31. BERYLLIUM, MAGNESIUM AND ALKALINE EARTH METALS.

Metals belong to the main subgroup of the second group: beryllium, magnesium, calcium, strontium, barium, radium.

STAY IN THE NATURE

Contains in crust beryllium - 0,00053%, magnesium - 1,95%, calcium - 3,38%, strontium - 0,014%, barium - 0,026%, radium - artificial element. Meet in the nature only in the form of connections - silicates, aluminosilicates, carbonates, phosphates, sulfates, etc. The major mineraly:mgco3 - magnesite, MgCO3 · CaCO3 - dolomite, MgCl2 · 6H2O - bischofite, CaCO3 - chalk, marble, limestone, CaSO4 · 2H2O - gypsum, CaF2 - fluorite, 3Ca3(PO4) 2 · CaF2 - fluorapatite.

Physical properties of metals

Element	Beryllium Be	Magnesium Mg	Calcium Ca	Strontium Sr	Barium Ba	Radium Ra
Property
Order number of element	4	12	20	38	56	88
Relative atomic mass	9,012	24,305	40,078	87,62	137,328	226
Temperature of melting, C0	1280	650	851	770	710	700
Temperature of boiling, C0	2967	1102	1437	1365	1637	1140
G/cm3 density	1,86	1,75	1,55	2,64	3,61	6
Oxidation levels	+2	+2	+2	+2	+2	+2
Coloring of flame			dark orange	dark red	light green	dark red
Primeneiye of metals	Decelerator of neutrons, additive in special steel, is part бронз	pirotekh- nickname, aircraft industry, electrochemical protection	receiving rare metals is part of alloys	strontium salt phosphors	gazopoglo-titelv electronic beam tubes	rentgeno- diagnostics, research works

RECEIVING

Since metals of this subgroup strong reducers, receiving it is possible only by electrolysis of fusions of salts. In case of Sa usually use CaCl2 (with CaF2 additive for decrease in temperature of melting) CaCl2=Ca+Cl2

 

CHEMICAL PROPERTIES Sa and Mg (M = Sa, Mg)
1. With oxygen	2M+O2=2MO
2. With halogens	M+Cl2=MCl2
3. With sulfur when heating	M+S=MS (sulfide)
4. Lithium interacts with nitrogen	3M+N2=M3N2 (nitride)
5. With hydrogen when heating	M+H2=MH2 (hydride)
6. With water	M+2H2O=M (OH)2+H2

 

WATER HARDNESS
Water hardness is caused by existence in water of soluble salts Ca2+, Mg2 +, etc. Causes scaling. In hard water soap badly forms lather: 2C17H35COONa+Ca2+ =Ca(C17H35OO)2+2Na +
carbonate - temporary	not carbonate - non-constant
Ca(HCO3)2, Mg(HCO3)2, Fe(HCO3)2	CaCl2, CaSO4, MgCl2, MgSO4, etc.
Rigidity elimination
boiling Ca(HCO3)2=CaCO3+CO2+H2O soda addition Ca(HCO3)2+Na2CO3=CaCO3+2NaHCO3	soda addition CaCl2+Na2CO3=CaCO3+2NaCl MgSO4+Na2CO3=MgCO3+Na2SO4

Information on other chemical elements of this group: about beryllium, about strontium, bohrium and radium.

  

 

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