Calcium he 2. Calcium (chemical element)
Calcium is located in the fourth large period, the second group, the main subgroup, the element's serial number is 20. According to Mendeleev's periodic table, the atomic weight of calcium is 40.08. The formula of the highest oxide is CaO. Calcium has a Latin name calcium, so the element's atom symbol is Ca.
Characterization of calcium as a simple substance
Under normal conditions, calcium is a silvery-white metal. Having a high chemical activity, the element is able to form many compounds of different classes. The element is of value for technical and industrial chemical syntheses. The metal is widely distributed in the earth's crust: its share is about 1.5%. Calcium belongs to the group of alkaline earth metals: when dissolved in water, it gives alkalis, but in nature it occurs in the form of multiple minerals and. Sea water contains calcium in high concentrations (400 mg/l).
pure sodiumThe characteristics of calcium depend on the structure of its crystal lattice. This element has two types of it: cubic face-centric and volume-centric. The type of bond in the molecule is metallic.
Natural sources of calcium:
- apatite;
- alabaster;
- gypsum;
- calcite;
- fluorite;
- dolomite.
Physical properties of calcium and methods for producing metal
Under normal conditions, calcium is in a solid state of aggregation. The metal melts at 842 °C. Calcium is a good electrical and thermal conductor. When heated, it passes first into a liquid, and then into a vapor state and loses its metallic properties. The metal is very soft and can be cut with a knife. Boils at 1484 °C.
Under pressure, calcium loses its metallic properties and electrical conductivity. But then the metallic properties are restored and the properties of a superconductor appear, several times greater than the rest in their performance.
For a long time it was not possible to obtain calcium without impurities: due to its high chemical activity, this element does not occur in nature in its pure form. The element was discovered at the beginning of the 19th century. Calcium as a metal was first synthesized by the British chemist Humphrey Davy. The scientist discovered the features of the interaction of melts of solid minerals and salts with an electric current. Nowadays, the electrolysis of calcium salts (mixtures of calcium and potassium chlorides, mixtures of calcium fluoride and calcium chloride) remains the most relevant method for producing metal. Calcium is also extracted from its oxide using aluminothermy, a method common in metallurgy.
Chemical properties of calcium
Calcium is an active metal that enters into many interactions. Under normal conditions, it easily reacts, forming the corresponding binary compounds: with oxygen, halogens. Click to learn more about calcium compounds. When heated, calcium reacts with nitrogen, hydrogen, carbon, silicon, boron, phosphorus, sulfur and other substances. In the open air, it instantly interacts with oxygen and carbon dioxide, therefore it becomes covered with a gray coating.
Reacts violently with acids, sometimes igniting. In salts, calcium exhibits interesting properties. For example, cave stalactites and stalagmites are calcium carbonate, gradually formed from water, carbon dioxide and bicarbonate as a result of processes inside groundwater.
Due to its high activity in the normal state, calcium is stored in laboratories in dark sealed glassware under a layer of paraffin or kerosene. A qualitative reaction to the calcium ion is the coloring of the flame in a rich brick-red color.
Calcium turns the flame red
The metal in the composition of compounds can be identified by insoluble precipitates of some salts of the element (fluoride, carbonate, sulfate, silicate, phosphate, sulfite).
The reaction of water with calcium
Calcium is stored in jars under a layer of protective liquid. To conduct, demonstrating how the reaction of water and calcium occurs, you cannot just get the metal and cut off the desired piece from it. Metallic calcium in the laboratory is easier to use in the form of shavings.
If there are no metal shavings, and there are only large pieces of calcium in the bank, pliers or a hammer will be required. The finished piece of calcium of the desired size is placed in a flask or glass of water. Calcium shavings are placed in a dish in a gauze bag.
Calcium sinks to the bottom, and hydrogen evolution begins (first, in the place where the fresh fracture of the metal is located). Gradually, gas is released from the calcium surface. The process resembles rapid boiling, at the same time a precipitate of calcium hydroxide (slaked lime) is formed.
lime slaking
A piece of calcium floats up, picked up by bubbles of hydrogen. After about 30 seconds, the calcium dissolves and the water turns cloudy white due to the formation of hydroxide slurry. If the reaction is carried out not in a beaker, but in a test tube, heat evolution can be observed: the test tube quickly becomes hot. The reaction of calcium with water does not end with a spectacular explosion, but the interaction of the two substances proceeds violently and looks spectacular. The experience is safe.
If the bag with the remaining calcium is removed from the water and held in the air, then after a while, as a result of the ongoing reaction, strong heating will occur and the remaining in the gauze will boil. If part of the cloudy solution is filtered through a funnel into a beaker, then when carbon monoxide CO₂ is passed through the solution, a precipitate will form. This does not require carbon dioxide - you can blow exhaled air into the solution through a glass tube.
Calcium- an element of the 4th period and the PA group of the Periodic System, serial number 20. The electronic formula of the atom is [ 18 Ar] 4s 2, oxidation states +2 and 0. Refers to alkaline earth metals. It has a low electronegativity (1.04), exhibits metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Many calcium salts are sparingly soluble in water. In nature - sixth in terms of chemical abundance, the element (the third among metals) is in a bound form. A vital element for all organisms. The lack of calcium in the soil is replenished by the application of lime fertilizers (CaCO 3 , CaO, calcium cyanamide CaCN 2, etc.). Calcium, calcium cation and its compounds color the flame of a gas burner in a dark orange color ( qualitative detection).
Calcium Ca
Silver-white metal, soft, ductile. In humid air, it tarnishes and becomes covered with a film of CaO and Ca(OH) 2. Very reactive; ignites when heated in air, reacts with hydrogen, chlorine, sulfur and graphite:
Reduces other metals from their oxides (an industrially important method is calciumthermy):
Receipt calcium in industry:
Calcium is used to remove non-metal impurities from metal alloys, as a component of light and antifriction alloys, to isolate rare metals from their oxides.
Calcium oxide CaO
basic oxide. The technical name is quicklime. White, highly hygroscopic. Has an ionic structure Ca 2+ O 2- . Refractory, thermally stable, volatile on ignition. Absorbs moisture and carbon dioxide from the air. Reacts vigorously with water (high exo- effect), forms a strongly alkaline solution (hydroxide precipitation is possible), the process is called lime slaking. Reacts with acids, metal and non-metal oxides. It is used for the synthesis of other calcium compounds, in the production of Ca(OH) 2 , CaC 2 and mineral fertilizers, as a flux in metallurgy, a catalyst in organic synthesis, a component of binders in construction.
Equations of the most important reactions:
Receipt Cao in industry– limestone roasting (900-1200 °С):
CaCO3 = CaO + CO2
Calcium hydroxide Ca(OH) 2
basic hydroxide. The technical name is slaked lime. White, hygroscopic. It has an ionic structure Ca 2+ (OH -) 2. Decomposes on moderate heat. Absorbs moisture and carbon dioxide from the air. Slightly soluble in cold water (an alkaline solution is formed), even less so in boiling water. A clear solution (lime water) quickly becomes cloudy due to the precipitation of hydroxide (the suspension is called milk of lime). A qualitative reaction to the Ca 2+ ion is the passage of carbon dioxide through lime water with the appearance of a precipitate of CaCO 3 and its transition into solution. Reacts with acids and acid oxides, enters into ion exchange reactions. It is used in the production of glass, bleaching lime, lime mineral fertilizers, for causticizing soda and softening fresh water, as well as for the preparation of lime mortars - pasty mixtures (sand + slaked lime + water), serving as a binder for stone and brickwork, finishing ( plastering) walls and other construction purposes. The hardening ("seizure") of such solutions is due to the absorption of carbon dioxide from the air.
CALCIUM (Latin Calcium), Ca, a chemical element of group II of the short form (2nd group of the long form) of the periodic system; refers to alkaline earth metals; atomic number 20; atomic mass 40.078. In nature, there are 6 stable isotopes: 40 Ca (96.941%), 42 Ca (0.647%), 43 Ca (0.135%), 44 Ca (2.086%), 46 Ca (0.004%), 48 Ca (0.187%); artificially obtained radioisotopes with mass numbers 34-54.
History reference. Many natural calcium compounds were known in ancient times and were widely used in construction (for example, gypsum, lime, marble). Metallic calcium was first isolated by G. Davy in 1808 during the electrolysis of a mixture of CaO and HgO oxides and subsequent decomposition of the formed calcium amalgam. The name comes from the Latin calx (genitive calcis) - lime, soft stone.
Distribution in nature. The calcium content in the earth's crust is 3.38% by mass. Due to its high chemical activity, it does not occur in the free state. The most common minerals are anorthite Ca, anhydrite CaSO 4, apatite Ca 5 (PO 4) 3 (F, Cl, OH), gypsum CaSO 4 2H 2 O, calcite and aragonite CaCO 3, perovskite CaTiO 3, fluorite CaF 2, scheelite CaWO 4 . Calcium minerals are part of sedimentary (for example, limestone), igneous and metamorphic rocks. Calcium compounds are found in living organisms: they are the main components of the bone tissues of vertebrates (hydroxyapatite, fluorapatite), coral skeletons, mollusk shells (calcium carbonate and phosphates), etc. The presence of Ca 2+ ions determines the hardness of water.
Properties. The configuration of the outer electron shell of the calcium atom is 4s 2 ; in compounds it exhibits an oxidation state of +2, rarely +1; Pauling electronegativity 1.00, atomic radius 180 pm, Ca 2+ ion radius 114 pm (coordination number 6). calcium is a silvery-white soft metal; up to 443 °С, the modification with a cubic face-centered crystal lattice is stable, above 443 °С - with a cubic body-centered lattice; t pl 842°С, t kip 1484 °С, density 1550 kg/m3; thermal conductivity 125.6 W/(m K).
Calcium is a metal of high chemical activity (stored in hermetically sealed vessels or under a layer of mineral oil). Under normal conditions, it easily interacts with oxygen (calcium oxide CaO is formed), when heated - with hydrogen (CaH 2 hydride), halogens (calcium halides), boron (CaB 6 boride), carbon (calcium carbide CaC 2), silicon (Ca silicides 2 Si, CaSi, CaSi 2, Ca 3 Si 4), nitrogen (Ca 3 N 2 nitride), phosphorus (Ca 3 P 2, CaP, CaP 5 phosphides), chalcogens (CaX chalcogenides, where X is S, Se, Those). Calcium interacts with other metals (Li, Cu, Ag, Au, Mg, Zn, Al, Pb, Sn, etc.) to form intermetallic compounds. Metallic calcium reacts with water to form calcium hydroxide Ca(OH) 2 and H 2 . Vigorously interacts with most acids, forming the corresponding salts (for example, calcium nitrate, calcium sulfate, calcium phosphates). It dissolves in liquid ammonia to form a dark blue solution with metallic conductivity. When ammonia evaporates, ammonia is released from such a solution. Gradually, calcium reacts with ammonia to form the amide Ca(NH 2) 2 . It forms various complex compounds, complexes with oxygen-containing polydentate ligands, for example Ca complexonates, are of the greatest importance.
Biological role. Calcium refers to biogenic elements. The daily human need for calcium is about 1 g. In living organisms, calcium ions are involved in the processes of muscle contraction and the transmission of nerve impulses.
Receipt. Calcium metal is obtained by electrolytic and metallothermic methods. The electrolytic method is based on the electrolysis of molten calcium chloride with a touch cathode or a liquid copper-calcium cathode. Calcium is distilled off from the resulting copper-calcium alloy at a temperature of 1000-1080 °C and a pressure of 13-20 kPa. The metallothermic method is based on the reduction of calcium from its oxide with aluminum or silicon at 1100-1200 °C. This produces aluminate or calcium silicate, as well as gaseous calcium, which is then condensed. World production of calcium compounds and materials containing calcium, about 1 billion tons/year (1998).
Application. Calcium is used as a reducing agent in the production of many metals (Rb, Cs, Zr, Hf, V, etc.). Calcium silicides, as well as calcium alloys with sodium, zinc and other metals, are used as deoxidizers and desulfurizers for some alloys and oil, for purifying argon from oxygen and nitrogen, and as a gas absorber in vacuum devices. CaCl 2 chloride is used as a drying agent in chemical synthesis, gypsum is used in medicine. Calcium silicates are the main components of cement.
Lit .: Rodyakin VV Calcium, its compounds and alloys. M., 1967; Spitsyn V.I., Martynenko L.I. Inorganic chemistry. M., 1994. Part 2; Inorganic Chemistry / Edited by Yu. D. Tretyakov. M., 2004. T. 2.
L. N. Komissarova, M. A. Ryumin.
Calcium(Calcium), Ca, a chemical element of group II of the Mendeleev periodic system, atomic number 20, atomic mass 40.08; silver-white light metal. The natural element is a mixture of six stable isotopes: 40 Ca, 42 Ca, 43 Ca, 44 Ca, 46 Ca and 48 Ca, of which 40 Ca is the most common (96.97%).
Ca compounds - limestone, marble, gypsum (as well as lime - a product of burning limestone) have been used in construction since ancient times. Until the end of the 18th century, chemists considered lime to be a simple substance. In 1789, A. Lavoisier suggested that lime, magnesia, barite, alumina and silica are complex substances. In 1808, G. Davy, subjecting a mixture of wet slaked lime with mercury oxide to electrolysis with a mercury cathode, prepared an amalgam of Ca, and after driving mercury out of it, he obtained a metal called "Calcium" (from Latin calx, genus case calcis - lime) .
Distribution of calcium in nature. In terms of abundance in the earth's crust, Ca occupies the 5th place (after O, Si, Al, and Fe); content 2.96% by weight. It migrates vigorously and accumulates in various geochemical systems, forming 385 minerals (4th place in terms of the number of minerals). There is little Ca in the Earth's mantle and, probably, even less in the Earth's core (0.02% in iron meteorites). Ca predominates in the lower part of the earth's crust, accumulating in basic rocks; most of Ca is enclosed in feldspar - anorthite Ca; content in basic rocks 6.72%, in acidic (granites and others) 1.58%. An exceptionally sharp differentiation of Ca occurs in the biosphere, mainly associated with the "carbonate equilibrium": when carbon dioxide interacts with CaCO 3 carbonate, soluble bicarbonate Ca (HCO 3) 2 is formed: CaCO 3 + H 2 O + CO 2 \u003d Ca (HCO 3) 2 \u003d Ca 2+ + 2HCO 3-. This reaction is reversible and is the basis of Ca redistribution. With a high content of CO 2 in the waters, Ca is in solution, and with a low content of CO 2, the mineral calcite CaCO 3 precipitates, forming powerful deposits of limestone, chalk, and marble.
Biogenic migration also plays a huge role in the history of Ca. In living matter from elements-metals, Ca is the main one. Organisms are known that contain more than 10% Ca (more carbon), building their skeleton from Ca compounds, mainly from CaCO 3 (calcareous algae, many molluscs, echinoderms, corals, rhizomes, etc.). With the burial of the skeletons of the sea. Animals and plants are associated with the accumulation of colossal masses of algae, coral and other limestones, which, plunging into the depths of the earth and mineralizing, turn into various types of marble.
Huge areas with a humid climate (forest zones, tundra) are characterized by a deficiency of Ca - here it is easily leached from the soil. This is associated with low soil fertility, low productivity of domestic animals, their small size, and often skeletal diseases. Therefore, liming of soils, feeding domestic animals and birds, etc. is of great importance. On the contrary, CaCO 3 is sparingly soluble in a dry climate, therefore steppe and desert landscapes are rich in Ca. Gypsum CaSO 4 2H 2 O often accumulates in salt marshes and salt lakes.
Rivers bring a lot of Ca into the ocean, but it does not linger in ocean water (average content is 0.04%), but is concentrated in the skeletons of organisms and, after their death, is deposited on the bottom mainly in the form of CaCO 3 . Lime silts are widespread on the bottom of all oceans at depths of no more than 4000 m (CaCO 3 dissolves at great depths, organisms there often experience a deficiency of Ca).
Groundwater plays an important role in Ca migration. In limestone massifs, they vigorously leach CaCO 3 in places, which is associated with the development of karst, the formation of caves, stalactites and stalagmites. In addition to calcite, in the seas of past geological epochs, the deposition of Ca phosphates (for example, the Karatau phosphorite deposits in Kazakhstan), dolomite CaCO 3 ·MgCO 3, and gypsum during evaporation were widespread in the seas of past geological epochs.
In the course of geological history, biogenic carbonate formation increased, while the chemical precipitation of calcite decreased. In the Precambrian seas (over 600 million years ago) there were no animals with a calcareous skeleton; they have become widespread since the Cambrian (corals, sponges, etc.). This is attributed to the high content of CO 2 in the Precambrian atmosphere.
Physical properties of calcium. The crystal lattice of the α-form of Ca (stable at ordinary temperature) is face-centered cubic, a = 5.56Å. Atomic radius 1.97Å, ionic radius Ca 2+ 1.04Å. Density 1.54 g/cm3 (20 °C). Above 464 °C, the hexagonal β-form is stable. t pl 851 °C, t kip 1482 °C; temperature coefficient of linear expansion 22 10 -6 (0-300 °C); thermal conductivity at 20 °C 125.6 W/(m K) or 0.3 cal/(cm s °C); specific heat capacity (0-100 °C) 623.9 j/(kg K) or 0.149 cal/(g °C); electrical resistivity at 20 °C 4.6 10 -8 ohm m or 4.6 10 -6 ohm cm; temperature coefficient of electrical resistance 4.57 10 -3 (20 °C). Modulus of elasticity 26 Gn / m 2 (2600 kgf / mm 2); tensile strength 60 MN / m 2 (6 kgf / mm 2); elastic limit 4 MN / m 2 (0.4 kgf / mm 2), yield strength 38 MN / m 2 (3.8 kgf / mm 2); elongation 50%; Brinell hardness 200-300 MN / m 2 (20-30 kgf / mm 2). Calcium of sufficiently high purity is plastic, well pressed, rolled and can be machined.
Chemical properties of calcium. The configuration of the outer electron shell of the Ca 4s 2 atom, according to which Ca in compounds is 2-valent. Chemically Ca is very active. At ordinary temperatures, Ca easily interacts with oxygen and moisture in the air, so it is stored in hermetically sealed vessels or under mineral oil. When heated in air or oxygen, it ignites, giving the basic oxide CaO. Peroxides Ca-CaO 2 and CaO 4 are also known. At first, Ca reacts rapidly with cold water, then the reaction slows down due to the formation of a Ca(OH) 2 film. Ca reacts vigorously with hot water and acids, releasing H 2 (except for concentrated HNO 3). It reacts with fluorine in the cold, and with chlorine and bromine - above 400 ° C, giving CaF 2, CaCl 2 and CaBr 2, respectively. These halides in the molten state form with Ca the so-called subcompounds - CaF, CaCl, in which Ca is formally monovalent. When Ca is heated with sulfur, calcium sulfide CaS is obtained, the latter adds sulfur, forming polysulfides (CaS 2, CaS 4 and others). Interacting with dry hydrogen at 300-400 ° C, Ca forms a hydride CaH 2 - an ionic compound in which hydrogen is an anion. At 500 °C Ca and nitrogen give Ca 3 N 2 nitride; the interaction of Ca with ammonia in the cold leads to the complex ammonia Ca 6 . When heated without access to air with graphite, silicon or phosphorus, Ca gives calcium carbide CaC 2 , silicides Ca 2 Si, CaSi, CaSi 2 and phosphide Ca 3 P 2 , respectively. Ca forms intermetallic compounds with Al, Ag, Au, Cu, Li, Mg, Pb, Sn and others.
Getting Calcium. In industry, Ca is obtained in two ways: 1) by heating a briquetted mixture of CaO and Al powder at 1200 ° C in a vacuum of 0.01-0.02 mm Hg. Art.; released by the reaction: 6CaO + 2 Al \u003d 3CaO Al 2 O 3 + 3Ca Ca vapor condenses on a cold surface; 2) by electrolysis of a melt of CaCl 2 and KCl with a liquid copper-calcium cathode, an alloy of Cu - Ca (65% Ca) is prepared, from which Ca is distilled off at a temperature of 950-1000 ° C in a vacuum of 0.1-0.001 mm Hg. Art.
The use of calcium. In the form of a pure metal, Ca is used as a reducing agent for U, Th, Cr, V, Zr, Cs, Rb and some rare earth metals from their compounds. It is also used for the deoxidation of steels, bronzes and other alloys, for the removal of sulfur from petroleum products, for the dehydration of organic liquids, for the purification of argon from nitrogen impurities, and as a gas absorber in electric vacuum devices. Antifriction materials of the Pb-Na-Ca system, as well as Pb-Ca alloys, which are used for the manufacture of electrical shells, have received great application in technology. cables. Alloy Ca-Si-Ca (silicocalcium) is used as a deoxidizer and degasser in the production of high-quality steels.
calcium in the body. Ca is one of the biogenic elements necessary for the normal course of life processes. It is present in all tissues and fluids of animals and plants. Only rare organisms can develop in an environment devoid of Ca. In some organisms, the Ca content reaches 38%; in humans - 1.4-2%. Cells of plant and animal organisms need strictly defined ratios of Ca 2+ , Na + and K + ions in extracellular media. Plants get Ca from the soil. According to their relationship to Ca, plants are divided into calcephiles and calcephobes. Animals get Ca from food and water. Ca is necessary for the formation of a number of cellular structures, maintaining the normal permeability of outer cell membranes, for fertilizing the eggs of fish and other animals, and for activating a number of enzymes. Ca 2+ ions transmit excitation to the muscle fiber, causing it to contract, increase the strength of heart contractions, increase the phagocytic function of leukocytes, activate the system of protective blood proteins, and participate in its coagulation. In cells, almost all Ca is in the form of compounds with proteins, nucleic acids, phospholipids, in complexes with inorganic phosphates and organic acids. In the blood plasma of humans and higher animals, only 20-40% Ca can be associated with proteins. In animals with a skeleton, up to 97-99% of all Ca is used as a building material: in invertebrates, mainly in the form of CaCO 3 (mollusk shells, corals), in vertebrates, in the form of phosphates. Many invertebrates store Ca before molting to build a new skeleton or to provide vital functions in adverse conditions.
The content of Ca in the blood of humans and higher animals is regulated by the hormones of the parathyroid and thyroid glands. Vitamin D plays the most important role in these processes. Ca absorption occurs in the anterior part of the small intestine. Assimilation of Ca worsens with a decrease in acidity in the intestine and depends on the ratio of Ca, P and fat in food. The optimal Ca / P ratio in cow's milk is about 1.3 (in potatoes 0.15, in beans 0.13, in meat 0.016). With an excess of P or oxalic acid in food, Ca absorption deteriorates. Bile acids accelerate its absorption. The optimal Ca/fat ratio in human food is 0.04-0.08 g of Ca per 1 g of fat. Excretion of Ca occurs mainly through the intestines. Mammals during lactation lose a lot of Ca with milk. With violations of phosphorus-calcium metabolism in young animals and children, rickets develop, in adult animals - a change in the composition and structure of the skeleton (osteomalacia).
The bone skeleton is composed of it, but the body is not able to produce the element on its own. It's about calcium. Adult women and men need to get at least 800 milligrams of alkaline earth metal per day. It is possible to extract it from oatmeal, hazelnuts, milk, barley groats, sour cream, beans, almonds.
Calcium found in peas, mustard, cottage cheese. True, if you combine them with sweets, coffee, cola and foods rich in oxalic acid, the digestibility of the element drops.
The gastric environment becomes alkaline, calcium is captured in insoluble and excreted from the body. Bones and teeth begin to break down. What is it about an element, since it has become one of the most important for living beings, and is there a use for the substance outside their organisms?
Chemical and physical properties of calcium
In the periodic table, the element occupies the 20th place. It is in the main subgroup of the 2nd group. The period to which calcium belongs is the 4th. This means that an atom of matter has 4 electronic levels. They have 20 electrons, which is indicated by the atomic number of the element. It also testifies to its charge - +20.
calcium in the body, as in nature, is an alkaline earth metal. This means that in its pure form, the element is silver-white, shiny and light. The hardness of alkaline earth metals is higher than that of alkali metals.
The calcium index is about 3 points according to. Gypsum, for example, has the same hardness. The 20th element is cut with a knife, but much more difficult than any of the simple alkali metals.
What is the meaning of the name "alkaline earth"? So calcium and other metals of his group were dubbed by alchemists. They called the oxides of the elements earths. Oxides of substances calcium groups make the water alkaline.
However, , radium, barium, as well as the 20th element, are found not only in combination with oxygen. There are many calcium salts in nature. The most famous of them is the mineral calcite. The carbonic form of the metal is the notorious chalk, limestone and gypsum. Each of them is calcium carbonate.
The 20th element also has volatile compounds. They color the flame orange-red, which becomes one of the markers for identifying substances.
All alkaline earth metals burn easily. In order for calcium to react with oxygen, normal conditions are sufficient. Only in nature, the element does not occur in its pure form, only in compounds.
Calcium oxy- a film that covers the metal, if it is in the air. The coating is yellowish. It contains not only standard oxides, but also peroxides, nitrides. If calcium is not exposed to air, but to water, it will displace hydrogen from it.
At the same time, the precipitate calcium hydroxide. Remains of pure metal float to the surface, pushed by hydrogen bubbles. The same scheme works with acids. With hydrochloric acid, for example, it precipitates calcium chloride and hydrogen is released.
Some reactions require elevated temperatures. If it gets to 842 degrees, calcium can melt. At 1484 on the Celsius scale, the metal boils.
calcium solution, like a pure element, conducts heat and electric current well. But, if the substance is very hot, the metallic properties are lost. That is, neither molten nor gaseous calcium has them.
In the human body, the element is represented by both solid and liquid states of aggregation. Softened calcium water, which is present in, transfers more easily. Outside the bones is only 1% of the 20th substance.
However, its transport through tissues plays an important role. Calcium in the blood regulates muscle contraction, including heart muscle, maintains normal blood pressure.
Application of calcium
In its pure form, the metal is used in. They go to battery grids. The presence of calcium in the alloy reduces the self-discharge of batteries by 10-13%. This is especially important for stationary models. Bearings are also made from a mixture of lead and the 20th element. One of the alloys is called bearing.
Pictured are calcium-rich foods.
An alkaline earth metal is added to steel to purify the alloy from sulfur impurities. The reducing properties of calcium are also useful in the production of uranium, chromium, cesium, rubidium,.
What kind of calcium used in ferrous metallurgy? All the same pure. The difference is in the purpose of the element. Now, he's playing the part. It is an additive to alloys that reduces the temperature of their formation and facilitates the separation of slags. calcium granules fall asleep in electrovacuum devices to remove traces of air from them.
The 48th isotope of calcium is in demand at nuclear enterprises. Superheavy elements are produced there. Raw materials are obtained at nuclear accelerators. Disperse them with the help of ions - a kind of projectiles. If Ca48 acts in their role, the efficiency of synthesis increases hundreds of times in comparison with the use of ions of other substances.
In optics, the 20th element is already valued as compounds. Fluoride and calcium tungstate become lenses, objectives and prisms of astronomical instruments. Minerals are also found in laser technology.
Geologists call calcium fluoride fluorite, and wolframide - scheelite. For the optical industry, their single crystals are selected, that is, separate, large aggregates with a continuous lattice and a clear shape.
In medicine, they also prescribe not pure metal, but substances based on it. They are more easily absorbed by the body. Calcium gluconate- the cheapest remedy used for osteoporosis. A drug " Calcium Magnesium"prescribed to adolescents, pregnant women and the elderly.
They need dietary supplements to provide the increased need of the body for the 20th element, to avoid developmental pathologies. Calcium-phosphorus metabolism regulates "Calcium D3". "D3" in the name of the product indicates the presence of vitamin D in it. It is rare, but necessary for full absorption calcium.
Instruction to "Calcium nycomed3" indicates that the drug belongs to pharmaceutical formulations of combined action. The same is said about calcium chloride. It not only replenishes the deficiency of the 20th element, but also saves from intoxication, and is also able to replace blood plasma. In some pathological conditions, this may be necessary.
In pharmacies, the drug " Calcium is an acid ascorbic". Such a duet is prescribed during pregnancy, during breastfeeding. Teenagers also need a supplement.
Extraction of calcium
calcium in foods, minerals, compounds, known to mankind since ancient times. In its pure form, the metal was isolated only in 1808. Luck favored Humphrey Davy. An English physicist extracted calcium by electrolysis of the element's molten salts. This method is still used today.
However, industrialists more often resort to the second method, discovered after Humphrey's research. Calcium is reduced from its oxide. The reaction is started with powder, sometimes,. The interaction takes place under vacuum conditions at elevated temperatures. For the first time, calcium was isolated in this way in the middle of the last century, in the USA.
The price of calcium
There are few manufacturers of metallic calcium. So, in Russia, the Chapetsky Mechanical Plant is mainly engaged in deliveries. It is located in Udmurtia. The company trades in granules, shavings and lumps of metal. The price tag for a ton of raw materials is around $1,500.
The product is also offered by some chemical laboratories, for example, the Russian Chemist society. Last, offers a 100-gram calcium. Reviews testify that it is a powder under oil. The cost of one package is 320 rubles.
In addition to offers to buy real calcium, business plans for its production are also sold on the Internet. For about 70 pages of theoretical calculations, they ask for about 200 rubles. Most of the plans were drawn up in 2015, that is, they have not lost their relevance yet.
