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An overview of the occurrence, properties, synthesis, technical applications, and alkaline earth metal salts of the alkaline earth metals Be, Mg, Ca, Sr, and Ba. It includes information on their atomic structure, electronic configuration, electronegativity, ionization energy, ionic radius, melting and boiling points, density, flame coloring, and hydration of the alkaline earth cations.
Typology: Exercises
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Group2 or IIA^4 Be^12 Mg^20 Ca^38 Sr^56 Ba^88 Ra „Alkaline earth metals“
Beryllium (beryllos)^ BeAl[SiO^326
]^ Beryl, emerald, aquamarine 18 greek: Beryll^ Al[BeO]^24
ChrysoberylBeSiOPhenakite 24 Magnesium (magnesia)^ (Ca,Mg)CO
Dolomite 3 town in Asia Minor^ (Mg,Fe)[SiO
]^ Olivine (^4) Mg(OH) [SiO] Talc (^32410) MgAlOSpinel 24 Calcium (calx)^ CaSO^4
Gypsum latin: lime^ CaCO^3
Calcite, aragoniteCaFFluorite (^2) Ca (PO) (OH,F) Apatite 543 Strontium (strontian)^ SrSO^4
Cölestine Place in Scotland^ SrCO^3
Strontianite Barium (barys)^ BaSO^4
Barite greek: heavy^ BaCO^3
Witherite
(g) + C(s)^ ^ MgCl(s) + CO(g) 22 Calcium, StrontiumBy fused-salt electrolysis of the chlorides mixed with the fluorides (eutectic)BariumBy reduction of BaO with Al or Si at 1200 °C in vacuum3 BaO(s) + 2 Al(s)^ ^ AlO(s) + 3 Ba(g)^23 3 BaO(s) + Si(s)^ ^ BaSiO(s) + 2 Ba(g)^3 BaO is obtained by thermal decomposition of BaCO
^ BaO + CO 3 2
moderator and reflector for neutrons
-^ Low density^ ^ emission windows for x-ray sources •^ Be-Cu-alloys^ ^ good conductivity and a hardness comparable to that of steel •^ Be-Ni-alloys^ ^ watch spring and surgical instrumentsMagnesium^3 •^ Density = 1.74 g/cm^ Mg-alloys as light metals in the aviation and automotive industry •^ Energy source of the future?: 2 Mg(s) + O
(^0) (g) ⇌ 2 MgO(s) H= -1204 kJ/mol 2 R^ Calcium, Strontium and Barium •^ Calcium is used as a reduction agent in metallurgy •^ Ba is used as getter material in cathode ray tubes and discharge lamps •^ The mixed oxide BaO/SrO/CaO reacts with tungsten at high temperatures and is used asthermionic electron emitter:BaO + W^ ^ BaWO+ 3 Ba (good thermal e^36
-^ -emitter) -^ BaO is used as a additive in glasses to increase the cross-section for x-rays •^ CaO shows white^ ^ thermo-luminescence “limelight”
Sulphate 2+^ .MgMgCl6HO^22
..Mg(NO) 6HO^ MgSO7HO 32242 2+^ .Ca CaCl6HO^22
..Ca(NO) 4HO^ CaSO2HO 32242 2+^ .SrSrCl6HO^22
.Sr(NO) 4HO^ SrSO 3224 2+^ .BaBaCl2HO^22 Ba(NO)^ BaSO^32 Enthalpy of solution = hydration enthalpy – lattice enthalpyEntropy of solution = hydration entropy – lattice entropyFree enthalpy of solution = enthalpy of solution – T*entropy of
solution (^000) i.e. G=^ H– T*S^ L^ L^ L
2+^ - M (g) + 2 X(g) HydrationLatticeenthalpyenthalpyEnthalpy+^ - M^ (aq) + 2 X(aq)Enthalpy of solutionMX(s) 2 2+^ - M^ (g) + 2 X(g) HydrationLatticeentropyentropyEntropy+^ - M^ (aq) + 2 X(aq)Entropy of solutionMX(s) 2
(^0) H< 0^0 TS^ > 0 Poor solubility^00 Free enthalpy of solution^ G=^ H– T*L^ L^
(^0) H> 0^0 TS^ < 0 Example MgCl^2 Lattice enthalpy [kJ/mol] Hydration enthalpy [kJ/mol]
Enthalpy of solution [kJ/mol] -2523^ -^
Lattice entropy [J/Kmol]^ Hydration entropy [J/Kmol]
Entropy of solution [J/Kmol] 360 -^
(^0) Free enthalpy of solution G= -154 kJ/mol – 298 K*(-115 J/Kmol) = - 120 kJ/molL^ (at room temperature = 298 K)
MgClfor the drying of gases^ ^ forms hexahydrates^2 Compounds with oxygen2 Mg(s) + O(g)^ ^ MgO(s) “magnesia“^2
(^0) H= -1204 kJ/molR^ 2 Mg(s) + CO(g)^ ^ MgO(s) + C(s)^2
(^0) H= -808 kJ/molR^ MgO is used as a neutralisation agent, crucible and oven material as well as a coating forfront panels of plasma displays due to its high emission intensity of secondary electronsMgCl(s) + Ca(OH)^ (s)^ ^ Mg(OH)^ (s) + CaCl^222
(s) 2 2+.Mg-solution + MeCO^ 4 MgCOMg(OH)^23
. 4HO “magnesia alba“ 22
Structure of calcite Lime stone Foraminifers Ca(HCO) (readily soluble) 2 32
Slide
2+ ^ Application of MgS:Eu, CaS:Eu, or SrS:Eu as radiation converters
„Luminescence through doping“
-^ Chordata and vertebrata –^ Cephalopoda
H^ O^2 TO 2 C + 2-H SO^4 TH O 2 2-CO 3 H^ SO^24 -H 2 CO (^2) -H O 2