Beryllium oxides, magnesium and calcium are. Alkaline earth metals, beryllium, magnesium

Distribution in nature and obtaining. Magnesium and calcium are common elements on Earth (magnesium is the eighth, calcium is the sixth), and the rest of the elements are rarer. Strontium and radium are radioactive elements.

In the earth's crust beryllium is in the form of minerals: beryl Be 3 Al 2 (Si0 3) 6, phenakite Be 2 Si0 4 . Impurity-colored transparent varieties of beryl (green emeralds, blue aquamarines etc.) - precious stones. 54 actually beryllium minerals are known, the most important of them is beryl (and its varieties - emerald, aquamarine, heliodor, sparrowite, rosterite, bazzite).

Magnesium is a part of silicate (among them predominates olivine Mg 2 Si0 4), carbonate ( dolomite CaMg(C0 3) 2 , magnesite MgC0 3) and chloride minerals ( carnallite KClMgCl 2 -6H 2 0). A large amount of magnesium is found in sea water (up to 0.38% MgCl 2) and in the water of some lakes (up to 30% MgCl 2).

Calcium contained in the form of silicates and aluminosilicates in rocks (granites, gneisses, etc.), carbonate in the form calcite CaCO 3, mixtures of calcite and dolomite (marble), sulfate (anhydrite CaS0 4 and gypsum CaS0 4 -2H 2 0) as well as fluoride (fluorite CaF 2) and phosphate (apatite Ca 5 (P0 4) 3), etc.

Essential Minerals strontium and barium: carbonates (strontianite SrC0 3 , witherite BaCO 3) and sulfates (celestine SrS0 4 , barite BaSO 4). Radium found in uranium ores.

In industry beryllium, magnesium, calcium, strontium and barium receive:

• 1) electrolysis of melts of MeCl 2 chlorides, to which NaCl or other chlorides are added to lower the melting point;
• 2) metal- and coal-thermal methods at temperatures of 1000-1300°C.

Particularly pure beryllium is obtained by zone melting. To obtain pure magnesium (99.999% Mg), technical magnesium is repeatedly sublimated in a vacuum. Barium of high purity is obtained by the aluminothermic method from BaO.

Physical and chemical properties. In the form of simple substances, these are shiny silver-white metals, beryllium is hard (it can cut glass), but brittle, the rest are soft and ductile. A feature of beryllium is that it is covered in air with a thin oxide film that protects the metal from the action of oxygen even at high temperatures. Above 800°C, beryllium is oxidized, and at a temperature of 1200°C, metallic beryllium burns out, turning into a white BeO powder.

With an increase in the ordinal number of an element, the density, melting and boiling points increase. The electronegativity of the elements of this group is different. For Be, it is quite high (ze = 1.57), which determines the amphoteric character of its compounds.

All metals in free form are less reactive than alkali metals, but are quite active (they are also stored under kerosene in sealed vessels, and calcium is usually in tightly closed metal cans).

Interaction with simple substances. The chemical activity of metals increases in a subgroup from top to bottom with an increase in the serial number.

In air, they are oxidized to form oxides of MeO, while strontium and barium, when heated in air to ~500°C, form peroxides of Me0 2 , which at higher temperatures decompose into oxide and oxygen. Interaction with simple substances is presented in the diagram:

All metals actively interact with non-metals: with oxygen they form MeO oxides (Me \u003d Be - Ra), with halogens - halides, for example MeCl 2 chlorides, with hydrogen - MeU 2 hydrides, with sulfur - MeS sulfides, with nitrogen - Me 3 nitrides N 2, with carbon - carbides (acetylenides) MeS 2, etc.

With metals, they form eutectic mixtures, solid solutions, and intermetallic compounds. Beryllium with some d-elements forms beryllides - compounds of variable composition MeBe 12 (Me = Ti, Nb, Ta, Mo), MeBe tl (Me = Nb, Ta), characterized by high melting points and resistance to oxidation when heated to 1200-1600°C.

Attitude towards water, acids and alkalis. Beryllium in air is covered with an oxide film, which causes its reduced chemical activity and prevents its interaction with water. It exhibits amphoteric properties, reacts with acids and alkalis with the release of hydrogen. In this case, salts of cationic and anionic types are formed:

Concentrated cold HN0 3 and H 2 S0 4 passivate beryllium.

Magnesium, like beryllium, is resistant to water. It interacts with cold water very slowly, since the resulting Mg (OH) 2 is poorly soluble; when heated, the reaction is accelerated by the dissolution of Mg(OII) 2 . It dissolves very vigorously in acids. The exceptions are HF and H 3 P0 4 , which form sparingly soluble compounds with it. Magnesium, unlike beryllium, does not interact with alkalis.

Calcium subgroup metals (alkaline earth) react with water and dilute hydrochloric and sulfuric acids to release hydrogen and form the corresponding hydroxides and salts:

With alkalis, similarly to magnesium, they do not interact. Properties of compounds of elements of the subgroup HA. Compounds with oxygen. Beryllium oxide and hydroxide are amphoteric in nature, the rest are basic. The bases that are readily soluble in water are Sr (OH) 2 and Ba (OH) 2, they are classified as alkalis.

BeO oxide is refractory (δmelt = 2530°C), has an increased thermal conductivity and, after preliminary calcination at 400°C, chemical inertness. It has an amphoteric character, interacts during fusion with both acidic and basic oxides, as well as with acids and alkalis when heated, forming, respectively, beryllium salts and beryllates:

The corresponding beryllium hydroxide Be (OH) 2 behaves in a similar way - not dissolving in water, it is soluble in both acids and alkalis:

For its precipitation, not alkali is used, but a weak base - ammonium hydroxide:

The hydrolysis of beryllium salts proceeds with the formation of precipitates of poorly soluble basic salts, for example:

Only alkali metal beryllates are soluble.

MgO oxide (burnt magnesia) - refractory (? pl = 2800°C) inert substance. In technology, it is obtained by thermal decomposition of carbonate:

Fine-crystalline MgO, on the contrary, is chemically active and is the main oxide. It interacts with water, absorbs CO 2 , easily dissolves in acids.

oxides alkaline earth metals receive in the laboratory thermal decomposition of the corresponding carbonates or nitrates:

in industry - thermal decomposition of natural carbonates. Oxides vigorously interact with water, forming strong bases, which are second only to alkalis in strength. In the series Be (OH) 2 -> Ca (OH) 2 -> Sr (OH) 2 -> Ba (OH) 2, the basic nature of hydroxides, their solubility and thermal stability are enhanced. All of them vigorously interact with acids to form the corresponding salts:

Unlike beryllium salts, water-soluble salts of alkaline earth metals and magnesium do not undergo cation hydrolysis.

Solubility in water of salts of elements of the PA-subgroup is different. Well soluble are chlorides, bromides, iodides, sulfides (Ca - Ba), nitrates, nitrites (Mg - Ba). Slightly soluble and practically insoluble - fluorides (Mg - Ba), sulfates (Ca - Ba), orthophosphates, carbonates, silicates.

Compounds with hydrogen and non-metals. MeH 2 hydrides, Me 3 N 2 nitrides, MeS 2 carbides (acetylides) are unstable, decompose with water to form the corresponding hydroxides and hydrogen or hydrogen compounds of non-metals:

Application. Beryllium easily forms alloys with many metals, giving them greater hardness, strength, heat resistance and corrosion resistance. Beryllium bronzes (copper alloys with 1-3% beryllium) have unique properties. Unlike pure beryllium, they lend themselves well to machining, for example, they can be used to make strips as thin as 0.1 mm. The tensile strength of these bronzes is greater than that of many alloy steels. As they age, their strength increases. They are non-magnetic, have high electrical and thermal conductivity. Due to this complex of properties, they are widely used in aviation and space technology. In nuclear reactors, beryllium is used as a neutron moderator and reflector. In a mixture with radium preparations, it serves as a source of neutrons produced by the action of alpha particles on Be:

BeO is used as a chemically resistant and refractory material for the manufacture of crucibles and special ceramics.

Magnesium is mainly used for the production of "ultralight" alloys, in metallothermy - for the production of Ti, Zr, V, U, etc. The most important magnesium alloy is electron(3-10% A1 2 0 3, 2-3% Zn, the rest Mg), which, due to its strength and low density (1.8 g / cm 3), is used in rocketry and aircraft engineering. Mixtures of magnesium powder with oxidizing agents are used for lighting and incendiary rockets, projectiles, in photographic and lighting technology. Burnt magnesia MgO is used in the production of magnesium, as a filler in the production of rubber, for the purification of petroleum products, in the production of refractories, building materials, etc.

MgCl 2 chloride is used to obtain magnesium, in the production of magnesia cement, which is obtained by mixing pre-calcined MgO with a 30% aqueous solution of MgCl 2 . This mixture gradually turns into a white solid mass, resistant to acids and alkalis.

The main application of metal calcium - reducing agent in the production of many transition metals, uranium, rare earth elements (REE).

Calcium carbide CaC 2 - for the production of acetylene, CaO - in the production of bleach, Ca (OH) 2, CaC0 3, CaS0 4 H 2 0 - in construction. Ca(OH) 2 ( milk of lime, slaked lime) used as a cheap soluble base. Natural calcium compounds are widely used in the production of binders for mortars, for the manufacture of concrete, building parts and structures. The binders are cements, gypsum materials, lime and others. Gypsum materials are, first of all, burnt gypsum, or alabaster, - hydrate of composition 2CaS0 4 H 2 0. Main application strontium and barium - getters in electrovacuum devices. Solution Ba(OH) 2 ( barite water, caustic barite) - laboratory reagent for a qualitative reaction to CO 2 . Barium titanate (BaTi0 3) is the main component of dielectrics, piezo- and ferroelectrics.

element toxicity. All beryllium compounds are toxic! The dust of beryllium and its compounds is especially dangerous. Strontium and barium, being nerve and muscle poisons, also have general toxicity. Barium compounds cause inflammatory diseases of the brain. The toxicity of barium salts is highly dependent on their solubility. Practically insoluble barium sulfate (pure) is not poisonous, but soluble salts: chloride, nitrate, barium acetate, etc. are highly toxic (0.2-0.5 g of barium chloride cause poisoning, lethal dose - 0.8-0.9 G). The toxic effect of strontium salts is similar to that of barium salts. Oxides of calcium and other alkaline earth metals in the form of dust irritate the mucous membranes, and in contact with the skin causes severe burns. Strontium oxide acts similarly to calcium oxide, but much stronger. Alkaline earth metal salts cause skin diseases.

The structure and properties of atoms. Beryllium Be, magnesium Mg and alkaline earth metals: calcium Ca, strontium Sr, barium Ba and radium Ra are elements of the main subgroup of group II (group IIA) of the Periodic Table of D. I. Mendeleev. The atoms of these elements contain two electrons at the external energy level, which they donate during chemical interactions, and therefore are the strongest reducing agents. In all compounds, they have an oxidation state of +2.

With an increase in the serial number from top to bottom in the subgroup, the reducing properties of the elements are enhanced, which is associated with an increase in the radii of their atoms.

Radium is a radioactive element, its content in nature is small.

Beryllium, magnesium and alkaline earth metals are simple substances. Light silvery-white metals, strontium has a golden hue. It is much harder than barium, while barium is softer than lead.

In air at normal temperature, the surface of beryllium and magnesium is covered with a protective oxide film. Alkaline earth metals interact with atmospheric oxygen more actively, so they are stored under a layer of kerosene or in sealed vessels, like alkali metals.

When heated in air, all the metals under consideration (we denote them by M) burn vigorously with the formation of oxides:

The combustion reaction of magnesium is accompanied by a blinding flash, it was previously used when photographing objects in dark rooms. Currently using an electric flash.

Beryllium, magnesium and all alkaline earth metals interact when heated with non-metals - chlorine, sulfur, nitrogen, etc., forming chlorides, sulfides and nitrides, respectively:

At high temperatures, metals of the main subgroup of group II (group IIA) of the Periodic Table of D. I. Mendeleev are oxidized by hydrogen to hydrides:

Hydrides are solid salt-like compounds of metals with hydrogen, similar to halides - compounds of metals with halogens. Now, obviously, it has become clear to you why hydrogen is also in the main subgroup of group VII (group VIIA).

Of all the metals of the main subgroup of group II (group IIA) of the Periodic Table of D. I. Mendeleev, only beryllium practically does not interact with water (a protective film on its surface prevents it), magnesium reacts with it slowly, the rest of the metals interact violently with water under normal conditions ( Fig. 54):

Rice. 54.
Interaction with water of metals of the main subgroup of group II (group IIA) of the Periodic system of D. I. Mendeleev

Like aluminum, magnesium and calcium are able to restore rare metals - niobium, tantalum, molybdenum, tungsten, titanium, etc. - from their oxides, for example:

Such methods of obtaining metals, by analogy with aluminothermy, are called magnesiumthermy and calciumthermy.

Magnesium and calcium are used to produce rare metals and light alloys. For example, magnesium is part of duralumin, and calcium is one of the components of lead alloys required for the manufacture of bearings and cable sheaths.

Compounds of beryllium, magnesium and alkaline earth metals. In nature, alkaline earth metals, like alkali metals, are found only in the form of compounds due to their high chemical activity.

MO oxides are solid white refractory substances resistant to high temperatures. They exhibit basic properties, except for beryllium oxide, which has an amphoteric character.

Magnesium oxide is inactive in the reaction with water, all other oxides interact very violently with it:

MO + H 2 O \u003d M (OH) 2.

Oxides are obtained by roasting carbonates:

MSO 3 \u003d MO + CO 2.

In engineering, calcium oxide CaO is called quicklime, and MgO is called burnt magnesia. Both of these oxides are used in the production of building materials.

Laboratory experiment No. 15
Preparation of calcium hydroxide and study of its properties

Hydroxides of alkaline earth metals are alkalis. Their solubility in water increases in the series

Ca (OH) 2 → Sr (OH) 2 → Ba (OH) 2.

These hydroxides are obtained by reacting the corresponding oxide with water.

The reaction of calcium oxide with water is accompanied by the release of a large amount of heat and is called lime slaking (Fig. 55), and the resulting Ca (OH) 2 is called slaked lime:

CaO + H 2 O \u003d Ca (OH) 2.

Rice. 55.
lime slaking

A transparent solution of calcium hydroxide is called lime water, and a white suspension of Ca (OH) 2 in water is called lime milk. Slaked lime is widely used in construction. Milk of lime is used in the sugar industry to purify sugar beet juice.

Salts of beryllium, magnesium and alkaline earth metals are obtained by reacting them with acids. The halides (fluorides, chlorides, bromides and iodides) of these metals are white crystalline substances, most of them soluble in water. Of the sulfates, only beryllium and magnesium sulfates are readily soluble in water. The solubility of sulfates of the elements of the main subgroup of group II of the Periodic Table of D. I. Mendeleev decreases from BeSO 4 to BaSO 4. The carbonates of these metals are sparingly soluble or insoluble in water.

Alkaline earth metal sulfides, containing small amounts of heavy metal impurities, after preliminary illumination, begin to glow in various colors - red, orange, blue, green. They are part of special luminous paints, which are called phosphors. They are used for the manufacture of luminous road signs, watch dials and other products.

Consider the most important compounds of the elements of the main subgroup of group II (group IIA) of the Periodic system of D. I. Mendeleev.

CaCO 3 - calcium carbonate - one of the most common compounds on Earth. You are well aware of such minerals containing it as chalk, marble, limestone (Fig. 56).

Rice. 56.
Natural calcium compounds: a - chalk; b - marble; c - limestone; g - calcite

Marble is the mineral of sculptors, architects and tilers. Many sculptors created their beautiful creations from it (Fig. 57).

Rice. 57.
The sculpture of M. M. Antokolsky "Tsar Ivan Vasilyevich the Terrible" is made of marble

The walls of the world-famous Indian mausoleum Taj Mahal are made of marble (Fig. 58), many stations of the Moscow metro are lined with it (Fig. 59).

Rice. 58.
Taj Mahal - a mausoleum-mosque located in Agra (India), made of marble

Rice. 59.
Moscow metro station "Trubnaya" is finished with marble

However, the most important of these minerals is limestone, without which no building can do. Firstly, he himself is an excellent building stone (remember the famous Odessa catacombs - former quarries in which stone was mined for the construction of the city), and secondly, it is a raw material for obtaining other materials: cement, slaked and quicklime, glass, etc.

Roads are strengthened with lime gravel, and soil acidity is reduced with powder.

Natural chalk is the remains of shells of ancient animals. One example of its use is school crayons, toothpastes. Chalk is used in the production of paper, rubber, whitewash.

MgCO 2 - magnesium carbonate, is necessary in the production of glass, cement, bricks, as well as in metallurgy to transfer waste rock, that is, not containing a metal compound, into slag.

CaSO 4 - calcium sulfate, occurs in nature in the form of the mineral gypsum CaSO 4 2H 2 O, which is a crystalline hydrate. They are used in construction, in medicine for applying fixing plaster bandages, making casts (Fig. 60). For this, hemihydrate gypsum 2CaSO 4 H 2 O is used - alabaster, which, when interacting with water, forms dihydrate gypsum:

2CaSO 4 H 2 O + ZH 2 O \u003d 2 (CaSO 4 2H 2 O).

This reaction proceeds with the release of heat.

Rice. 60.
Gypsum is used:
in medicine for the manufacture of plaster casts (1), artificial facing and finishing stones (2), in construction for the manufacture of sculptures and sculptural elements (3), drywall (4)

MgSO 4 - magnesium sulfate, known as bitter, or Epsom salt, is used in medicine as a laxative. Contained in sea water and gives it a bitter taste.

BaSO 4 - barium sulfate, due to its insolubility and ability to delay x-rays, it is used in x-ray diagnostics ("barite porridge") for the diagnosis of diseases of the gastrointestinal tract (Fig. 61).

Rice. 61. "Barite porridge" is used in medicine for X-ray diagnostics

Ca 3 (PO 4) 2 - calcium phosphate, is part of phosphorites (rock) and apatites (mineral), as well as in the composition of bones and teeth. The body of an adult contains more than 1 kg of calcium in the form of Ca 3 (PO 4) 2.

Calcium is essential for living organisms, it is a material for the construction of the bone skeleton. It plays an essential role in life processes: calcium ions are necessary for the work of the heart, participate in the processes of blood coagulation.

Calcium accounts for more than 1.5% of human body weight, 98% of calcium is found in the bones. However, calcium is necessary not only for the formation of the skeleton, but also for the functioning of the nervous system.

A person should receive 1.5 g of calcium per day. The largest amounts of calcium are found in cheese, cottage cheese, parsley, and lettuce.

Magnesium is also an essential bioelement, playing the role of a metabolic stimulant, found in the liver, bones, blood, nervous tissue and brain. Magnesium in the human body is much less than calcium - only about 40 g. Magnesium is part of chlorophyll, and therefore participates in the processes of photosynthesis. Without chlorophyll, there would be no life, and without magnesium, there would be no chlorophyll, because it contains 2% of this element.

Alkaline earth metal salts color flames bright colors, so these compounds are added to fireworks compositions (Fig. 62).

Rice. 62.
Alkaline earth metal salts are added to fireworks compositions

Discovery of magnesium and calcium. Magnesium was first obtained by G. Davy in 1808 from white magnesia, a mineral found near the Greek city of Magnesia. By the name of the mineral, they gave the name to a simple substance and a chemical element.

The metal obtained by G. Davy was contaminated with impurities, and pure magnesium was received by the Frenchman A. Bussy in 1829.

Calcium was also first obtained by G. Davy in 1808. The name of the element comes from the Latin word cals, which means "lime, soft stone."

New words and concepts

1. The structure of the atoms of beryllium and magnesium, alkaline earth metals.
2. Chemical properties of beryllium, magnesium and alkaline earth metals: formation of oxides, chlorides, sulfides, nitrides, hydrides and hydroxides.
3. Magnesium and calcium.
4. Oxides of calcium (quicklime) and magnesium (burnt magnesia). 5. Calcium hydroxides (slaked lime, lime water, milk of lime) and other alkaline earth metals.
5. Salts: calcium carbonates (chalk, marble, limestone) and magnesium; sulfates (gypsum, bitter salt, "barite porridge"); phosphates.

Alkaline earth metals include metals of group IIA of the Periodic Table of D.I. Mendeleev - calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). In addition to them, the main subgroup of group II includes beryllium (Be) and magnesium (Mg). The outer energy level of alkaline earth metals has two valence electrons. The electronic configuration of the external energy level of alkaline earth metals is ns 2 . In their compounds, they exhibit a single oxidation state equal to +2. In OVR, they are reducing agents, i.e. donate an electron.

With an increase in the charge of the nucleus of atoms of elements that are part of the group of alkaline earth metals, the ionization energy of atoms decreases, and the radii of atoms and ions increase, the metallic signs of chemical elements increase.

Physical properties of alkaline earth metals

In the free state, Be is a steel-gray metal with a dense hexagonal crystal lattice, rather hard and brittle. In air, Be is covered with an oxide film, which gives it a matte tint and reduces its chemical activity.

Magnesium in the form of a simple substance is a white metal, which, like Be, acquires a matte hue when exposed to air due to the formation of an oxide film. Mg is softer and more ductile than beryllium. The crystal lattice of Mg is hexagonal.

Free Ca, Ba and Sr are silver-white metals. When exposed to air, they are instantly covered with a yellowish film, which is the products of their interaction with the constituent parts of the air. Calcium is a rather hard metal, Ba and Sr are softer.

Ca and Sr have a cubic face-centered crystal lattice, barium has a cubic body-centered crystal lattice.

All alkaline earth metals are characterized by the presence of a metallic type of chemical bond, which causes their high thermal and electrical conductivity. The boiling and melting points of alkaline earth metals are higher than those of alkali metals.

Obtaining alkaline earth metals

Getting Be is carried out by the reduction reaction of its fluoride. The reaction proceeds when heated:

BeF 2 + Mg = Be + MgF 2

Magnesium, calcium and strontium are obtained by electrolysis of molten salts, most often chlorides:

CaCl 2 \u003d Ca + Cl 2

Moreover, when Mg is obtained by electrolysis of a dichloride melt, NaCl is added to the reaction mixture to lower the melting temperature.

To obtain Mg in industry, metal- and carbon-thermal methods are used:

2(CaO×MgO) (dolomite) + Si = Ca 2 SiO 4 + Mg

The main way to obtain Ba is oxide reduction:

3BaO + 2Al = 3Ba + Al 2 O 3

Chemical properties of alkaline earth metals

Since in n.a. the surface of Be and Mg is covered with an oxide film - these metals are inert with respect to water. Ca, Sr and Ba dissolve in water to form hydroxides exhibiting strong basic properties:

Ba + H 2 O \u003d Ba (OH) 2 + H 2

Alkaline earth metals are able to react with oxygen, and all of them, with the exception of barium, form oxides as a result of this interaction, barium - peroxide:

2Ca + O 2 \u003d 2CaO

Ba + O 2 \u003d BaO 2

Oxides of alkaline earth metals, with the exception of beryllium, exhibit basic properties, Be - amphoteric properties.

When heated, alkaline earth metals are capable of interacting with non-metals (halogens, sulfur, nitrogen, etc.):

Mg + Br 2 \u003d 2MgBr

3Sr + N 2 \u003d Sr 3 N 2

2Mg + 2C \u003d Mg 2 C 2

2Ba + 2P = Ba 3 P 2

Ba + H 2 = BaH 2

Alkaline earth metals react with acids - dissolve in them:

Ca + 2HCl \u003d CaCl 2 + H 2

Mg + H 2 SO 4 \u003d MgSO 4 + H 2

Beryllium reacts with aqueous solutions of alkalis - it dissolves in them:

Be + 2NaOH + 2H 2 O \u003d Na 2 + H 2

Qualitative reactions

A qualitative reaction to alkaline earth metals is the coloring of the flame with their cations: Ca 2+ colors the flame dark orange, Sr 2+ dark red, Ba 2+ light green.

A qualitative reaction to the barium cation Ba 2+ are SO 4 2- anions, resulting in the formation of a white precipitate of barium sulfate (BaSO 4), insoluble in inorganic acids.

Ba 2+ + SO 4 2- \u003d BaSO 4 ↓

Examples of problem solving

EXAMPLE 1

Alkaline earth metals are elements that belong to the second group of the periodic table. These include substances such as calcium, magnesium, barium, beryllium, strontium and radium. The name of this group indicates that in water they give an alkaline reaction.

Alkali and alkaline earth metals, or rather their salts, are widely distributed in nature. They are represented by minerals. The exception is radium, which is considered a fairly rare element.

All of the above metals have some common qualities, which made it possible to combine them into one group.

Alkaline earth metals and their physical properties

Almost all of these elements are grayish solids (at least under normal conditions and by the way, the physical properties are slightly different - these substances, although quite persistent, are easily affected.

Interestingly, with the serial number in the table, such an indicator of the metal as density also grows. For example, in this group, calcium has the lowest index, while radium is similar in density to iron.

Alkaline earth metals: chemical properties

To begin with, it is worth noting that the chemical activity increases according to the serial number of the periodic table. For example, beryllium is a fairly stable element. It reacts with oxygen and halogens only when heated strongly. The same goes for magnesium. But calcium is able to slowly oxidize already at room temperature. The remaining three representatives of the group (radium, barium and strontium) quickly react with atmospheric oxygen already at room temperature. That is why these elements are stored, covering with a layer of kerosene.

The activity of oxides and hydroxides of these metals increases in the same way. For example, beryllium hydroxide does not dissolve in water and is considered an amphoteric substance, but is considered a fairly strong alkali.

Alkaline earth metals and their brief characteristics

Beryllium is a light gray hard metal with high toxicity. The element was first discovered in 1798 by the chemist Vauquelin. There are several minerals of beryllium in nature, of which the following are considered the most famous: beryl, phenakite, danalite and chrysoberyl. By the way, some beryllium isotopes are highly radioactive.

Interestingly, some forms of beryl are valuable gemstones. These include emerald, aquamarine and heliodor.

Beryllium is used to make some alloys. This element is used to slow down neutrons.

Calcium is one of the best known alkaline earth metals. In its pure form, it is a soft white substance with a silvery tint. Pure calcium was first isolated in 1808. In nature, this element is present in the form of minerals such as marble, limestone and gypsum. Calcium is widely used in modern technologies. It is used as a chemical fuel source and also as a fire retardant material. It's no secret that calcium compounds are used in the production of building materials and medicines.

This element is also found in every living organism. Basically, he is responsible for the operation of the motor apparatus.

Magnesium is a light and quite malleable metal with a characteristic grayish color. It was isolated in its pure form in 1808, but its salts became known much earlier. Magnesium is found in minerals such as magnesite, dolomite, carnallite, kieserite. By the way, magnesium salt provides a huge number of compounds of this substance can be found in sea water.