Group II metals are alkaline earth metals magnesium and beryllium. Beryllium, magnesium and alkaline earth metals Chemical elements magnesium calcium and beryllium

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 by 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 ↓

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Group IIA contains only metals - Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium) and Ra (radium). The chemical properties of the first representative of this group, beryllium, differ most strongly from the chemical properties of the other elements of this group. Its chemical properties are in many ways even more similar to aluminum than to other group IIA metals (the so-called "diagonal similarity"). Magnesium, in terms of chemical properties, also differs markedly from Ca, Sr, Ba, and Ra, but still has much more similar chemical properties with them than with beryllium. Due to the significant similarity of the chemical properties of calcium, strontium, barium and radium, they are combined into one family, called alkaline earth metals.

All elements of group IIA belong to s-elements, i.e. contain all of their valence electrons s-sublevel. Thus, the electronic configuration of the outer electron layer of all chemical elements of this group has the form ns 2 , where n– number of the period in which the element is located.

Due to the peculiarities of the electronic structure of group IIA metals, these elements, in addition to zero, are capable of having only one single oxidation state, equal to +2. Simple substances formed by elements of group IIA, when participating in any chemical reactions, can only be oxidized, i.e. donate electrons:

Me 0 - 2e - → Me +2

Calcium, strontium, barium and radium are extremely reactive. The simple substances formed by them are very strong reducing agents. Magnesium is also a strong reducing agent. The reducing activity of metals obeys the general laws of the periodic law of D.I. Mendeleev and increases down the subgroup.

Interaction with simple substances

with oxygen

Without heating, beryllium and magnesium do not react with either atmospheric oxygen or pure oxygen due to the fact that they are covered with thin protective films consisting of BeO and MgO oxides, respectively. Their storage does not require any special methods of protection from air and moisture, unlike alkaline earth metals, which are stored under a layer of a liquid inert to them, most often kerosene.

Be, Mg, Ca, Sr, when burned in oxygen, form oxides of the composition MeO, and Ba - a mixture of barium oxide (BaO) and barium peroxide (BaO 2):

2Mg + O 2 \u003d 2MgO

2Ca + O 2 \u003d 2CaO

2Ba + O 2 \u003d 2BaO

Ba + O 2 \u003d BaO 2

It should be noted that during the combustion of alkaline earth metals and magnesium in air, the reaction of these metals with atmospheric nitrogen also proceeds side by side, as a result of which, in addition to compounds of metals with oxygen, nitrides with the general formula Me 3 N 2 are also formed.

with halogens

Beryllium reacts with halogens only at high temperatures, while the rest of the Group IIA metals already at room temperature:

Mg + I 2 \u003d MgI 2 - magnesium iodide

Ca + Br 2 \u003d CaBr 2 - calcium bromide

Ba + Cl 2 \u003d BaCl 2 - barium chloride

with non-metals of IV–VI groups

All metals of group IIA react when heated with all non-metals of groups IV-VI, but depending on the position of the metal in the group, as well as the activity of non-metals, a different degree of heating is required. Since beryllium is the most chemically inert among all metals of group IIA, its reactions with nonmetals require significantly more about high temperature.

It should be noted that the reaction of metals with carbon can form carbides of various nature. There are carbides related to methanides and conventionally considered derivatives of methane, in which all hydrogen atoms are replaced by a metal. They, like methane, contain carbon in the -4 oxidation state, and during their hydrolysis or interaction with non-oxidizing acids, methane is one of the products. There is also another type of carbides - acetylenides, which contain the C 2 2- ion, which is actually a fragment of the acetylene molecule. Carbides of the acetylenide type upon hydrolysis or interaction with non-oxidizing acids form acetylene as one of the reaction products. What type of carbide - methanide or acetylenide - will be obtained by the interaction of one or another metal with carbon depends on the size of the metal cation. As a rule, methanides are formed with metal ions having a small radius, and acetylides with larger ions. In the case of metals of the second group, methanide is obtained by the interaction of beryllium with carbon:

The remaining metals of group II A form acetylenides with carbon:

With silicon, group IIA metals form silicides - compounds of the Me 2 Si type, with nitrogen - nitrides (Me 3 N 2), phosphorus - phosphides (Me 3 P 2):

with hydrogen

All alkaline earth metals react when heated with hydrogen. In order for magnesium to react with hydrogen, heating alone, as in the case of alkaline earth metals, is not enough; in addition to high temperature, an increased pressure of hydrogen is also required. Beryllium does not react with hydrogen under any conditions.

Interaction with complex substances

with water

All alkaline earth metals actively react with water to form alkalis (soluble metal hydroxides) and hydrogen. Magnesium reacts with water only during boiling, due to the fact that when heated, the protective oxide film of MgO dissolves in water. In the case of beryllium, the protective oxide film is very resistant: water does not react with it either when boiling or even at a red heat temperature:

with non-oxidizing acids

All metals of the main subgroup of group II react with non-oxidizing acids, since they are in the activity series to the left of hydrogen. In this case, a salt of the corresponding acid and hydrogen are formed. Reaction examples:

Be + H 2 SO 4 (razb.) \u003d BeSO 4 + H 2

Mg + 2HBr \u003d MgBr 2 + H 2

Ca + 2CH 3 COOH = (CH 3 COO) 2 Ca + H 2

with oxidizing acids

− dilute nitric acid

All Group IIA metals react with dilute nitric acid. In this case, the reduction products instead of hydrogen (as in the case of non-oxidizing acids) are nitrogen oxides, mainly nitrogen oxide (I) (N 2 O), and in the case of highly dilute nitric acid, ammonium nitrate (NH 4 NO 3):

4Ca + 10HNO 3 ( razb .) \u003d 4Ca (NO 3) 2 + N 2 O + 5H 2 O

4Mg + 10HNO3 (very disaggregated)\u003d 4Mg (NO 3) 2 + NH 4 NO 3 + 3H 2 O

− concentrated nitric acid

Concentrated nitric acid at ordinary (or low) temperature passivates beryllium, i.e. does not react with it. When boiling, the reaction is possible and proceeds mainly in accordance with the equation:

Magnesium and alkaline earth metals react with concentrated nitric acid to form a wide range of different nitrogen reduction products.

− concentrated sulfuric acid

Beryllium is passivated with concentrated sulfuric acid, i.e. does not react with it under normal conditions, however, the reaction proceeds during boiling and leads to the formation of beryllium sulfate, sulfur dioxide and water:

Be + 2H 2 SO 4 → BeSO 4 + SO 2 + 2H 2 O

Barium is also passivated by concentrated sulfuric acid due to the formation of insoluble barium sulfate, but reacts with it when heated, barium sulfate dissolves when heated in concentrated sulfuric acid due to its conversion to barium hydrogen sulfate.

The remaining metals of the main group IIA react with concentrated sulfuric acid under any conditions, including in the cold. Sulfur reduction can occur to SO 2, H 2 S and S, depending on the activity of the metal, the reaction temperature and the concentration of the acid:

Mg + H 2 SO 4 ( conc .) \u003d MgSO 4 + SO 2 + H 2 O

3Mg + 4H2SO4 ( conc .) \u003d 3MgSO 4 + S↓ + 4H 2 O

4Ca + 5H2SO4 ( conc .) \u003d 4CaSO 4 + H 2 S + 4H 2 O

with alkalis

Magnesium and alkaline earth metals do not interact with alkalis, and beryllium easily reacts both with alkali solutions and with anhydrous alkalis during fusion. Moreover, when the reaction is carried out in an aqueous solution, water also participates in the reaction, and the products are tetrahydroxoberyllates of alkali or alkaline earth metals and gaseous hydrogen:

Be + 2KOH + 2H 2 O \u003d H 2 + K 2 - potassium tetrahydroxoberyllate

When carrying out the reaction with solid alkali during fusion, beryllates of alkali or alkaline earth metals and hydrogen are formed.

Be + 2KOH \u003d H 2 + K 2 BeO 2 - potassium beryllate

with oxides

Alkaline earth metals, as well as magnesium, can reduce less active metals and some non-metals from their oxides when heated, for example:

The method of restoring metals from their oxides with magnesium is called magnesiumthermy.

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 even at room temperature. The remaining three representatives of the group (radium, barium and strontium) quickly react with atmospheric oxygen even 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 fairly 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.