Beryllium is an alkali metal. Beryllium, magnesium and alkaline earth metals - Knowledge Hypermarket
The concept of alkaline earth metals includes a part of the elements of group II of the Mendeleev system: beryllium, magnesium, calcium, strontium, barium, radium. The last four metals have the most pronounced signs of the alkaline earth classification, therefore, in some sources, beryllium and magnesium are not included in the list, limited to four elements.
The metal got its name due to the fact that when their oxides interact with water, an alkaline environment is formed. Physical properties of alkaline earth metals: all elements have a gray metallic color, under normal conditions they have a solid structure, their density increases with increasing serial number, and they have a very high melting point. Unlike alkali metals, the elements of this group are not cut with a knife (with the exception of strontium). Chemical properties of alkaline earth metals: they have two valence electrons, activity increases with increasing atomic number, act as a reducing agent in reactions.
The characteristic of alkaline earth metals indicates their high activity. In particular, this applies to elements with a large serial number. For example, under normal conditions, beryllium does not interact with oxygen and halogens. To start the response mechanism, it must be heated to a temperature of over 600 degrees Celsius. Magnesium under normal conditions has an oxide film on the surface and also does not react with oxygen. Calcium is oxidized, but rather slowly. But strontium, barium and radium oxidize almost instantly, so they are stored in an oxygen-free environment under a kerosene layer.
All oxides enhance the basic properties with an increase in the ordinal number of the metal. Beryllium hydroxide is an amphoteric compound that does not react with water, but is highly soluble in acids. Magnesium hydroxide is a weak alkali, insoluble in water but reactive with strong acids. Calcium hydroxide is a strong, water-soluble base that reacts with acids. Barium and strontium hydroxides are strong bases that are readily soluble in water. And radium hydroxide is one of the strongest alkalis, which reacts well with water and almost all types of acids.
How to get
Alkaline earth metal hydroxides are obtained by exposing a pure element to water. The reaction proceeds at room conditions (except for beryllium, which requires an increase in temperature) with the release of hydrogen. When heated, all alkaline earth metals react with halogens. The resulting compounds are used in the production of a wide range of products from chemical fertilizers to ultra-precise microprocessor parts. Alkaline earth metal compounds exhibit the same high activity as pure elements, so they are used in many chemical reactions.
Most often this occurs during exchange reactions, when it is necessary to displace a less active metal from a substance. They take part in redox reactions as a strong reducing agent. Divalent calcium and magnesium cations give water the so-called hardness. This phenomenon is overcome by precipitation of ions with the help of physical impact or by adding special emollients to the water. Alkaline earth metal salts are formed by dissolving elements in acid or as a result of exchange reactions. The resulting compounds have a strong covalent bond, and therefore have a low electrical conductivity.
In nature, alkaline earth metals cannot be found in their pure form, as they quickly interact with the environment, forming chemical compounds. They are part of the minerals and rocks contained in the thickness of the earth's crust. Calcium is the most common, magnesium is slightly inferior to it, barium and strontium are quite common. Beryllium is a rare metal, while radium is a very rare one. For all the time that has passed since the discovery of radium, only one and a half kilograms of pure metal has been mined all over the world. Like most radioactive elements, radium has four isotopes.
Alkaline earth metals are obtained by decomposing complex substances and isolating a pure substance from them. Beryllium is mined by reducing it from fluoride at high temperatures. Barium recovers from its oxide. Calcium, magnesium and strontium are obtained by electrolysis of their chloride melt. The most difficult thing is to synthesize pure radium. It is mined by impact on uranium ore. According to scientists, on average, one ton of ore accounts for 3 grams of pure radium, although there are also rich deposits that contain as much as 25 grams per ton. The methods of precipitation, fractional crystallization and ion exchange are used to isolate the metal.
Application of alkaline earth metals
The range of application of alkaline earth metals is very extensive and covers many industries. Beryllium is in most cases used as an alloying additive in various alloys. It increases the hardness and strength of materials, well protects the surface from corrosion. Also, due to the weak absorption of radioactive radiation, beryllium is used in the manufacture of X-ray machines and in nuclear energy.
Magnesium is used as one of the reducing agents in the production of titanium. Its alloys are distinguished by high strength and lightness, therefore they are used in the manufacture of aircraft, cars, rockets. Magnesium oxide burns with a bright, blinding flame, which is reflected in the military, where it is used to make incendiary and tracer shells, flares, and flashbang grenades. It is one of the most important elements for the regulation of the normal process of vital activity of the body, therefore it is part of some drugs.
Calcium in its pure form is practically not used. It is needed to restore other metals from their compounds, as well as in the production of drugs to strengthen bone tissue. Strontium is used to reduce other metals and as the main component for the production of superconducting materials. Barium is added to many alloys that are designed to work in aggressive environments, as it has excellent protective properties. Radium is used in medicine for short-term skin irradiation in the treatment of malignant tumors.
S-elements 2 groups
GENERAL CHARACTERISTICS. To alkaline earth metals usually
include calcium, strontium and barium, since their oxides (earths) at
dissolving in water gives alkali. beryllium and magnesium oxides in water
dissolve. Sometimes all metals from group 2A are called
alkaline earth. At the outer level, atoms have 2 electrons (Be -
2s2, Mg - 3s2, Ca - 4s2, etc.).
When excited, s-electrons go to p-
sublevel and then the formation of two bonds is possible
(valency is two). In metal compounds
exhibit an oxidation state of +2.
1. Alkaline earth metals are strong reducing agents, although
inferior to alkali metals. Restorative properties are growing
from top to bottom, which coincides with an increase in atomic radii (Be - 0.113
nm, Ba - 0.221 nm) and the weakening of the bond between the electrons and the nucleus. So, Be and Mg
decompose water very slowly, while Ca, Sr, Ba rapidly.
2. In air, Be and Mg are covered with a protective film and burn out when
only when ignited, while Ca, Sr, Ba self-ignite when
contact with air.
3. Be and Mg oxides are insoluble in water and Be and Mg hydroxides
are obtained indirectly, while the oxides Ca, Sr, Ba are combined with
water to form hydroxides. Beryllium oxide has amphoteric
properties, the remaining oxides are the main properties.
4. Be (OH) 2 and Mg (OH) 2 are almost insoluble in water (0.02 and 2 mg per 100 g).
The solubility of Ca(OH)2, Sr(OH)2, Ba(OH)2 is 0.1, 0.7 and 3.4 g.
this Be (OH) 2 is an amphoteric hydroxide, Mg (0H) 2, is a weak base,
Ca(OH)2, Sr(OH)2, Ba(0H)2 are strong bases.
5. The halides are highly soluble in water, but the solubility
sulfate falls from top to bottom. So, 35.6 g dissolves in 100 g of water.
MgSO4, but only 0.2 g CaSO4, 0.01 g SrSO4 and 0.0002 g BaSO4.
6. The solubility of carbonates decreases from top to bottom. MgCO3 - 0.06 g per
100 g of water, BaCO3 in total - 0.002 g. Thermal stability of carbonates
grows from top to bottom: If BeCO3 decomposes at 100o, MgCO3 - at 350o, then
CaCO3 - at 900o, SrCO3 - 1290o BaCO3 - at 1350o.
BERYLLIUM - has more pronounced covalent
(non-metallic) properties than other group 2A elements. And myself
beryllium, its oxide and hydroxide have amphoteric properties.
Be + 2HCl = BeCl2 + H2 Be + 2KOH + 2H2O = K2 + H2
BeO + 2HCl = BeCl2 + H2O BeO + 2KOH + H2O = K2
Be(OH)2 + 2HCl = BeCl2 + 2H2O Be(OH)2 + 2KOH = K2
Magnesium and calcium
GENERAL INFORMATION. The content of magnesium and calcium in the earth's crust 2.1
and 3.6%. Minerals magnesium- MgCO3. CaCO3 - dolomite, MgCO3 - magnesite, KCl.
6H2O - carnallite; MgSO4
KCl. 3H2O - kainite. Minerals calcium:
CaCO3 - calcite (limestone, chalk, marble), СaSO4
2H2O - gypsum, Ca3(PO4)2 -
phosphorite, 3Ca3(PO4)2
CaF2 - apatite.
Magnesium and calcium - silver-white metals melt at 651 and
851o C. Calcium and its salts color the flame brick red.
RECEIVING. Calcium and magnesium are obtained by electrolysis of the melt
calcium chloride or magnesium chloride or by the aluminothermic method.
electrolysis to
СaCl2 Ca + Cl2 4CaO + 2Al = 3Ca + CaO . Al2O3
Chemical properties of calcium and magnesium.
In compounds, both metals exhibit an oxidation state of +2. At
In this case, calcium is more active than magnesium, although it is inferior to strontium and
1. Interaction with oxygen comes with ignition and
release of heat and light.
Mg + O2 = 2MgO; 2Ca + O2 = 2CaO
2. Interaction with halogens. Fluorine combines with Ca and Mg
directly, the remaining halogens only when heated.
Mg + Cl2 = MgCl2; Ca + Br2 = CaBr2
3. When heated, Ca and Mg form hydrides with hydrogen, which
easily hydrolyzed and oxidized. to to
Mg + H2 = MgH2; Ca + H2 = CaH2
CaH2 + 2H2O = Ca(OH)2 + 2H2; CaH2 + O2 = CaO + H2O
4. When heated, both metals interact with others
non-metals:
Mg + S = MgS; 3Ca + N2 = Ca3N2; 3Mg + 2P = Mg3P2
3Ca + 2As = Mg3As2; Ca + 2C = CaC2; Mg + 2C = MgC2
Nitrides, sulfides and carbides of calcium and magnesium are susceptible to
hydrolysis:
Ca3N2 + 6H2O = 3Ca(OH)2 + 2NH3; CaC2 + 2H2O = Ca(OH)2 +
5. Beryllium and magnesium interact with water and alcohols only
when heated, while calcium violently displaces from them
Mg + H2O = MgO + H2; Ca + 2H2O = Ca(OH)2 + H2
Ca + 2C2H5OH \u003d Ca (C2H5O) 2 + H2
6. Magnesium and calcium take away oxygen from less active oxides
metals.
CuO + Mg = Cu + MgO; MoO3 + 3Ca = Mo + 3CaO
7. Magnesium and calcium displace hydrogen from non-oxidizing acids,
and oxidizing acids deeply reduce these metals.
Mg + 2HCl = MgCl2 + H2; Ca + 2CH3COOH = Ca(CH3COO)2 + H2
3Mg + 4H2SO4c = 3MgSO4 + S + 4H2O; 4Ca + 10HNO3c = 4Ca(NO3)2 + N2O
4Ca + 10HNO3 = 4Ca(NO3)2 + NH4NO3 + 3H2O
8. Calcium and magnesium are easily oxidized by solutions of oxidizing agents:
5Mg + 2KMnO4 + 8H2SO4 = 5MgSO4 + 2MnSO4 + K2SO4 + 8H2O
Ca + K2Cr2O7 + 7H2SO4 = 3CaSO4 + Cr2(SO4)3 + K2SO4 + 7H2O
Oxides calcium and magnesium hydroxides.
Magnesium oxide - MgO- white powder, refractory (refractory),
insoluble in water and acids and only amorphous oxide form
magnesium reacts slowly with acids. Get magnesium oxide
heating magnesium hydroxide.
MgO (amorphous) + 2HCl = MgCl2 + H2O; Mg(OH)2 = MgO + H2O
Magnesium hydroxide - Mg(OH)2- insoluble and
low dissociating base. Obtained by the action of alkalis on salts
magnesium. When carbon dioxide is passed through its solution,
precipitate of magnesium carbonate, which subsequently dissolves when
excess CO2.
MgCl2 + 2KOH = Mg(OH)2 + 2KCl MgCl2 + 2NH4OH = Mg(OH)2 + 2NH4Cl
Mg(OH)2 + CO2 = MgCO3 + H2O MgCO3 + CO2 + H2O = Mg(HCO3)2
Calcium oxide - CaO- quicklime. White refractory
a substance with pronounced basic properties (forms with water
hydroxide, reacts with acid oxides, acids and amphoteric
oxides).
CaO + H2O = Ca(OH)2 CaO + CO2 = CaCO3 CaO + 2HCl = CaCl2
CaO + Al2O3 = Ca(AlO2)2 CaO + Fe2O3 = Ca(FeO2)2
Obtained by roasting limestone or sulfate reduction
CaCO3 = CaO + CO2; 2СаSO4 + 2C = 2CaO + 2SO2 + CO2
calcium hydroxide Ca(OH)2- slaked lime (fluff), get
when calcium oxide reacts with water. Strong base except
It dissolves some non-metals and amphoteric metals.
Ca(OH)2 + 2HCl = CaCl2 + 2H2O Ca(OH)2 + SO3 = CaSO4 +
3Ca(OH)2 2FeCl3 = 2Fe(OH)3+ 3CaCl2 2NH4Cl + Ca(OH)2 = CaCl2 + NH3
2Ca(OH)2 + Cl2 = CaCl2 + Ca(ClO)2 + 2H2O Ca(OH)2 + 2Al + 2H2O =
Slaked lime is part of the mortar.
Solidification is based on the reactions:
Ca(OH)2 + CO2 = CaCO3 + H2O; Ca(OH)2 + SiO2 = CaSiO3 + H2O
sand from the air
When carbon dioxide is passed through a solution of Ca(OH)2
(lime water), calcium carbonate precipitates, which, when
further transmission of CO2 dissolves due to the formation
soluble calcium bicarbonate.
Ca(OH)2 + CO2 = CaCO3 + H2O; CaCO3 + CO2 + H2O = Ca(HCO3)2
GROUP II METALS ALKALINE EARTH METALS, MAGNESIUM AND BERYLLIUM Not all elements of group IIA are alkaline earth, but only starting from calcium and down the group. The oxides of these elements ("earths" - in the old terminology) interact with
POSITION IN PSCE AND STRUCTURE OF ATOMS R atom Metallic Reduction properties increase Alkaline earth metals Basic character (excl. Be - amphoteric) Formula of higher oxide of higher hydroxide …ns 2 s. about. +2 RO R(OH)
GENERAL CHARACTERISTICS Be Mg Ca Sr Ba Ra Radius of the atom and Nuclear charge increase Maximum degree Metallic and oxidation reduction +2 Alkaline earth metals The main sv-va Oxides and Hydroxides uv-Xia. Reactive metals, found in nature only in the form of compounds 2 They interact with water to form alkalis. nS
PHYSICAL PROPERTIES OF MAGNESIUM, BERYLLIUM AND ALKALINE EARTH METALS silver-white substances. malleable and plastic, rather soft, although harder than alkaline ones. Beryllium is notable for its considerable hardness and is mostly not cut with a knife (an exception is strontium). and brittleness, barium cracks with a sharp blow. The metal crystal lattice causes their high thermal and electrical conductivity. Metals have melting and boiling points higher than those of alkali metals. Beryllium and magnesium are covered with a strong oxide film and do not change in air. Alkaline earth metals are very active, they are stored in sealed ampoules, under a layer of vaseline oil or
Physical properties of metals II A group density Тmelt 1285 850 651 1. 85 770 710 960 3. 76 2. 63 1. 74 Be 6 1. 54 Mg Ca Sr Ba Ra
th and Soft primary layer of Mg At room temperature, it is covered with the thinnest oxide film.
PHYSICAL PROPERTIES Be Purely pliable, but slight admixtures make it brittle. oxide film
Light, whitish-gray, ductile metal Ca Melting point C Due to sufficient hardness, it is impossible to cut with a knife, like alkali metals
OBTAINING 1. Barium is obtained by oxide reduction: 3 Ba. O + 2 Al \u003d 3 Ba + Al 2 O 3 2. The rest of the metals are obtained by electrolysis of chloride melts: Ca. Cl 2 \u003d Ca + Cl 2 (electronic current)
CHEMICAL PROPERTIES - REDUCERS 1. Form binary compounds with non-metals Reaction with oxygen. All metals form oxides RO, barium can-peroxide - Ba. O 2: Ba + O 2 \u003d Ba. O 2 peroxide Ca + O 2 \u003d Ca. O Ba + S = Ba. S sulfide Ca + H 2 \u003d Ca. H 2 hydride Ca + 2 C \u003d Ca. C 2 carbide 3 Ba + 2 P \u003d Ba 3 P 2 phosphide Ca + N 2 \u003d Ca 3 N 2 nitride Ca + Cl 2 \u003d Ca. Cl 2 chloride
2. Reaction with water. They form alkalis. Under normal conditions, the surface of Be and Mg is covered with an inert oxide film, so they are resistant to water. Ca + 2 H 2 O \u003d Ca (OH) 2 + H 2 (at o.s.) Mg + H 2 O \u003d Mg (OH) 2 + H 2 (at t)
3. All metals dissolve in acids: Ca + 2 HCl = Ca. Cl 2 + H 2 4. With special acids (Be is similar to Al) Ca + HNO 3 (c) \u003d N 2 O + Ca (NO 3) 2 + H 2 O Ca + HNO 3 (p) \u003d NH 4 NO 3 + Ca (NO 3) 2 + H 2 O (N 2 O, NH 3) Ca + H 2 SO 4 (c) = H 2 S + Ca. SO 4 + H 2 O Be passivates with nitric acid, the reaction does not proceed in the cold, regardless of the acid concentration
5. Ca, Mg with oxides of heavy metals Restore metals from their oxides - pyrometallurgy (calcethermy, magnethermy) Ca + Cu. O = Cu + Ca. O(t) 2 Mg + Ti. O 2 → 2 Mg. O + Ti 5 Ca + V 2 O 5 → 5 Ca. O + 2 V 2 Mg + CO 2 → 2 Mg. O + C combustion of Mg in carbon dioxide
6. Qualitative reaction to alkaline earth metal cations - coloring of the flame in the following colors: Ca 2+ - dark orange Sr 2+ - dark red Ba 2+ - light green
CHEMICAL PROPERTIES OF ALKALI METALS GENERALIZATION M E + Cl 2 Chloride phosphide T + P + H 2 + N 2 nitride A + S Sulfide L + O 2 Oxide + C carbide L Ca, Sr, Ba + H 2 O S + acids Hydride Alkali + H 2 salts and hydrogen
INTERACTION WITH WATER Complete the reaction equations, name the reaction products and make up the island in the reaction. Ca + H 2 O Sr + H 2 O Ba + H 2 O
GROUP II METAL OXIDES The general formula of oxides is Me. O and peroxides - Me. O 2 Group IIA metal oxides are basic oxides, Be. O exhibits amphoteric properties.
COMPOUNDS OF ALKALINE EARTH METALS Oxides of alkaline earth metals General MO formula Type and class Basic oxide of substances Physical Solid crystalline properties of a white substance Chemical MO + H 2 O \u003d properties MO + acid oxide \u003d MO + acid \u003d
PREPARATION Oxidation of metals (except Ba, which forms peroxide) Ca + O 2 = Ca. O Thermal decomposition of magnesium nitrate or insoluble Ca carbonates. CO 3 → Ca. O + CO 2 t˚C 2 Mg(NO 3)2 → 2 Mg. O + 4 NO 2 + O 2 t˚C
CHEMICAL PROPERTIES 1. With acid oxide 3 Ca. O + P 2 O 5 \u003d Ca 3 (PO 4) 2 2. With water Ca. O + H 2 O \u003d Ca (OH) 2 (except Be. O) 3. With acid Ca. O + HCl = Ca. Cl 2 + H 2 O 4. With amphoteric oxide Ca. O + Zn. O = Ca. Zn. O2
SPECIAL PROPERTIES OF OXIDES 2 Ba. O + O 2 \u003d 2 Ba. O 2 peroxide, only for barium Be. O exhibits amphoteric properties, interacts with alkalis: Be. O+2Na. OH = Na 2 Be. O 2 + H 2 O alloy Be. O+2Na. OH + H 2 O \u003d Na 2 Be solution. O + Na 2 CO 3 \u003d Na 2 Be. O 2 + CO 2 alloy
Alkaline earth metal compounds ALKALINE EARTH METAL HYDROXIDES General formula M(OH)2 Type and class of substances Alkalis Physical properties Chemical properties White crystalline solids with an ionic crystal lattice M(OH)2 + salt = M(OH)2 + acid oxide =
HYDROXIDES OF ALKALINE EARTH METALS - ALKALI. R (OH) 2 hydroxides are white crystalline substances, less soluble in water than alkali metal hydroxides (the solubility of hydroxides decreases with decreasing serial number; Be (OH) 2 is insoluble in water, soluble in alkalis). The basicity of R (OH) 2 increases with increasing atomic number: Be (OH) 2 - amphoteric hydroxide Mg (OH) 2 - weak base Ca (OH) 2 - alkali; other hydroxides are strong bases (alkalis).
OBTAINING HYDROXIDES 1. Reactions of alkaline earth metals or their oxides with water: Ba + 2 H 2 O Ba(OH) 2 + H 2 Ca. O + H 2 O Ca(OH)2 2. Electrolysis of Ca salt solutions. Cl 2 + H 2 O Ca (OH) 2 + Cl 2 + H 2 el. current 3. Be(OH)2 and Mg(OH)2 are produced by Be exchange reactions. Cl 2 + 2 Na. OH = 2Na. Cl + Be(OH)2
CHEMICAL PROPERTIES 1. change the color of the indicator Litmus - blue Methyl orange - yellow Phenolphthalein - raspberry Hydroxides of alkaline earth metals in water dissociate into
CHEMICAL PROPERTIES 2. Reactions with acidic oxides: Ca(OH)2 + SO 2 Ca. SO 3 + H 2 O Ba (OH) 2 + CO 2 Ba. CO 3 + H 2 O Ca (OH) 2 + 2 CO 2 CA (HCO 3) 2 Ca (OH) 2 + CO 2 \u003d Ca. CO 3 + H 2 O Qualitative reaction to carbon dioxide 3. Reactions with acids (neutralization) Ba (OH) 2 + 2 HNO 3 Ba (NO 3) 2 + 2 H 2 O 4. Exchange reactions with salts: Ba (OH) 2 + K 2 SO 4 Ba. SO 4+ 2 KOH
CHEMICAL PROPERTIES 5. With amphoteric metals, oxides, hydroxides Ca(OH)2 + Be(OH)2 Ca (solution) Ca(OH)2 + Be(OH)2 Ca. be. O 2 + H 2 O (alloy) Ca (OH) 2 + Be. O + H 2 O Ca (solution) Ca (OH) 2 + Be. About Ca. be. O 2 + H 2 O (alloy) Ca (OH) 2 + Be Ca + H 2 calcium tetrahydroxoberyllate
TRIVIAL NAMES OF SUBSTANCES Ca. O - quicklime Ca(OH)2 -slaked lime (lime water, milk) Ca. CO 3 - chalk, marble, limestone Ca. SO 4 * 2 H 2 O - gypsum Ca (Cl. O) Cl - bleach
SALT OF ALKALINE EARTH METALS Soluble salts of Be and Ba are toxic, poisonous! The Ba 2+ cation is usually opened by an exchange reaction with sulfuric acid or its salts: Barium sulfate is a white precipitate, insoluble in mineral acids
CALCIUM IN NATURE Calcium rocks - limestone, marble, chalk. Remember the formula of these rocks. What is their difference?
CHALK, LIMESTONE, MARBLE DO NOT DISSOLVE IN PURE WATER, BUT ARE SOLUBLE IN ACID SOLUTIONS, EVEN SO WEAK AS NATURAL WATER. When water seeps from the surface of the earth through limestone deposits, the following processes occur: 1. sinkholes form if the rock lies under a thin layer of soil
2. If the rocks lie at great depths, underground karst caves appear. What is the name of the deposits hanging in the form of giant icicles from the roof of the cave? And the columns growing towards them from the bottom of the cave? What chemical reactions take place?
LIMESTONE AND MARBLE ARE USED IN ARCHITECTURE AND SCULPTURE Under the influence of acid rain, buildings are destroyed. What reactions take place?
CALCIUM IN THE HUMAN BODY The mineral containing calcium phosphate plays an important role in the human body. It is the building material of human bones, is part of the enamel. In combination with other minerals, it supports the functioning of the cardiovascular system, prevents the occurrence of colon cancer, regulates nerve function, and helps lower cholesterol. The body of an adult contains more than 1 kg of calcium in the form of Ca 3 (PO 4) 2.
Ca. SO 4 - calcium sulfate, occurs in nature in the form of the mineral gypsum Ca. SO 4 * 2 H 2 O, which is a crystalline hydrate. It is used in construction, medicine for applying fixed plaster bandages, for making casts. For this, semi-aqueous gypsum 2 Ca is used. SO 4 - alabaster.
BERYLLIUM Beryllium is similar to aluminum and magnesium… It got its name because it is found in the mineral beryl. The metal is also called glycium from the Greek word "sweet", because its salts have a sweetish taste. D. I. Mendeleev
BERYLLIUM COMPOUNDS IN NATURE Chrysoberyl Be. Al 2 O 4 Emerald Aquamarine Alexandrite
“The emerald is capricious, like a woman, it is not found where it is looked for.” Thanks to its rich green color and hardness, it is very popular with jewelers, the wonderful color is caused by the presence of chromium or vanadium ions. “It seems that if you look into aquamarine, you will see a quiet sea with water the color of stars” K. G. Paustovsky This color is given to it by a small admixture of ferrous iron
MAGNESIUM IN NATURE Magnesium is part of the active center of the green pigment of plants - chlorophyll Automotive, aviation and rocket industry Magnalium is a hard and durable alloy with aluminum - 30% Mg with zinc additives,
MAGNESIUM IN MEDICINE In medicine, magnesium carbonate and magnesium oxide are used as a means of neutralizing the hydrochloric acid of the stomach and as mild laxatives (Gastal, Rennie, Almagel). Magnesium sulfate ("epsom salt") is used as a laxative, choleretic and analgesic for spasms of the gallbladder. A solution of magnesium sulphate is administered as an anticonvulsant for epilepsy and as an antispastic drug for urinary retention, bronchial asthma, and hypertension. organic magnesium salts are used in the manufacture of dietary supplements and drugs with a wide range of therapeutic and prophylactic effects, such as
WATER HARDNESS Water hardness is a set of chemical and physical properties of water related to the content of dissolved salts of alkaline earth metals, mainly calcium and magnesium (the so-called “hardness salts”) in it. Consumption of hard or soft water is not usually harmful to health, there is evidence that high hardness contributes to the formation of urinary stones, and low hardness slightly increases the risk of cardiovascular disease. The taste of natural
HARDNESS OF WATER Hard water dries the skin when washing, it does not foam well when using soap. The use of hard water causes deposits (scale) to appear on the walls of the boilers, in pipes, etc. At the same time, the use of too soft water can lead to corrosion of the pipes. The hardness of natural waters can vary within fairly wide limits and is not constant throughout the year. Hardness increases due to evaporation of water, decreases during the rainy season, as well as during the melting of snow and ice.
WATER HARDNESS Types of water hardness Present ions Ways to eliminate water hardness Temporary (carbonate) Ca(2+), Mg(2+) HCO 3(-) 1. Boiling 2. Adding soda or Ca(OH)2 Constant Ca(2+) , Mg(2+) SO 4(2 -) 1. Addition of soda. 2. Use of cation exchangers Total Ca(2+), Mg(2+), HCO 3(-), Cl(-) SO 4(2 -) A combination of all the above methods.
STRONTIUM IN NATURE Class Sarcodidae - radiolarians, have radically located pseudopodia. The mineral skeleton, consisting of silica or strontium sulfate, takes the form of regular geometric shapes (balls, polyhedra, rings) consisting of individual needles.
APPLICATION OF STRONTIUM SALTS As a collection mineral, celestite is highly valued, but is practically not used in jewelry because of its low hardness and high brittleness. Characteristic samples of celestine are blue, light blue, gray-blue and slightly bluish; celestine can be colorless, as well as white, yellowish, bluish-green, reddish, brown, sometimes barely translucent, sometimes with zonal color.
USE OF STRONTIUM SALTS Strontium compounds have been used in pyrotechnics; it is worth throwing a pinch of strontium salt into the flame - and it will turn red. All the red fireworks and flare lights are all thanks to strontium. Strontium compounds are used in the glass and ceramic industries to obtain glazed surfaces,
THE SECRETS OF CELESTINE Herr Heinemann was content with his life. He was doing well, very well indeed, when compared with many other emigrants who moved to the United States. His winery on a beautiful lake island prospered, and now, it took to make a small well for the needs of production. Since yesterday, his assistants have been doing this, hollowing out the rock. And today one of them came running, they say, it’s better for him to look for himself. Eh, you have to do everything yourself. Herr Heinemann went down to the cellar where work was going on. - Well, what do you have here? - Here, look, mister, they were chiseling a stone and stumbled upon a void ... - Give me a lantern. Herr Heinemann descended into a hole in the rock - the result of a day's work. There was indeed a gaping hole at the bottom of it. He leaned over and shone his flashlight inward. And he could not believe his eyes: the light of the lantern snatched out the walls of a vast cave, covered with huge bluish-white crystals. Herr Heinemann had already decided that this was an underground treasure trove of trolls from the fairy tales of his homeland, but there are no German trolls in the USA. Herr Heinemann chuckled at his own logic.
GENETIC SERIES OF CALCIUM Ca. About Ca (OH) 2 Ca. CO 3 Ca (HCO 3) 2 Write the reaction equations with which you can carry out the transformation of substances.
CHAIN OF TRANSFORMATIONS Ca → Ca. O → Ca. Cl 2 → Ca (OH) 2 → Ca. CO 3 →Ca. O For reactions, make ionic equations and ox-reduction balances.
To the family alkaline earth elements include calcium, strontium, barium and radium. D. I. Mendeleev included magnesium in this family. Alkaline earth elements are named for the reason that their hydroxides, like alkali metal hydroxides, are soluble in water, that is, they are alkalis. “... They are called earthy because in nature they are found in the state of compounds that form an insoluble mass of the earth, and themselves, in the form of RO oxides, have an earthy appearance,” Mendeleev explained in Fundamentals of Chemistry.
General characteristics of the elements of group IIa
Metals of the main subgroup of group II have an electronic configuration of the external energy level ns², and are s-elements.
Easily donate two valence electrons, and in all compounds they have an oxidation state of +2
Strong reducing agents
The activity of metals and their reducing ability increases in the series: Be–Mg–Ca–Sr–Ba
Alkaline earth metals include only calcium, strontium, barium and radium, less often magnesium
Beryllium is closer to aluminum in most properties.
Physical properties of simple substances
Alkaline earth metals (compared to alkali metals) have higher t°pl. and t ° boiling., ionization potentials, densities and hardness.
Chemical properties of alkaline earth metals + Be
1. Reaction with water.
Under normal conditions, the surface of Be and Mg is covered with an inert oxide film, so they are resistant to water. In contrast, Ca, Sr and Ba dissolve in water with the formation of alkalis:
Mg + 2H 2 O - t ° → Mg (OH) 2 + H 2
Ca + 2H 2 O → Ca (OH) 2 + H 2
2. Reaction with oxygen.
All metals form oxides RO, barium peroxide - BaO 2:
2Mg + O 2 → 2MgO
Ba + O 2 → BaO 2
3. Form binary compounds with other non-metals:
Be + Cl 2 → BeCl 2 (halides)
Ba + S → BaS (sulfides)
3Mg + N 2 → Mg 3 N 2 (nitrides)
Ca + H 2 → CaH 2 (hydrides)
Ca + 2C → CaC 2 (carbides)
3Ba + 2P → Ba 3 P 2 (phosphides)
Beryllium and magnesium react relatively slowly with non-metals.
4. All alkaline earth metals dissolve in acids:
Ca + 2HCl → CaCl 2 + H 2
Mg + H 2 SO 4 (dec.) → MgSO 4 + H 2
5. Beryllium dissolves in aqueous solutions of alkalis:
Be + 2NaOH + 2H 2 O → Na 2 + H 2
6. Volatile compounds of alkaline earth metals give the flame a characteristic color:
calcium compounds - brick red, strontium - carmine red, and barium - yellowish green.
Beryllium, like lithium, is an s-element. The fourth electron that appears in the Be atom is placed in the 2s orbital. The ionization energy of beryllium is higher than that of lithium due to the larger nuclear charge. In strong bases, it forms the BeO 2-2 beryllate ion. Therefore, beryllium is a metal, but its compounds are amphoteric. Beryllium, although a metal, is much less electropositive than lithium.
The high ionization energy of the beryllium atom differs markedly from other elements of the PA subgroup (magnesium and alkaline earth metals). Its chemistry is largely similar to that of aluminum (diagonal similarity). Thus, this is an element with the presence of amphoteric qualities in its compounds, among which the basic ones still prevail.
The electronic configuration of Mg: 1s 2 2s 2 2p 6 3s 2 has one significant feature compared to sodium: the twelfth electron is placed in the 2s orbital, where there is already 1e - .
Magnesium and calcium ions are indispensable elements of the vital activity of any cell. Their ratio in the body must be strictly defined. Magnesium ions are involved in the activity of enzymes (for example, carboxylase), calcium - in the construction of the skeleton and metabolism. Increasing the calcium content improves the absorption of food. Calcium excites and regulates the work of the heart. Its excess sharply increases the activity of the heart. Magnesium plays part of the role of a calcium antagonist. The introduction of Mg 2+ ions under the skin causes anesthesia without a period of excitement, paralysis of muscles, nerves and heart. Getting into the wound in the form of metal, it causes long-term non-healing purulent processes. Magnesium oxide in the lungs causes the so-called foundry fever. Frequent contact of the skin surface with its compounds leads to dermatitis. The most widely used calcium salts in medicine are CaSO 4 sulfate and CaCL 2 chloride. The first is used for plaster casts, and the second is used for intravenous infusions and as an internal remedy. It helps fight swelling, inflammation, allergies, relieves spasms of the cardiovascular system, and improves blood clotting.
All barium compounds except BaSO 4 are poisonous. Cause mengoencephalitis with damage to the cerebellum, damage to smooth heart muscles, paralysis, and in large doses - degenerative changes in the liver. In small doses, barium compounds stimulate the activity of the bone marrow.
When strontium compounds are introduced into the stomach, its disorder, paralysis, and vomiting occur; lesions are similar in signs to lesions from barium salts, but strontium salts are less toxic. Of particular concern is the appearance in the body of the radioactive isotope of strontium 90 Sr. It is extremely slowly excreted from the body, and its long half-life and, therefore, the duration of action can cause radiation sickness.
Radium is dangerous for the body with its radiation and a huge half-life (T 1/2 = 1617 years). Initially, after the discovery and production of radium salts in a more or less pure form, it began to be used quite widely for fluoroscopy, the treatment of tumors, and some serious diseases. Now, with the advent of other more accessible and cheaper materials, the use of radium in medicine has practically ceased. In some cases, it is used to produce radon and as an additive to mineral fertilizers.
The filling of the 4s orbital is completed in the calcium atom. Together with potassium, it forms a pair of s-elements of the fourth period. Calcium hydroxide is a fairly strong base. In calcium - the least active of all alkaline earth metals - the nature of the bond in the compounds is ionic.
According to its characteristics, strontium occupies an intermediate position between calcium and barium.
The properties of barium are closest to those of alkali metals.
Beryllium and magnesium are widely used in alloys. Beryllium bronzes are elastic copper alloys with 0.5-3% beryllium; aviation alloys (density 1.8) contain 85-90% magnesium ("electron"). Beryllium differs from other metals of group IIA - it does not react with hydrogen and water, but it dissolves in alkalis, since it forms amphoteric hydroxide:
Be + H 2 O + 2NaOH \u003d Na 2 + H 2.
Magnesium actively reacts with nitrogen:
3 Mg + N 2 \u003d Mg 3 N 2.
The table shows the solubility of hydroxides of elements of group II.
Traditional technical problem - hardness of water associated with the presence of Mg 2+ and Ca 2+ ions in it. Magnesium and calcium carbonates and calcium sulfate are deposited on the walls of heating boilers and pipes with hot water from bicarbonates and sulfates. They especially interfere with the work of laboratory distillers.
S-elements in a living organism perform an important biological function. The table shows their content.
The extracellular fluid contains 5 times more sodium ions than inside the cells. An isotonic solution ("physiological fluid") contains 0.9% sodium chloride, it is used for injections, washing wounds and eyes, etc. Hypertonic solutions (3-10% sodium chloride) are used as lotions in the treatment of purulent wounds ("stretching » pus). 98% of potassium ions in the body are inside the cells and only 2% in the extracellular fluid. A person needs 2.5-5 g of potassium per day. 100 g of dried apricots contains up to 2 g of potassium. In 100 g of fried potatoes - up to 0.5 g of potassium. In intracellular enzymatic reactions, ATP and ADP participate in the form of magnesium complexes.
Every day a person needs 300-400 mg of magnesium. It enters the body with bread (90 mg of magnesium per 100 g of bread), cereals (in 100 g of oatmeal up to 115 mg of magnesium), nuts (up to 230 mg of magnesium per 100 g of nuts). In addition to building bones and teeth based on hydroxylapatite Ca 10 (PO 4) 6 (OH) 2, calcium cations are actively involved in blood coagulation, transmission of nerve impulses, and muscle contraction. Adults need to consume about 1 g of calcium per day. 100 g of hard cheeses contain 750 mg of calcium; in 100 g of milk - 120 mg of calcium; in 100 g of cabbage - up to 50 mg.
