Calcium compounds in nature. "calcium and its compounds


Calcium compounds.

Sao– calcium oxide or quicklime, obtained by the decomposition of limestone: CaCO 3 = CaO + CO 2 is an oxide of an alkaline earth metal, so it actively interacts with water: CaO + H 2 O = Ca (OH) 2

Ca(OH) 2 – calcium hydroxide or slaked lime, therefore the reaction CaO + H 2 O = Ca(OH) 2 is called slaking of lime. If the solution is filtered, the result is lime water - this is an alkali solution, so it changes the color of phenolphthalein to crimson.

Slaked lime is widely used in construction. Its mixture with sand and water is a good binding material. Under the influence of carbon dioxide, the mixture hardens Ca(OH) 2 + CO 2 = CaCO3 + H 2 O.

At the same time, part of the sand and mixture turns into silicate Ca(OH) 2 + SiO 2 = CaSiO 3 + H 2 O.

The equations Ca (OH) 2 + CO 2 = CaCO 2 + H 2 O and CaCO 3 + H 2 O + CO 2 = Ca (HCO 3) 2 play a large role in nature and in shaping the appearance of our planet. Carbon dioxide in the form of a sculptor and architect creates underground palaces in the strata of carbonate rocks. It is capable of moving hundreds and thousands of tons of limestone underground. Through cracks in rocks, water containing carbon dioxide dissolved in it enters the limestone layer, forming cavities - caster caves. Calcium bicarbonate exists only in solution. Groundwater moves in the earth's crust, evaporating water under suitable conditions: Ca(HCO3) 2 = CaCO3 + H2O + CO 2 , This is how stalactites and stalagmites are formed, the formation scheme of which was proposed by the famous geochemist A.E. Fersman. There are a lot of castrum caves in Crimea. Science studies them speleology.

Calcium carbonate used in construction CaCO3- chalk, limestone, marble. You have all seen our railway station: it is decorated with white marble brought from abroad.

experience: blow through a tube into a solution of lime water, it becomes cloudy .

Ca(OH) 2 + CO 2 = CaCO 3 + N 2 ABOUT

Acetic acid is added to the formed precipitate, boiling is observed, because carbon dioxide is released.

CaCO 3 +2CH 3 COOH = Ca(CH 3 SOO) 2 +H 2 O + CO 2

THE TALE OF THE CARBONATE BROTHERS.

Three brothers live on earth
From the Carbonate family.
The older brother is a handsome MARBLE,
Glorious in the name of Karara,
An excellent architect. He
Built Rome and the Parthenon.
Everyone knows LIMESTONE,
That's why it's named like that.
Famous for his work
Building a house behind the house.
Both capable and able
Little soft brother MEL.
Look how he draws,
This CaCO 3!
Brothers love to frolic
Heat in a hot oven,
CaO and CO 2 are then formed.
This is carbon dioxide
Each of you is familiar with him,
We exhale it.
Well, this is SaO -
Hot-burnt quicklime.
Add water to it,
Mix thoroughly
So that there is no trouble,
We protect our hands
Well-kneaded LIME, but SLASHED!
Lime milk
The walls are whitewashed easily.
The bright house became cheerful,
Turning lime into chalk.
Hocus Pocus for the People:
You just have to blow through the water,
How easy it is
Turned into milk!
And now it's pretty clever
I get soda:
Milk plus vinegar. Ay!
Foam is pouring over the edge!
Everything is in worries, everything is in work
From dawn to dawn -
These brothers Carbonates,
These CaCO 3!

Repetition: CaO– calcium oxide, quicklime;
Ca(OH) 2 – calcium hydroxide (slaked lime, lime water, milk of lime depending on the concentration of the solution).
The general thing is the same chemical formula Ca(OH) 2. Difference: lime water is a transparent saturated solution of Ca(OH) 2, and milk of lime is a white suspension of Ca(OH) 2 in water.
CaCl 2 - calcium chloride, calcium chloride;
CaCO 3 – calcium carbonate, chalk, shell marble, limestone.
L/R: collections. Next, we demonstrate a collection of minerals available in the school laboratory: limestone, chalk, marble, shell rock.
CaS0 4 ∙ 2H 2 0 - calcium sulfate crystal hydrate, gypsum;
CaCO 3 - calcite, calcium carbonate is part of many minerals that cover 30 million km 2 on earth.

The most important of these minerals is limestone. Shell rocks, limestones of organic origin. It is used in the production of cement, calcium carbide, soda, all types of lime, and in metallurgy. Limestone is the basis of the construction industry; many building materials are made from it.

Chalk It's not just tooth powder and school chalk. It is also a valuable additive in the production of paper (coated - top quality) and rubber; in construction and renovation of buildings - as whitewash.

Marble is a dense crystalline rock. There is a colored one - white, but most often various impurities color it in different colors. Pure white marble is rare and is mainly used by sculptors (statues by Michelangelo, Rodin. In construction, colored marble is used as a facing material (Moscow Metro) or even as the main building material of palaces (Taj Mahal).

In the world of interesting things “Taj Mahal MAUSOLEUM”

Shah Jahan of the Great Mughal dynasty kept almost all of Asia in fear and obedience. In 1629, Mumzat Mahal, Shah Jahan's beloved wife, died at the age of 39 during childbirth on a campaign (this was their 14th child, all of them boys). She was unusually beautiful, bright, smart, the emperor obeyed her in everything. Before her death, she asked her husband to build a tomb, take care of the children, and not marry. The saddened king sent his envoys to all the big cities, the capitals of neighboring states - to Bukhara, Samarkand, Baghdad, Damascus, to find and invite the best craftsmen - in memory of his wife, the king decided to erect the best building in the world. At the same time, messengers sent plans for all the best buildings in Asia and the best building materials to Agra (India). They even brought malachite from Russia and the Urals. The chief masons came from Delhi and Kandahar; architects - from Istanbul, Samarkand; decorators - from Bukhara; gardeners - from Bengal; the artists were from Damascus and Baghdad, and the well-known master Ustad-Isa was in charge.

Together, over 25 years, a chalk marble structure was built surrounded by green gardens, blue fountains and a red sandstone mosque. 20,000 slaves erected this miracle of 75 m (25-story building). Nearby I wanted to build a second mausoleum of black marble for myself, but I didn’t have time. He was overthrown from the throne by his own son (the 2nd, and he also killed all his brothers).

The ruler and master of Agra spent the last years of his life looking out of the narrow window of his prison. For 7 years my father admired his creation. When the father went blind, the son made him a system of mirrors so that the father could admire the mausoleum. He was buried in the Taj Mahal, next to his Mumtaz.

Those entering the mausoleum see cenotaphs - false tombs. The eternal resting places of the Great Khan and his wife are located downstairs in the basement. Everything there is encrusted with precious stones that glow as if they were alive, and the branches of fairy-tale trees, intertwined with flowers, adorn the walls of the tomb in intricate patterns. Crafted by the best carvers, turquoise-blue lapis lazuli, green-black jades and red amethysts celebrate the love of Shah Jahal and Mumzat Mahal.

Every day tourists rush to Agra, wanting to see the true wonder of the world - the Taj Mahal mausoleum, as if floating above the ground.

CaCO 3 is a building material for the exoskeleton of mollusks, corals, shells, etc., and egg shells. (illustrations or Animals of the coral biocenosis” and display of a collection of sea corals, sponges, shell rock).

Among all the elements of the periodic table, several can be identified, without which not only do various diseases develop in living organisms, but it is generally impossible to live and grow normally. One of these is calcium.

It is interesting that when we talk about this metal as a simple substance, it has no benefit for humans, even harm. However, as soon as you mention Ca 2+ ions, a lot of points immediately arise that characterize their importance.

Position of calcium in the periodic table

The characterization of calcium, like any other element, begins with indicating its location in the periodic table. After all, it makes it possible to learn a lot about a given atom:

  • nuclear charge;
  • number of electrons and protons, neutrons;
  • oxidation state, highest and lowest;
  • electronic configuration and other important things.

The element we are considering is located in the fourth major period of the second group, the main subgroup, and has a serial number of 20. Also, the periodic chemical table shows the atomic weight of calcium - 40.08, which is the average value of the existing isotopes of a given atom.

The oxidation state is one, always constant, equal to +2. Formula CaO. The Latin name for the element is calcium, hence the symbol for the Ca atom.

Characteristics of calcium as a simple substance

Under normal conditions, this element is a metal, silvery-white in color. The formula of calcium as a simple substance is Ca. Due to its high chemical activity, it is capable of forming many compounds belonging to different classes.

In a solid state of aggregation, it is not part of the human body, therefore it is important for industrial and technical needs (mainly chemical syntheses).

It is one of the most common metals in the earth’s crust, about 1.5%. It belongs to the alkaline earth group, since when dissolved in water it produces alkalis, but in nature it is found in the form of multiple minerals and salts. A lot of calcium (400 mg/l) is included in sea water.

Crystal cell

The characteristics of calcium are explained by the structure of the crystal lattice, which can be of two types (since there is an alpha and beta form):

  • cubic face-centric;
  • volume-centric.

The type of bond in the molecule is metallic; at lattice sites, like all metals, there are atom ions.

Being in nature

There are several main substances in nature that contain this element.

  1. Sea water.
  2. Rocks and minerals.
  3. Living organisms (shells and shells, bone tissue, etc.).
  4. Groundwater in the earth's crust.

The following types of rocks and minerals can be identified as natural sources of calcium.

  1. Dolomite is a mixture of calcium and magnesium carbonate.
  2. Fluorite is calcium fluoride.
  3. Gypsum - CaSO 4 2H 2 O.
  4. Calcite - chalk, limestone, marble - calcium carbonate.
  5. Alabaster - CaSO 4 ·0.5H 2 O.
  6. Apatity.

In total, there are about 350 different minerals and rocks that contain calcium.

Methods of obtaining

For a long time it was not possible to isolate the metal in its free form, since its chemical activity is high and cannot be found in nature in its pure form. Therefore, until the 19th century (1808), the element in question was another mystery posed by the periodic table.

The English chemist Humphry Davy managed to synthesize calcium as a metal. It was he who first discovered the peculiarities of the interaction of melts of solid minerals and salts with electric current. Today, the most relevant way to obtain this metal is the electrolysis of its salts, such as:

  • a mixture of calcium and potassium chlorides;
  • a mixture of fluoride and calcium chloride.

It is also possible to extract calcium from its oxide using aluminothermy, a common method in metallurgy.

Physical properties

The characteristics of calcium according to physical parameters can be described in several points.

  1. The state of aggregation is solid under normal conditions.
  2. Melting point - 842 0 C.
  3. The metal is soft and can be cut with a knife.
  4. Color - silver-white, shiny.
  5. It has good conductive and heat-conducting properties.
  6. When heated for a long time, it turns into a liquid, then a vapor state, losing its metallic properties. Boiling point 1484 0 C.

The physical properties of calcium have one peculiarity. When pressure is applied to a metal, at some point in time it loses its metallic properties and ability to conduct electrically. However, with a further increase in exposure, it is restored again and manifests itself as a superconductor, several times higher in these indicators than other elements.

Chemical properties

The activity of this metal is very high. Therefore, there are many interactions that calcium enters into. Reactions with all non-metals are common for him, because as a reducing agent he is very strong.

  1. Under normal conditions, it easily reacts to form the corresponding binary compounds with: halogens, oxygen.
  2. When heated: hydrogen, nitrogen, carbon, silicon, phosphorus, boron, sulfur and others.
  3. In the open air it immediately interacts with carbon dioxide and oxygen, and therefore becomes covered with a gray coating.
  4. Reacts violently with acids, sometimes causing inflammation.

Interesting properties of calcium appear when it comes to salts. So, beautiful caves growing on the ceiling and walls are nothing more than formed over time from water, carbon dioxide and bicarbonate under the influence of processes within underground waters.

Considering how active the metal is in its normal state, it is stored in laboratories, just like alkaline metals. In a dark glass container, with a tightly closed lid and under a layer of kerosene or paraffin.

A qualitative reaction to calcium ion is the coloring of the flame in a beautiful, rich brick-red color. You can also identify the metal in the composition of the compounds by the insoluble precipitates of some of its salts (calcium carbonate, fluoride, sulfate, phosphate, silicate, sulfite).

Metal connections

The types of metal compounds are as follows:

  • oxide;
  • hydroxide;
  • calcium salts (medium, acidic, basic, double, complex).

Calcium oxide known as CaO is used to create a building material (lime). If you quench the oxide with water, you get the corresponding hydroxide, which exhibits the properties of an alkali.

Various calcium salts, which are used in different sectors of the economy, are of great practical importance. We have already mentioned above what kind of salts exist. Let us give examples of the types of these connections.

  1. Medium salts - carbonate CaCO 3, phosphate Ca 3 (PO 4) 2 and others.
  2. Acidic - hydrogen sulfate CaHSO 4.
  3. The main ones are bicarbonate (CaOH) 3 PO 4.
  4. Complex - Cl 2.
  5. Double - 5Ca(NO 3) 2 *NH 4 NO 3 *10H 2 O.

It is in the form of compounds of this class that calcium is important for biological systems, since salts are the source of ions for the body.

Biological role

Why is calcium important for the human body? There are several reasons.

  1. It is the ions of this element that are part of the intercellular substance and tissue fluid, participating in the regulation of excitation mechanisms, the production of hormones and neurotransmitters.
  2. Calcium accumulates in bones and tooth enamel in an amount of about 2.5% of the total body weight. This is quite a lot and plays an important role in strengthening these structures, maintaining their strength and stability. The growth of the body without this is impossible.
  3. Blood clotting also depends on the ions in question.
  4. It is part of the heart muscle, participating in its excitation and contraction.
  5. It is a participant in the processes of exocytosis and other intracellular changes.

If the amount of calcium consumed is not enough, then diseases such as:

  • rickets;
  • osteoporosis;
  • blood diseases.

The daily intake for an adult is 1000 mg, and for children over 9 years old 1300 mg. In order to prevent an excess of this element in the body, you should not exceed the specified dose. Otherwise, intestinal diseases may develop.

For all other living beings, calcium is no less important. For example, although many do not have a skeleton, their external means of strengthening are also formations of this metal. Among them:

  • shellfish;
  • mussels and oysters;
  • sponges;
  • coral polyps.

They all carry on their backs or, in principle, form in the process of life a certain external skeleton that protects them from external influences and predators. Its main component is calcium salts.

Vertebrates, like humans, need these ions for normal growth and development and receive them from food.

There are many options with which it is possible to replenish the missing element in the body. The best, of course, are natural methods - products containing the desired atom. However, if for some reason this is insufficient or impossible, the medical route is also acceptable.

So, the list of foods containing calcium is something like this:

  • dairy and fermented milk products;
  • fish;
  • greenery;
  • grains (buckwheat, rice, baked goods made from whole grain flour);
  • some citrus fruits (oranges, tangerines);
  • legumes;
  • all nuts (especially almonds and walnuts).

If you are allergic to some foods or cannot eat them for another reason, then calcium-containing preparations will help replenish the level of the necessary element in the body.

All of them are salts of this metal, which have the ability to be easily absorbed by the body, quickly absorbed into the blood and intestines. Among them, the most popular and used are the following.

  1. Calcium chloride - solution for injection or for oral administration to adults and children. It differs in the concentration of salt in the composition; it is used for “hot injections”, since it causes exactly this sensation when injected. There are forms with fruit juice for easier oral administration.
  2. Available in both tablets (0.25 or 0.5 g) and solutions for intravenous injection. Often in tablet form it contains various fruit additives.
  3. Calcium lactate - available in tablets of 0.5 g.

In ancient times, people used calcium compounds for construction. Basically it was calcium carbonate found in rocks, or a product of its firing - lime. Marble and plaster were also used. Previously, scientists believed that lime, which is calcium oxide, was a simple substance. This misconception existed until the end of the 18th century, until Antoine Lavoisier expressed his assumptions about this substance.

Lime extraction

At the beginning of the 19th century, the English scientist Humphrey Davy discovered calcium in its pure form using electrolysis. Moreover, he received a calcium amalgam from slaked lime and mercury oxide. Then, having distilled off the mercury, he obtained metallic calcium.

The reaction of calcium with water occurs violently, but is not accompanied by fire. Due to the abundant release of hydrogen, the calcium plate will move through the water. A substance is also formed - calcium hydroxide. If phenolphthalein is added to a liquid, it will turn a bright crimson color - therefore, Ca(OH)₂ is a base.

Ca + 2H₂O → Ca(OH)₂↓ + H₂

Reaction of calcium with oxygen

The reaction of Ca and O₂ is very interesting, but the experiment cannot be performed at home, as it is very dangerous.

Let's consider the reaction of calcium with oxygen, namely the combustion of this substance in air.

Attention! Do not try to repeat this experience yourself! you'll find safe chemistry experiments you can do at home.

Let's take potassium nitrate KNO₃ as a source of oxygen. If calcium was stored in kerosene liquid, then before the experiment it must be cleaned using a burner, holding it over the flame. Next, the calcium is dipped into KNO₃ powder. Then the calcium with potassium nitrate must be placed in the flame of the burner. The decomposition reaction of potassium nitrate into potassium nitrite and oxygen occurs. The released oxygen ignites the calcium, and the flame turns red.

KNO₃ → KNO₂ + O₂

2Ca + O₂ → 2CaO

It is worth noting that calcium reacts with some elements only when heated, these include: sulfur, boron, nitrogen and others.

Calcium- element of the 4th period and PA group of the Periodic Table, serial number 20. Electronic formula of the atom [ 18 Ar]4s 2, oxidation states +2 and 0. Refers to alkaline earth metals. It has low electronegativity (1.04) and exhibits metallic (basic) properties. Forms (as a cation) numerous salts and binary compounds. Many calcium salts are slightly soluble in water. In nature - sixth In terms of chemical abundance, the element (third among metals) is found in a bound form. A vital element for all organisms. The lack of calcium in the soil is compensated by applying lime fertilizers (CaC0 3, CaO, calcium cyanamide CaCN 2, etc.). Calcium, calcium cation and its compounds color the flame of a gas burner dark orange ( qualitative detection).

Calcium Ca

Silvery-white metal, soft, ductile. In humid air it fades 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 - calciumthermia):

Receipt calcium in industry:

Calcium is used to remove non-metal impurities from metal alloys, as a component of light and anti-friction alloys, and to separate rare metals from their oxides.

Calcium oxide CaO

Basic oxide. Technical name: quicklime. White, very hygroscopic. It has an ionic structure Ca 2+ O 2- . Refractory, thermally stable, volatile when ignited. Absorbs moisture and carbon dioxide from the air. Reacts vigorously with water (with high exo- effect), forms a strongly alkaline solution (a hydroxide precipitate is possible), a process 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, and a component of binding materials in construction.

Equations of the most important reactions:

Receipt Sao in industry— limestone firing (900-1200 °C):

CaCO3 = CaO + CO2

Calcium hydroxide Ca(OH) 2

Basic hydroxide. Technical name is slaked lime. White, hygroscopic. It has an ionic structure: Ca 2+ (OH -) 2. Decomposes when heated moderately. Absorbs moisture and carbon dioxide from the air. Slightly soluble in cold water (an alkaline solution is formed), and even less soluble in boiling water. A clear solution (lime water) quickly becomes cloudy due to the precipitation of hydroxide precipitate (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 CaCO 3 precipitate 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 preparing lime mortars - dough-like mixtures (sand + slaked lime + water), serving as a binding material for stone and brickwork, finishing ( plastering) walls and other construction purposes. The hardening (“setting”) of such solutions is due to the absorption of carbon dioxide from the air.

History of calcium

Calcium was discovered in 1808 by Humphry Davy, who, by electrolysis of slaked lime and mercuric oxide, obtained calcium amalgam, as a result of the process of distilling mercury from which the metal remained, called calcium. In Latin lime sounds like calx, it was this name that was chosen by the English chemist for the discovered substance.

Calcium is an element of the main subgroup II of group IV of the periodic table of chemical elements D.I. Mendeleev, has an atomic number of 20 and an atomic mass of 40.08. The accepted designation is Ca (from the Latin - Calcium).

Physical and chemical properties

Calcium is a reactive soft alkali metal with a silvery-white color. Due to interaction with oxygen and carbon dioxide, the surface of the metal becomes dull, so calcium requires a special storage regime - a tightly closed container, in which the metal is filled with a layer of liquid paraffin or kerosene.

Calcium is the most well-known of the microelements necessary for humans; the daily requirement for it ranges from 700 to 1500 mg for a healthy adult, but it increases during pregnancy and lactation; this must be taken into account and calcium must be obtained in the form of preparations.

Being in nature

Calcium has very high chemical activity, therefore it is not found in nature in its free (pure) form. However, it is the fifth most common in the earth's crust; it is found in the form of compounds in sedimentary (limestone, chalk) and rocks (granite); feldspar anorite contains a lot of calcium.

It is quite widespread in living organisms; its presence has been found in plants, animals and humans, where it is present mainly in teeth and bone tissue.

Calcium absorption

An obstacle to the normal absorption of calcium from food is the consumption of carbohydrates in the form of sweets and alkalis, which neutralize the hydrochloric acid of the stomach, which is necessary to dissolve calcium. The process of calcium absorption is quite complex, so sometimes it is not enough to get it only from food; additional intake of the microelement is necessary.

Interaction with others

To improve the absorption of calcium in the intestine, it is necessary, which tends to facilitate the process of calcium absorption. When taking calcium (in the form of supplements) while eating, absorption is blocked, but taking calcium supplements separately from food does not affect this process in any way.

Almost all of the body's calcium (1 to 1.5 kg) is found in bones and teeth. Calcium is involved in the processes of excitability of nervous tissue, muscle contractility, blood clotting processes, is part of the nucleus and membranes of cells, cellular and tissue fluids, has anti-allergic and anti-inflammatory effects, prevents acidosis, and activates a number of enzymes and hormones. Calcium is also involved in the regulation of cell membrane permeability and has the opposite effect.

Signs of calcium deficiency

Signs of calcium deficiency in the body are the following, at first glance, unrelated symptoms:

  • nervousness, worsening mood;
  • cardiopalmus;
  • convulsions, numbness of extremities;
  • slowing of growth and children;
  • high blood pressure;
  • splitting and brittleness of nails;
  • joint pain, lowering the “pain threshold”;
  • heavy menstruation.

Causes of calcium deficiency

Causes of calcium deficiency include unbalanced diets (especially fasting), low calcium content in food, smoking and addiction to coffee and caffeine-containing drinks, dysbacteriosis, kidney disease, thyroid disease, pregnancy, lactation and menopause.

Excess calcium, which can occur with excessive consumption of dairy products or uncontrolled use of drugs, is characterized by extreme thirst, nausea, vomiting, loss of appetite, weakness and increased urination.

Uses of calcium in life

Calcium has found application in the metallothermic production of uranium, in the form of natural compounds it is used as a raw material for the production of gypsum and cement, as a means of disinfection (well-known bleach).