Among all the elements of the periodic system, there are several of them, without which it is not only possible to develop various diseases in living organisms, 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, one has only to mention the ions Ca2+, as immediately there is a mass of points characterizing their importance.
Position of calcium in the Periodic Table
Characterization of calcium, like any other element, begins with an indication of its position in the periodic system. After all, it makes it possible to learn a lot about this atom:
- core charge;
- 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 serial number 20. Also, the chemical periodic table shows the atomic weight of calcium - 40.08, which is the average value of the existing isotopes of thisatom.
The oxidation state is one, always constant, equal to +2. The formula of the higher oxide CaO. The Latin name for the element is calcium, hence the symbol for the atom Ca.
Characterization of calcium as a simple substance
Under normal conditions, this element is a metal, silvery 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 important for industrial and technical needs (mainly chemical syntheses).
Is one of the most common metals in terms of the share in the earth's crust, about 1.5%. It belongs to the group of alkaline earths, since when dissolved in water it gives alkalis, but in nature it occurs in the form of multiple minerals and s alts. A lot of calcium (400 mg/l) is included in sea water.
Crystal lattice
The characteristic of calcium is explained by the structure of the crystal lattice, which can be of two types (since there is an alpha and a beta form):
- cubic face-centric;
- volume centric.
The type of bond in the molecule is metallic, at the lattice sites, like all metals, there 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 andshells, bone tissue, and so on).
- Groundwater in the earth's crust.
The following types of rocks and minerals can be identified as natural sources of calcium.
- Dolomite is a mixture of calcium and magnesium carbonate.
- Fluorite - calcium fluoride.
- Gypsum - CaSO4 2H2O.
- Calcite - chalk, limestone, marble - calcium carbonate.
- Alabaster - CaSO4 0.5H2O.
- Apatity.
In total, there are about 350 different minerals and rocks that contain calcium.
Methods of obtaining
It was not possible to isolate the metal in free form for a long time, since its chemical activity is high, you will not find it in pure form in nature. Therefore, until the 19th century (1808), the element in question was another mystery that the periodic table carried.
Calcium as a metal was able to synthesize the English chemist Humphrey Davy. It was he who first discovered the features of the interaction of melts of solid minerals and s alts with electric current. To date, still the most relevant way to obtain this metal is the electrolysis of its s alts, such as:
- a mixture of calcium and potassium chlorides;
- mixture of fluoride and calcium chloride.
It is also possible to extract calcium from its oxide using the aluminothermic method common in metallurgy.
Physical properties
Characterization of calcium in terms of physical parameters can be described in several points.
- The aggregate state is solid under normal conditions.
- Melting point - 842 0C.
- Metal is soft, can be cut with a knife.
- Color - silvery white, shiny.
- It has good conductive and thermal properties.
- When heated for a long time, it turns into a liquid, then a vapor state, losing its metallic properties. Boiling point 1484 0C.
The physical properties of calcium have one feature. When pressure is applied to a metal, at some point in time it loses its metallic properties and ability to conduct electricity. However, with a further increase in exposure, it is restored again and manifests itself as a superconductor, several times higher than the rest of the elements in 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 common for him, because as a reducing agent he is very strong.
- Under normal conditions easily reacts to form 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 becomes covered with a gray coating.
- Reacts violently with acids, sometimes flammable.
Interesting properties of calcium appear when it comes toabout it in the composition of s alts. So, the beautiful cave stalactites and stalagmites that grow 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 ones. In a dark glass container with a tightly closed lid and under a layer of kerosene or paraffin.
Qualitative reaction to the calcium ion is the color of the flame in a beautiful, rich brick-red color. It is also possible to identify a metal in the composition of compounds by insoluble precipitates of some of its s alts (calcium carbonate, fluoride, sulfate, phosphate, silicate, sulfite).
Metal joints
The types of metal compounds are as follows:
- oxide;
- hydroxide;
- calcium s alts (medium, acidic, basic, double, complex).
Calcium oxide is known as quicklime. CaO is used to create a building material (lime). If you extinguish the oxide with water, you get the corresponding hydroxide, which exhibits the properties of alkali.
Various calcium s alts, which are used in various sectors of the economy, are of great practical importance. What kind of s alts exist, we have already mentioned above. Here are examples of the types of these compounds.
- Medium s alts - carbonate CaCO3, phosphate Ca3(PO4) 2 and others.
- Acidic - hydrosulfate CaHSO4.
- Basic - bicarbonate(SaOH)3PO4.
- Complex - [Ca (NH3)8] Cl2.
- Double - 5Ca(NO3)2NH4NO 310H2O.
It is in the form of compounds of this class that calcium is important for biological systems, since s alts are the source of ions for the body.
Biological role
What is the importance of 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 the 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 it is impossible.
- Blood clotting also depends on the ions in question.
- It is part of the heart muscle, participating in its excitation and contraction.
- 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 overabundance of this element in the body, the indicated dose should not be exceeded. Otherwisecase, bowel disease may develop.
For all other living beings, calcium is no less important. For example, many invertebrates, although they do not have a skeleton, however, external means of strengthening them are also formations of this metal. Among them:
- shellfish;
- mussels and oysters;
- sponges;
- coral polyps.
All of them carry on their backs or, in principle, form in the process of life some kind of external skeleton that protects them from external influences and predators. Its main component is calcium s alts.
Vertebrates, like humans, need these ions for normal growth and development and get them from food.
Calcium-containing preparations
There are many options by which it is possible to make up for the missing element in the body. Best of all, of course, natural methods - products containing the desired 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, whole grain pastries);
- some citrus fruits (oranges, tangerines);
- legumes;
- all nuts (especially almonds and walnuts).
If you are allergic to some products or you can’t use them for another reason, then replenish the level of the desired element in the bodycalcium containing preparations will help.
All of them are s alts of this metal, which have the ability to be easily absorbed by the body, quickly absorbed into the blood and intestines. Among them, the following are the most popular and used.
- Calcium chloride - solution for injection or oral administration to adults and children. It differs in the concentration of s alt in the composition, it is used for "hot injections", because it causes just such a sensation when injected. Fruit juice forms are available for ease of ingestion.
- Calcium gluconate. Available as 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 0.5g tablets
