Arsenic Cad- mium Chro- mium Copper Lead Nickel Zinc As Cd Cr Cu Pb Ni Zn Atomic weigth g/mole 74,9 112,4 52,0 63,5 207,2 58,7 65,4 Aqueouss pecies I H3AsO3 H2AsO3^- Cd⁺⁺ Cr⁺⁺⁺ Cu⁺⁺ Pb⁺⁺ Ni⁺⁺ Zn⁺⁺ Oxidation state III II III II II II II Aqueous species II H2AsO4^- HAsO4^-- None HCrO4^- CrO4^-- None None None None Oxidation state V VI - - - -