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Elemental classification Lewis acid/base Pearson’s hard/soft metals Ionic and covalent index

Explore the elemental classification, Lewis acid/base reactions, and equilibrium reactions of trace metals like Pb, Cd, Cu, and Zn in soils. Gain knowledge about their common minerals and aqueous species. Use log activity-pH graphs to understand their behavior.

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Elemental classification Lewis acid/base Pearson’s hard/soft metals Ionic and covalent index

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  1. Trace metals review • Elemental classification • Lewis acid/base • Pearson’s hard/soft metals • Ionic and covalent index • Ionic potentials • Electron negativity • Earth Scientist's Periodic Table of the Elements and Their Ions • Know common minerals and aqueous species in soils - Pb, Cd, Cu and Zn • Familiar with equilibrium reactions • Use log activity-pH graphs

  2. /metal /metal low En, large size, high polarization, easily oxidized Adriano (2001) HSAB-the 13th most cited paper in JACS

  3. CaCO3 + 2 H+ Ca2+ + CO2 + H2O log(Ca2+) = log k° - 2 pH – log (CO2) Lindsay, 1979

  4. PbO + 2H+ < -- > Pb2+ + H2O K° = (Pb2+)/(H+)2 log K° = log (Pb2+) - 2 log (H+) log K° = log (Pb2+) + 2 pH log (Pb2+) = log K° - 2 pH PbSO4 < -- > Pb2+ + SO42- K° = (Pb2+)*(SO42-) log K° = log (Pb2+) + log (SO42-) log (Pb2+) = log K° - log (SO42-)

  5. PbCO3 + 2 H+ Pb2+ + CO2 + H2O log(Pb2+) = log k° - 2 pH – log (CO2) Pb5(PO4)3Cl+ 6 H+ 5Pb2+ + 3 H2PO4- + Cl- log (Pb2+)= 1/5 [log K° - 6 pH –3 log (H2PO4-) - log (Cl- )]

  6. Use log activity-pH graphs Pb5(PO4)3Cl + 6 H+ 5Pb2+ + 3 H2PO4- + Cl- log (Pb2+) = 1/5 [log K° - 6 pH – 3 log (H2PO4-) - log (Cl- )] Log (Cl-) = -3 M Ca5(PO4)3OH + 8 H+ 5Ca2+ + 3 H2PO4- + H2O Hydroxyapatite log (H2PO4-) = 1/3 [log K° - 8 pH – 5 log (Ca2+)] Soil-Ca = 10 -2.5 M Log (Ca2+) = -2.5 M CaCO3 + 2 H+ Ca2+ + CO2 + H2O log(Ca2+) = log k° - 2 pH – log (CO2)

  7. Use log activity-pH graphs Pb2+  H2PO4- Ca5(PO4)3OH FePO4 Soil-Ca CaCO3 Soil-Fe

  8. Pb5(PO4)3Cl+ 6 H+ 5Pb2+ + 3 H2PO4- + Cl- log (Pb2+)= 1/5 [log K° - 6 pH –3 log (H2PO4-) - log (Cl- )]

  9. Adriano (2001)

  10. Pb2+ + 4OH- < -- > Pb(OH)42- K = (Pb(OH)42-)/(Pb2+)*4(OH-) log K = log (Pb(OH)42-) - 2 log (Pb2+) + 4 pH log (Pb(OH)42-) = log K - 2 log (Pb2+) + 4 pH

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