Chemical properties of alkaline earth metals. Application of alkaline earth metals. Physical properties of alkaline earth metals

Consider the chemical properties of alkaline earth metals. Define the features of their structure, acquisition, finding in nature, application.

Position in the PS

First, we determine the location of these elements in the periodic system of Mendeleyev. They are located in the second group of the main subgroup. They include calcium, strontium, radium, barium, magnesium, beryllium. All of them at the external energy level contain two valence electrons. In general, beryllium, magnesium and alkaline earth metals have ns2 electrons at the outer level. In chemical compounds, they exhibit an oxidation state of +2. During interaction with other substances, they exhibit restorative properties, giving off electrons from the external energy level.

Edit properties

As the nucleus of the atom increases, magnesium and alkaline earth metals strengthen their metallic properties, as the radius of their atoms increases. Let us consider the physical properties of alkaline earth metals. Beryllium in its usual state is a metal of gray color with a steel luster. It has a dense hexagonal crystal lattice. Upon contact with atmospheric oxygen, beryllium immediately forms an oxide film, as a result of which its chemical activity decreases, a matt coating is formed.

Physical properties

Magnesium as a simple substance is a white metal that forms an oxide coating on the air. It has a hexagonal crystal lattice.

The physical properties of alkaline earth metals of calcium, barium, strontium are similar. They are metals with a characteristic silvery sheen, which are covered with yellowish film under the influence of oxygen in the air. In calcium and strontium, a cubic face-centered lattice, barium has a body-centered structure.

Chemistry of alkaline earth metals is based on the fact that they have a metallic character of the bond. That is why they are distinguished by high electrical and heat conductivity. The temperatures of their melting and boiling are greater than those of alkali metals.

Methods of obtaining

The production of beryllium in industrial quantities is carried out by reducing the metal from fluoride. The condition for this chemical reaction is preheating.

Given that the alkaline earth metals in nature are in the form of compounds, for the production of magnesium, strontium, calcium electrolysis of melts of their salts.

Chemical properties

The chemical properties of alkaline earth metals are associated with the need for preliminary removal of an oxide film layer from their surface. It is she who determines the inertness of these metals to water. Calcium, barium, strontium upon dissolution in water form hydroxides, which have pronounced basic properties.

The chemical properties of alkaline earth metals suggest their interaction with oxygen. For the barium the product of the interaction is peroxide, for all the rest after the reaction oxides are formed. In all the representatives of this class oxides exhibit basic properties, only for beryllium oxide amphoteric properties are characteristic.

The chemical properties of alkaline earth metals are also manifested in the reaction with sulfur, halogens, and nitrogen. In reactions with acids, dissolution of these elements is observed. Given that beryllium refers to amphoteric elements, it is able to react chemically with alkali solutions.

Qualitative reactions

The basic formulas of alkaline earth metals considered in the course of inorganic chemistry are associated with salts. To identify representatives of this class in a mixture with other elements, you can use a qualitative definition. When the salts of alkaline earth metals are introduced into the flame of the alcohol lamp, the coloration of the flame by cations is observed. The strontium cation gives a dark red shade, the calcium cation is orange, and the barium cation is a green tone.

To determine the barium cation in the qualitative analysis, sulfate anions are used. As a result of this reaction, white barium sulphate is formed, which is insoluble in inorganic acids.

Radium is a radioactive element, which in nature is contained in small quantities. When magnesium reacts with oxygen, a dazzling flash is observed. This process was used for some time during photography in dark rooms. Now the magnesium outbreaks have been replaced by electrical systems. Beryllium belongs to the family of alkaline earth metals, which reacts with many chemical substances. Calcium and magnesium are similar to aluminum, they can repair rare metals such as titanium, tungsten, molybdenum, niobium. These methods of producing metals are called calciothermia and magnesium.

Application Features

What is the use of alkaline earth metals? Calcium and magnesium are used to make light alloys and rare metals.

For example, magnesium is contained in duraluminium, and calcium is a component of lead alloys used to produce cable sheaths and bearings. Widely used alkaline earth metals in engineering in the form of oxides. Unexpired lime (calcium oxide) and burnt magnesium (magnesium oxide) are required for the construction sector.

When an interaction with calcium oxide water occurs, a significant amount of heat is released. Slaked lime (calcium hydroxide) is used for construction. A white slurry of this substance (lime milk) is used in the sugar industry for the process of cleaning beet juice.

Metal salts of the second group

The salts of magnesium, beryllium, alkaline earth metals can be obtained by interacting with the acids of their oxides. Chlorides, fluorides, iodides of these elements are white crystalline substances, mostly readily soluble in water. Among sulfates only magnesium and beryllium compounds have solubility. There is a decrease from beryllium salts to barium sulphates. Carbonates are practically insoluble in water or have minimal solubility.

Sulphides of alkaline earth elements in small amounts are contained in heavy metals. If you send lighting to them, you can get different colors. Sulphides are included in the composition of luminous compounds, called phosphors. Apply these colors to create glowing dials, road signs.

Common alkaline earth metal compounds

Calcium carbonate is the most common element on the earth's surface. It is an integral part of such compounds as limestone, marble, chalk. Among them, limestone is the main application. This mineral is indispensable in construction, it is considered an excellent building stone. In addition, from this inorganic compound, quicklime and slaked lime, glass, and cement are produced.

The use of calcareous crushed stone helps to strengthen roads, and thanks to powder, soil acidity can be reduced. Natural chalk is a shell of the oldest animals. This compound is used for the production of rubber, paper, the creation of school crayons.

Marble is in demand among architects, sculptors. It was from the marble that many unique creations of Michelangelo were created. Part of the Moscow metro stations are tiled with marble tiles. Magnesium carbonate in large volumes is used in the manufacture of bricks, cement, glass. It is needed in the metallurgical industry to remove waste rock.

Calcium sulphate, contained in nature in the form of gypsum (calcium sulphate crystal hydrate), is used in the construction industry. In medicine, this compound is used to make casts, as well as to create plaster casts.

Alabaster (semi-aquatic gypsum) during the interaction with water generates a huge amount of heat. This is also used in industry.

The English salt (magnesium sulfate) is used in medicine as a laxative. This substance has a bitter taste, it is found in seawater.

"Barite porridge" (barium sulfate) does not dissolve in water. That is why this salt is used in X-ray diagnostics. Salt delays X-rays, which allows you to identify diseases of the gastrointestinal tract.

In the composition of phosphorites (rock) and apatites there is calcium phosphate. They are needed for the preparation of calcium compounds: oxides, hydroxides.

Calcium plays a special role for living organisms. It is this metal that is necessary for the construction of the skeleton. Calcium ions are necessary to regulate the work of the heart, increase blood coagulability. The lack of it causes disturbances in the work of the nervous system, the loss of coagulation, the loss of the ability of the hands to normally hold various objects.

In order to avoid health problems, a person should consume about 1.5 grams of calcium every day. The main problem is that in order for the body to absorb 0.06 grams of calcium, one must eat 1 gram of fat. The maximum amount of this metal is contained in salad, parsley, cottage cheese, cheese.

Conclusion

All representatives of the second group of the main subgroup of the periodic table are necessary for the life and activities of modern man. For example, magnesium is a stimulator of metabolic processes in the body. It should be present in the nervous tissue, blood, bones, liver. Magnesium is an active participant and photosynthesis in plants, since it is an integral part of chlorophyll. Human bones are about a fifth of the total weight. They contain calcium and magnesium. Oxides, alkaline earth metal salts have found a variety of applications in the construction industry, pharmaceuticals and medicine.