Among all the elements of the periodic system, several can be distinguished without which various diseases in living organisms do not just develop, but it is generally impossible to live and grow normally. One of these is calcium.
It is interesting that when it comes to this metal, as a simple substance, it does not have any benefit for a person, even harm. However, it is only worth mentioning the Ca 2+ ions , as immediately there are a lot of points characterizing their importance.
The position of calcium in the periodic system
The characteristic of calcium, like any other element, begins with an indication of its position in the periodic system. After all, it gives you the opportunity to learn a lot about this atom:
- core charge;
- the number of electrons and protons, neutrons;
- oxidation state, higher and lower;
- electronic configuration and other important things.
The element we are considering is located in the fourth large period of the second group, the main subgroup and has a serial number 20. Also, the periodic table shows the atomic weight of calcium - 40.08, which is the average value of the existing isotopes of this atom.
The degree of oxidation is one, always constant, equal to +2. Formula of higher CaO oxide . The Latin name for the element is calcium, hence the symbol of the Ca atom.
Characterization of calcium as a simple substance
Under normal conditions, this element is a metal, silver-white. The formula of calcium as a simple substance is Ca. Due to its high chemical activity, it is able to form many compounds belonging to different classes.
In the solid state of aggregation, it is not part of the human body, therefore it is of importance 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 group of alkaline earth, since when dissolved in water it gives alkali, but in nature it occurs in the form of multiple minerals and salts. A lot of calcium (400 mg / l) is included in the composition of sea water.
Crystal cell
The characteristic of calcium is explained by the structure of the crystal lattice, which it can have two types (since there is an alpha and beta form):
- cubic face-centric;
- body-centric.
The type of bond in the molecule is metallic, at the sites of the lattice, like all metals, are atom-ions.
Being in nature
There are several basic substances in nature that contain this element.
- Sea water.
- Rocks and minerals.
- Living organisms (shells and shells, bone tissue and so on).
- Groundwater in the earth's crust.
The following types of rocks and minerals, which are natural sources of calcium, can be identified.
- Dolomite is a mixture of calcium carbonate and magnesium.
- Fluorite is calcium fluoride.
- Gypsum - CaSO 4 · 2H 2 O.
- Calcite - chalk, limestone, marble - calcium carbonate.
- Alabaster - CaSO 4 · 0.5H 2 O.
- Apatity.
In total, about 350 different minerals and rocks that contain calcium are isolated.
Production methods
For a long time, it was not possible to isolate the metal in its free form, since its chemical activity is high; you cannot meet it in its pure form. Therefore, up to the 19th century (1808), the element in question was another mystery carried by the periodic table.
Calcium as a metal was able to synthesize the English chemist Humphry Davy. It was he who first discovered the features of the interaction of melts of solid minerals and salts with electric current. To date, the most relevant way to obtain this metal is still 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 the aluminothermy method common in metallurgy.
Physical properties
The physical characteristics of calcium can be described in several ways.
- The state of aggregation is solid under ordinary conditions.
- Melting point - 842 0 C.
- The metal is soft, can be cut with a knife.
- Color - silver-white, brilliant.
- It has good conductive and thermally conductive properties.
- With prolonged heating, it passes into a liquid, then vaporous state, losing its metallic properties. Boiling point 1484 0 .
The physical properties of calcium have one feature. When pressure is exerted on a metal, then at some point in time it loses its metallic properties and ability to conductivity. However, with a further increase in exposure, it is again restored and manifests itself as a superconductor, several times higher than the other elements in terms of these indicators.
Chemical properties
The activity of this metal is very high. Therefore, there are many interactions in which calcium enters. Reactions with all non-metals are commonplace for him, because as a reducing agent he is very strong.
- Under normal conditions, it easily reacts with the formation of the corresponding binary compounds with: halogens, oxygen.
- When heated: hydrogen, nitrogen, carbon, silicon, phosphorus, boron, sulfur and others.
- In the open air it immediately interacts with carbon dioxide and oxygen, therefore it is covered with a gray coating.
- Reacts violently with acids, sometimes with ignition.
Interesting properties of calcium are manifested when it comes to it in the composition of salts. So, beautiful cave stalactites and stalagmites growing on the ceiling and walls are nothing more than calcium carbonate, formed over time from water, carbon dioxide and bicarbonate under the influence of processes inside groundwater.
Given how active the metal is in its normal state, it is stored in laboratories, like alkaline. In a dark glass dish with a tightly closed lid and under a layer of kerosene or paraffin.
A qualitative reaction to calcium ion is the color of the flame in a beautiful, saturated brick red color. It is also possible to identify a metal in the composition of compounds by the insoluble precipitation of some of its salts (calcium carbonate, fluoride, sulfate, phosphate, silicate, sulfite).
Metal compounds
The types of metal compounds are as follows:
- oxide;
- hydroxide;
- calcium salts (medium, acidic, basic, double, complex).
Calcium oxide is known as quicklime. CaO is used to create building material (lime). If you quench the oxide with water, you will get the corresponding hydroxide, showing the properties of alkali.
Of great practical importance are precisely the various calcium salts that are used in various sectors of the economy. What kind of salts exist, we have already mentioned above. We give examples of the types of these compounds.
- The middle salts are CaCO 3 carbonate, Ca 3 (PO 4 ) 2 phosphate and others.
- Acidic - CaHSO 4 hydrosulfate.
- The main ones are hydrocarbonate (CaOH) 3 PO 4 .
- Complex - [Ca (NH 3 ) 8 ] Cl 2.
- 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
What is important calcium for the human body? There are several reasons.
- It is the ions of this element that are part of the intercellular substance and tissue fluid, participating in the regulation of mechanisms of excitation, the production of hormones and neurotransmitters.
- Calcium accumulates in the bones, 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.
- Blood coagulability also depends on the ions in question.
- It is part of the heart muscle, participating in its excitation and contraction.
- It is a participant in the processes of exocytosis and other intracellular changes.
If the amount of calcium consumed is not enough, then the development of diseases such as:
- rickets;
- osteoporosis;
- blood diseases.
The daily norm for an adult is 1000 mg, and for children from 9 years old 1300 mg. In order to prevent an excess of this element in the body, one should not exceed the specified dose. Otherwise, intestinal diseases may develop.
For all other living things, calcium is equally important. For example, many invertebrate animals, although they do not have a skeleton, however, external means of strengthening them are also formations of this metal. Among them:
- mollusks;
- mussels and oysters;
- sponges;
- coral polyps.
All of them carry on their backs or, in principle, form a certain external skeleton in the process of life, protecting them from external influences and predators. Its main component is calcium salts.
Vertebrate animals, like humans, need the ions in question for normal growth and development and receive them with food.
Calcium-containing preparations
There are many options by which it is possible to make up for the missing norm of an element in the body. Best of all, of course, are natural methods - products containing the right atom. However, if for some reason this is insufficient or impossible, the medical path is also acceptable.
So, the list of foods containing calcium is something like this:
- dairy and sour-milk products;
- fish;
- greens;
- cereals (buckwheat, rice, pastries from whole grain flour);
- some citrus fruits (oranges, tangerines);
- legumes;
- whole nuts (especially almonds and walnuts).
If you are allergic to certain products or you cannot use them for another reason, then calcium-containing preparations will help to fill the level of the desired 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.
- Calcium Chloride - a 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", because it causes just such a feeling when injected. There are forms with fruit juice to facilitate oral administration.
- Calcium gluconate. Available in tablets (0.25 or 0.5 g), and solutions for intravenous injection. Often in the form of tablets contains various fruit additives.
- Calcium Lactate - Available in 0.5 g tablets.