Download Chapter 12 Group 2: the alkaline earth metals

Chapter 12
Group 2: the alkaline earth metals
Physical Properties
Metals
Halides, oxides, hydroxides, salts of oxoacids
Complex ions in aqueous solution
Complexes with amido or alkoxy ligands
Diagonal relationships
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Radium
http://www.orau.org/PTP/collection/quackcures/radbath.htm
Radium by Gretchen Grove
http://www.rsc.org/chemsoc/visualelements/pages/data/radium_data.html
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Olivine
(Mg,Fe)2SiO4
Dolomite
CaCO3:MgCO3
http://mineral.galleries.com/minera
ls/carbonat/dolomite/dolomite.htm
http://mineral.galleries.com/Minerals/
Silicate/OLIVINE/OLIVINE.htm
Magnesite MgCO3
http://mineral.galleries.com/minerals/
carbonat/magnesit/magnesit.htm
Celestite
SrSO4
Relative abundances in the Earth’s
crust of the alkaline earth metals
http://www.galleries.com/minerals
/sulfates/celestit/celestit.htm
Beryllium
•Small size and high charge density in Be2+
•Be is the only group 2 element that does not form a stable
complex with [EDTA]4-.
•Beryllium compounds tend to be covalent
•Beryllium occurs in the silicate mineral beryl Be3Al2[Si6O18], and
emerald and aquamarine.
Beryl
Emerald
http://mineral.galleries.com/minerals/silicate/beryl/beryl.htm
X-ray Window
http://mineral.galleries.com/minerals/GEMSTONE/EMER http://www.berylliumproducts.com/CommercialXray.aspx
ALD/Emerald.htm
Be3Al2[Si6O18]
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Recycling and magnesium uses
Calcium Uses
World production of CaO, Ca(OH)2, CaO*MgO,
Ca(OH)2*MgO, and Ca(OH)2*Mg(OH)2 is ~125,000 Mt.
CaO(s) + H2O(l)  Ca(OH)2(s)
DrHo = -65 kJ mol-1
Ca(OH)2(s) + CO2(g)  CaCO3(s) + H2O(l)
Hoover Dam
coccolithophore
http://www.esa.int/esaCP/SEMDOG3AR2E_Protecting_1.html
CaF2 + H2SO4  2HF + Ca(HSO4)2
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Physical properties of the group 2 metals, M, and their ions, M2.
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Flame Tests
Ca (orange-red, but pale green when viewed through blue glass)
Sr (crimson, but biolet when viewed through blue glass)
Ba (apple-green)
Radioactive Isotopes of Sr
http://www.inchem.org/documents/ehc/ehc/e25_5.gif
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Metals
Be
Ca
Sr
http://www.americanelements.com/
2Be + O2  2 BeO
Ba
(protective oxide coating)
Mg + 2H2O(g)  Mg(OH)2
+ H2 (g)
M(NH3)  M(NH2) + 4NH3 + H2 (M = Ca,Sr, Ba)
2M + O2 –D
2MO
3M + N2 –D
M3N2
8M + S8 –D 8MS
M + Cl2 –D MX2
Drying Agents and Desiccants
Drying agents for drying or
predrying solvents include
anhydrous MgSO4, CaCl2,
CaSO4, Na2SO4, K2CO3, which
are hygroscopic.
•some can be regenerated by
heating
•some react irreversibly with
H2O (e.g. Ca, Mg, CaH2)
CaH2 + 2 H2O → Ca(OH)2 + 2 H2
Drying agents for use in
desiccators include anhydrous
CaSO4, CaCl2, KOH, P2O5, which
are hygroscopic.
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BeCl2
solid state polymeric structure
BeCl2 in the gas phase
[Be2Cl6]2
Structures of the monomeric group 2 metal dihalides, MX2
Fluorides are sparingly
soluble.
MgF2 Ksp = 7.42x10-11
CaF2 Ksp = 1.46x10-10
SrF2
Ksp = 4.33x10-9
BaF2 Ksp = 1.87x10-7
Slightly more solubility for
larger cations
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[MgBr2(diglyme)(THF)]
Mg
Br
Br
Production of ethyne (acetylene)
CaO + 3C ---2300 K  CaC2 + CO
CaC2 + 2H2O  Ca(OH)2 + C2H2
[MgBr2(THF)2]
Gypsum plasters
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Hydroxides, peroxides, salts of oxoacids
Be(OH2)42+ +2H+, +2H2O ------ Be(OH)2 -----+2OH- Be(OH)42-
MO2  MO + 1/2 O2 (M = Mg, Ca, Sr, Ba)
MgO + H2O2  MgO2 (used in toothpastes)
BeCl2 
[NO]2[Be(NO3)4]  Be(NO3)2 
basic beryllium nitrate
Be4(m4-O)(m-O2NO)6
[Be(OH2)4][O2CC≡CCO2]
Be
Hydrogen bonding in
a beryllium complex
basic beryllium acetate,
[Be4((m4-O)(m-O2CMe)6]
[Sr(OH2)8]2
porphyrin
[Ca2{N(SiMe3)2}2 {m-N(SiMe3)2}2]
chlorophyll a
Ca9(m3-O)8(m-O)8O20
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Diagonal relationships – Li-Mg, Be-Al
CaC2 + N2 ---1300 K  CaNCN + C
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Desulfurization
SO2 + H2O ⇌ H+ + [HSO3]H+ + [HSO3]- + 1/2 O2  2H+ + SO422H+ + SO42- + Ca(OH)2  CaSO4*2H2O
or
2H+ + SO42- +H2O + CaCO3  CaSO4*2H2O + CO2
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