In theory, most metals should easily corrode in the air. Why? A group of metals called noble metals are relatively difficult to corrode in air. Some noble metals include gold, platinum, and silver. Reference Table 11.1 to come up with a possible reason why the noble metals are relatively difficult to corrode.

Table 11.1

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Half-reaction F₂ +2e2F- Ag²+ + e- → Ag+ Co³+ + e Co²+ H₂O₂ + 2H+ + 2e → 2H₂O Ce4+ + e Ce³+ PbO₂ + 4H+ + SO4² +2e → PbSO4 + 2H₂O MnO4 + 4H+ + 3e → MnO₂ + 2H₂O IO4 + 2H+ + 2e → IO3 + H₂O MnO4 + 8H+ + Se-→ Mn²+ + 4H₂O Au³+ + 3e →→ Au PbO₂ + 4H+ + 2e-→ Pb2+ + 2H₂O Cl₂ +2e2C1- Cr₂O72- + 14H+ + 6e → 2Cr³+ + 7H₂O O₂ + 4H+ + 4e → 2H₂O MnO₂ + 4H+ + 2e- → Mn²+ + 2H₂O IO3 + 6H+ + 5e- → 1₂2 + 3H₂O Br2 + 2e 2Br- VO₂+ + 2H+ + e- → VO²+ + H₂O AuCl + 3e- → Au + 4C1- NO + 2H₂O NO3 + 4H+ + 3e-→ ClO₂ + e-→ ClO₂- 2Hg²+ + 2e → Hg₂²+ 2+ Ag+ + e → Ag Hg₂+ + 2e → 2Hg Fe³+ + e Fe²+ O₂ + 2H+ + 2e- → H₂O₂ MnO4 + e MnO4²- 1₂ +2e 21- Cute Cu 8° (V) 2.87 1.99 1.82 1.78 1.70 1.69 1.68 1.60 1.51 1.50 1.46 1.36 1.33 1.23 1.21 1.20 1.09 1.00 0.99 0.96 0.954 0.91 0.80 0.80 0.77 0.68 0.56 0.54 0.52 Half-reaction O₂ + 2H₂O + 4e¯→ 40H- Cu²+ + 2e →→ Cu Hg₂Cl₂ + 2e → 2Hg + 2Cl- AgCl+eAg + Cl- SO4 + 4H+ + 2e → H₂SO3 + H₂O Cu²+ + e Cu+ 2H+ + 2e Fe³+ + 3e → H₂ Fe Pb²+ + 2e Sn²+ + 2e Ni²+ + 2e PbSO4 + 2e Cd²+ + 2e Fe2+ + 2e →→ Cd →→ Fe Cr²+ Cr³+ + e- Cr³+ + 3e- → Cr Zn²+ + 2e →→→ Zn 2H₂O + 2e →→ H₂ + 2OH- →→Mn Mn2+ + 2e Al³+ + 3e Al H₂ + 2e → 2H- Mg2+ + 2e → Mg La³+ + 3e La →→ Pb Sn →→→ Ni →→ Pb + SO4²- Nate Na Ca2+ + 2e → Ca Ba2+ + 2e-Ba K+ + e → K Lite Li 8° (V) 0.40 0.34 0.27 0.22 0.20 0.16 0.00 -0.036 -0.13 -0.14 -0.23 -0.35 -0.40 -0.44 -0.50 -0.73 -0.76 -0.83 -1.18 -1.66 -2.23 -2.37 -2.37 2.71 -2.76 -2.90 -2.92 -3.05