carried out:

• in crucible furnaces operating on liquid fuel, gaseous fuel, electricity;
• in electric induction furnaces;
• in reverberatory furnaces.

Smelting of wrought magnesium alloys is carried out:

• in reverberatory furnaces (3-12 t);
• in induction furnaces (more than 12 tons).

During the smelting of a magnesium alloy, its surface is heavily protected with a layer of flux to prevent contact with oxygen. Fluxes made on the basis of fluorine and chlorine salts, as well as alkali metals, are used. Special additives are also introduced into molding mixtures to avoid burning of the alloy.

Further processing of cast alloys is carried out in the following ways:

• sand casting - the production of castings by pouring metal into specially prepared casting models, where the future voids of the product are filled with sand;
• chill casting – production of castings in collapsible molds suitable for repeated use;
• injection molding - making castings by injecting metal into a mold under pressure.

Further processing of deformable alloys is carried out in the following ways:

• pressing - processing an alloy by pressure by squeezing it out of a closed cavity;
• forging – processing of an alloy by pressure by applying a high impact load to it;
• stamping – processing of an alloy by pressure through directed plastic deformation;
• hot rolling - processing of an alloy by pressure by passing it between pressure rolls at high temperatures;
• cold rolling - processing of an alloy by pressure by passing it between pressure rolls at low temperatures.

Methods for processing finished products to improve their mechanical properties:

• hardening (homogenization);
• hardening with artificial aging;
• annealing to relieve mechanical stress (recrystallization);
• annealing to level the metal structure and reduce grain size (diffuse).

Receipt in industry

In industrial conditions, electrolysis of anhydrous chloride or anhydrous carnallite is most often used to obtain magnesium. The process goes like this:

1. Electrolysis takes place at temperatures from 720 to 750 °C.
2. As the elements are isolated, the composition of the bath is adjusted, part of the electrolyte is removed, and raw materials are added.
3. The molten metal of interest floats to the surface and is regularly removed.
4. The resulting substance contains many impurities. To clean the element, it undergoes refining in special furnaces under a layer of flux.
5. The purified metal is poured into molds.
6. The next purification involves sublimating the reagent several times under vacuum.

In addition to this method, metallothermic and carbon-thermal methods for producing magnesium are used in production. In the first case, briquettes from hot and decomposed dolomite are mixed with a reducing agent and heated in a vacuum at a temperature of 1300 °C. The resulting magnesium vapor forms condensate when the temperature drops to 400−500 °C. To clean the metal, use submerged arc melting or vacuum melting. The pure element is poured into molds.

When using the second method, briquettes consisting of coal and magnesium oxide are heated in electric ovens to 2100 °C. The metal that has turned into steam is distilled off and condensed.

The substance is also extracted from sea water. To do this, the raw materials are mixed in very large tanks with a suspension of calcium hydroxide, which is obtained by grinding sea shells. As a result of the chemical reaction that occurs, a special suspension is formed, which, after drying, becomes magnesium chloride. After this, the product is subjected to electrolytic processes.

In addition to sea water, water from some salt lakes can be used to distill magnesium. In the Russian Federation, such lakes are located in Crimea, the Volga region and other regions.

Properties of magnesium (table): temperature, density, pressure, etc.

History of discovery

A new era in the development of chemistry began in the 17th century. During this period, a chemist from England named Gro made a discovery that brought scientists closer to the isolation of magnesium. In 1695, during the evaporation of Epsom mineral water, he received bitter salt, which had laxative properties.

A few years later, research showed that the interaction of the substance with soda and potassium carbonate produces a white, loose powder. The same result was obtained during the calcination of a mineral that was found near the city of Magnesia in Greece. Because of this similarity, the salt came to be called white magnesia.

Magnesium itself was first obtained by Humphry Davy in 1808. The scientist carried out electrolysis of white magnesia, to which he added a small amount of water and mercuric oxide. This reaction resulted in the formation of an amalgam of metallic substance. The resulting metal, after removal, was called “magnesium.”

It should be noted that the reagent had various impurities. The pure element was discovered in 1829 by the French chemist Antoine Alexandre Brutus Bussy.

Electronic circuit of magnesium

Mg:

1s2 2s2 2p6 3s2 Short notation:
Mg:
[Ne]3s2

The magnesium atom and -1Na, +1Al, +2Si, +3P, +4S, +5Cl have the same electronic configuration

The order of filling the shells of a magnesium (Mg) atom with electrons: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p.

The 's' sublevel can have up to 2 electrons, the 's' level can have up to 6 electrons, the 'd' level can have up to 10 electrons, and the 'f' level can have up to 14 electrons.

Magnesium has 12 electrons, let's fill the electron shells in the order described above:

• 2 electrons in the 1s sublevel
• 2 electrons in the 2s sublevel
• 6 electrons in the 2p sublevel
• 2 electrons in the 3s sublevel

Valency Mg

Magnesium atoms in compounds exhibit valency II.

The valency of magnesium characterizes the ability of the Mg atom to form chemical bonds. Valence follows from the structure of the electron shell of the atom; electrons involved in the formation of chemical compounds are called valence electrons. A more extensive definition of valence is:

The number of chemical bonds by which a given atom is connected to other atoms

Valence has no sign.

Magnesium crystal lattice:

Interaction with various acids

For brevity, it's easier to look at a few experiments. The following types of acids are used for them:

1. Solyanaya.
2. Nitrogen.
3. Sulfuric (diluted and not).

In the first case, almost instantaneous dissolution is observed, accompanied by bubbles of white gases and a pungent odor of chlorine. The container in which the reaction took place heats up.

A piece of magnesium does not sink in nitric acid. Brown gas accumulates above the surface of the liquid and heat is released. The acid is sometimes said to be "boiling" around the magnesium pieces.

The third case must be considered as two particular ones. In undiluted sulfuric acid the reaction proceeds slowly. If you use a solution with a small amount of water, magnesium, just like with nitric acid, floats on the surface. In this case, a barely noticeable reaction occurs with the release of white gas bubbles.

Being in nature

Clark magnesium - 1.95% (19.5 kg/t). This is one of the most common elements of the earth's crust. Large amounts of magnesium are found in seawater in the form of a salt solution. The main minerals with a high mass content of magnesium:

• sea ​​water - (0.12-0.13%),
• carnallite - MgCl2 • KCl • 6H2O (8.7%),
• bischofite - MgCl2 • 6H2O (11.9%),
• kieserite - MgSO4 • H2O (17.6%),
• epsomite - MgSO4 • 7H2O (9.9%),
• kainite - KCl • MgSO4 • 3H2O (9.8%),
• magnesite - MgCO3 (28.7%),
• dolomite - CaCO3 MgCO3 (13.1%),
• brucite - Mg(OH)2 (41.6%).

Magnesium salts are found in large quantities in salt deposits of self-sediment lakes. Deposits of carnallite of sedimentary origin are found in many countries.

Magnesite is formed predominantly in hydrothermal conditions and belongs to medium-temperature hydrothermal deposits. Dolomite is also an important magnesium raw material. Dolomite deposits are widespread and their reserves are enormous. They are genetically related to carbonate sedimentary layers and most of them are of Precambrian or Permian geological age. Dolomite deposits are formed by sedimentation, but can also arise when limestone is exposed to hydrothermal solutions, groundwater or surface water.

An extremely rare mineral is native magnesium, formed in flows of reducing gases and first discovered in 1991 in the coastal sediments of Chona (Eastern Siberia), and then in lavas in Southern Gissar (Tajikistan).

Natural sources of magnesium

• Fossil mineral deposits (magnesian and potassium-magnesian carbonates: dolomite, magnesite).
• Sea water.
• Brines (brine of salt lakes).

In 1995, most of the world's magnesium production was concentrated in the USA (43%), CIS countries (26%) and Norway (17%), with China's share of the market increasing.

Minerals, deposits

Our hero is so chemically active (simply “promiscuous”) that it is almost impossible to find it in nature in its pure form.

Natural sources of magnesium - minerals:

• brucite;
• kieserite;
• dolomite;
• magnesite;
• bischofite;
• epsomite;
• carnallite.

Fire metal can even be extracted from sea water. Self-sedimented lakes (the water in them is called brine) contain a large amount of mineral salts, including magnesium.

Educational: there are many such lakes in the Astrakhan region. These are Belinsky, Zinzilinsky, Mochagovsky self-sedating lakes (the list goes on).

The largest Russian group of deposits - Satkinskoye - (14 explored) is located in the Chelyabinsk region, near the city of Satka. High purity magnesium ores are concentrated here.

Application

Alloys

Magnesium-based alloys are an important structural material in the aircraft and automotive industries due to their lightness and strength. Prices for magnesium bullion in 2006 averaged $3/kg.

Chemical current sources

Magnesium in the form of pure metal, as well as its chemical compounds (bromide, perchlorate) are used for the production of very powerful backup electric batteries (for example, magnesium-perchlorate cell, sulfur-magnesium cell, lead chloride-magnesium cell, silver-magnesium chloride cell, copper-magnesium chloride cell element, magnesium-vanadium element, etc.), and dry elements (manganese-magnesium element, bismuth-magnesium element, magnesium-m-DNB element, etc.). Magnesium-based CCDs are distinguished by very high specific energy characteristics and high discharge voltage. In recent years, the problem of developing a battery with a long service life has become more acute in a number of countries, since theoretical data suggest very great prospects for its widespread use (high energy, environmental friendliness, availability of raw materials).

Connections

Magnesium hydride is one of the most capacious hydrogen batteries used for hydrogen storage.

Fireproof materials

Magnesium oxide MgO is used as a refractory material for the production of crucibles and special linings of metallurgical furnaces.

Magnesium perchlorate, Mg(ClO4)2 - (anhydrone) is used for deep drying of gases in laboratories, and as an electrolyte for chemical current sources involving magnesium.

Magnesium fluoride MgF2 - in the form of synthetic single crystals is used in optics (lenses, prisms).

Magnesium bromide MgBr2 - as an electrolyte for chemical backup current sources.

Medicine

Magnesium oxide and salts are used in medicine (asparkam, magnesium sulfate, magnesium citrate, bischofite mineral). Bischophytotherapy uses the biological effects of natural magnesium in the treatment and rehabilitation of a wide range of diseases, primarily the musculoskeletal system, nervous and cardiovascular systems.

Photo

Magnesium powder with oxidizing additives (barium nitrate, ammonium nitrate, potassium permanganate, sodium hypochlorite, potassium chlorate, etc.) was used (and is now used in rare cases) in photography in chemical flashes (magnesium flash).

The benefits and harms of supplements

Pure magnesium is a malleable, lightweight metal. The only property metal has is susceptibility to corrosion. Therefore, pure metal is rarely used, unlike its alloys. For magnesium alloys, the addition of aluminum, zirconium, and zinc is very important.

Aluminum makes the alloy stronger and more convenient for foundry work.

The amount of alloy is important for the qualities of the alloy:

• 3% aluminum will give the greatest ductility;
• 6% ligature - will give better strength and ductility;
• 9% aluminum will give the alloy maximum strength.

The properties of zinc in alloys are similar to aluminum:

• 3% additive maximizes plasticity;
• 5% zinc will give a harmonious combination of ductility and strength of the alloy;

If the alloy contains harmful impurities (nickel, iron), then the zinc alloy will increase corrosion resistance.

Silicon will increase castability, but in the presence of iron will reduce rust resistance.

Nickel and iron impurities are harmful and make the alloy susceptible to rust.

Magnesium alloys are divided into wrought alloys (MA) and cast alloys (ML); the latter are used much more often. Copper, iron, zinc, and nickel are added to the MCI alloy. This mixture of metals is good under vibration loads.

Application of the substance

Metallurgy consumes the largest amount of metal. On its basis, many alloys are created. The substance is often used in metallothermic processes to obtain rare metals, as well as those that are difficult to recover. A reagent is used for deoxidation and desulfurization of metallic substances. Various magnesium-based powder mixtures are used as lighting and incendiary materials.

Compounds containing the reagent have found wide application in various spheres of life. For example, in medicine, medications with magnesium can relieve patients from spasms and convulsions, calm the nerves, and so on.

Meaning for humans

Magnesium is initially present in biological organisms. However, in everyday products (bread, milk, meat) there is a minimum of it.

Life processes

Without metal, the normal course of important life processes is impossible:

• Protein synthesis.
• The work of the nervous system and heart muscle.
• Vasodilation.
• Bile secretion.
• Work of the gastrointestinal tract.
• Removing cholesterol from the body.
• Muscle contraction.

The daily intake of the substance for women and men is 300 and 400 mg.

The need is increased by mental and physical overload, stress, alcohol abuse, and sweating.

It must be taken into account that the body absorbs only a third of the total amount of the substance ingested.

Phytin, fatty or calcium-rich diets interfere with the absorption of microelements more fully.

Toxicology

Magnesium compounds are low-toxic (with the exception of salts of such toxic acids as hydrocyanic, hydronitrous, hydrofluoric, chromic).

Biological role

Magnesium is one of the important biogenic elements; it is found in significant quantities in the tissues of animals and plants (chlorophylls). Its biological role was formed historically during the period of the origin and development of protolife on our planet due to the fact that the salt composition of the sea water of the ancient Earth was predominantly magnesium chloride, in contrast to the current one - sodium chloride.

Magnesium is a cofactor in many enzymatic reactions. Magnesium is necessary for the conversion of creatine phosphate into ATP, a nucleotide that is a universal supplier of energy in living cells of the body. Magnesium is necessary at all stages of protein synthesis. It is involved in maintaining the normal function of the nervous system and heart muscles, has a vasodilating effect, stimulates bile secretion, increases intestinal motor activity, which helps remove cholesterol from the body.

The absorption of magnesium is hindered by the presence of phytin and excess fat and calcium in food. A lack of magnesium in the body can manifest itself in different ways: insomnia, chronic fatigue, osteoporosis, arthritis, fibromyalgia, migraine, muscle cramps and spasms, cardiac arrhythmia, constipation, premenstrual syndrome (PMS). With sweating, frequent use of laxatives and diuretics, alcohol, great mental and physical stress (primarily under stress and in athletes), the need for magnesium increases.

Most magnesium is found in wheat bran, pumpkin seeds, and cocoa powder. Foods rich in magnesium also include sesame, bran, and nuts. However, the abundance of phytin in these foods makes it difficult to absorb, so only green vegetables can serve as a reliable source of magnesium. There is very little magnesium in bread, dairy, meat and other everyday food products of modern people. The daily requirement of magnesium is about 300 mg for women and 400 mg for men (it is assumed that about 30% of magnesium is absorbed).

When consuming vitamin-mineral complexes containing magnesium, it must be remembered that if it is consumed excessively, an overdose is possible, accompanied by a decrease in blood pressure, nausea, vomiting, depression of the central nervous system, decreased reflexes, changes in the electrocardiogram, respiratory depression, coma, cardiac arrest, respiratory paralysis, anuric syndrome.

People with kidney failure should also be careful when taking magnesium.

Nutrition

Cocoa powder, bran, nuts, and pumpkin seeds are saturated with magnesium. However, the abundance of phytin in them interferes with the absorption of the element.

Nutritionists consider green vegetables to be a storehouse of magnesium. These are cabbage, cucumbers, peas, asparagus, celery, onions, spinach, parsley.

Consequences of deficiency or excess of a substance

Symptoms of magnesium deficiency:

Magnesium in organisms

Magnesium is found in all plants and animals. The substance is concentrated in some marine organisms. The maximum amount of metal element is contained in lime sponges - up to 4%.

This reagent is also part of the chlorophyll of green plants . In total, they account for 100 billion tons of the substance. Scientists have discovered magnesium in all components necessary for the cells of living organisms to exist. This element triggers many enzymes and allows plant chromosomes and colloidal systems to remain stable. In addition, the reagent maintains turgor pressure in cells. Thanks to magnesium, plants better absorb and assimilate phosphorus in the soil.

People and animals obtain the metal element through food. The daily intake for humans is from 0.3 to 0.5 g. In children and pregnant women, the need for the substance is slightly higher. A healthy person should have about 4.3 mg/% magnesium in their blood. In the body, the main consumer of the reagent is the liver, but most of the metal absorbed by it gradually passes into the bones and muscles.