Chemical element calcium belongs to the II group of periodic Mendeleev's system. In the nature this light silver-white metal is presented by mix of six stable isotopes.
Calcium in the nature
On the prevalence in earth crust calcium takes the fifth place, its content is 2.96% on weight. It actively migrates, collecting in various geochemical systems. About 385 minerals of calcium are known, by their quantity it takes the fourth place among all chemical elements.
Calcium prevails in the lower part of earth crust, in its Earth's mantle it is not enough. The most part of this element is a part of feldspar — the anortit. Calcium is also contained: plaster, marble and limestone, lime is a product of its roasting.
In live substance calcium — the most important of metals, exists the organisms containing more than 10% of calcium, they build the skeleton of its connections. Accumulation of limestone is connected with burials of skeletons of sea plants and animals. Plunging into depth of Earth, they are mineralized and turn into different types of marble. The rivers bring calcium to the ocean, but in water he is not late, concentrating in skeletons of organisms. After their death, calcium is besieged on a bottom.
Physical and chemical properties
At calcium face-centered cubic crystal lattice. This element is very active chemically, in connections it dvukhvalenten. At the room temperature metal easily reacts with oxygen and moisture of air, for this reason it is stored in tight the closed vessels or in mineral oils. When heating on air or in oxygen it ignites, forming calcium oxide. Reaction with cold water at first proceeds quickly, and then slows down because of formation of a film of a hydroxide of calcium. This metal vigorously interacts with acids or hot water, emitting hydrogen. With bromine and chlorine calcium enters and reaction at a temperature above 400 °C, forming bromide and chloride of calcium.
Receiving and application
In the industry calcium is received in two ways. In the first case heat to 1200 °C in a vacuum the bricketed mix of oxide of calcium and powder of aluminum, at the same time vapors of calcium are besieged on a cold surface. The second method of receiving is electrolysis of fusion of chlorides of calcium and potassium by means of the liquid copper-calcium cathode. In pure form calcium is used as reducer of rare-earth metals and their connections. It is applied to removal of sulfur from oil products, by purifications of argon of nitrogen impurity, to dehydration of organic liquids and also in electrovacuum devices as the absorber of gases.