Radiopolarography of mendelevium in aqueous solutions

Abstract

The possible existence of a monovalent ion of mendelevium has been examined further by radiopolarography. Experiments were conducted in several aqueous media with ²⁴¹Am, ²⁴⁹Cf, ²⁵⁴Es, ^255,256Fm and ²⁵⁶Md tracers. Half-wave amalgamation potentials of Md in tetramethylammonium perchlorate and in LiCl were identical within the experimental errors at −1.755 ± 0.005 V vs the saturated calomel electrode, in good agreement with an earlier study by radiocoulometry in an ammonium acetate medium. No shift in the half-wave potential of Md was observed due to NH₄⁺ or Cl⁻ ions; hence, these ions do not act as complexing agents for Md ions present during electrochemical reductions. The shift in the half-wave potential observed in the presence of citrate as a complexing agent was characteristic of the reduction process Md²⁺ → Md⁰(Hg). In noncomplexing media, the slope of the logarithmically transformed wave of Md was ∼ 30 mV, consistent only with a reversible, two-electron reduction process. All of our results provide evidence for electrochemical reduction of the Md²⁺ ion only and disprove the existence of an the intermediate Md⁺ ion in aqueous solution with properties like those of Cs⁺, Ag⁺ or Cu⁺.