Redox reactions for Group 5 elements, including element 105, in aqueous solutions

Standard redox potentials E-degrees(M(z+x)/M(z+)) in acidic solutions for group 5 elements including element 105 (Ha) and the actinide, Pa, have been estimated on the basis of the ionization potentials calculated via the multiconfiguration Dirac-Fock method. Stability of the pentavalent state was shown to increase along the group from V to Ha, while that of the tetra- and trivalent states decreases in this direction. Our estimates have shown no extra stability of the trivalent state of hahnium. Element 105 should form mixed-valence complexes by analogy with Nb due to the similar values of their potentials E-degrees(M3+/M2+). The stability of the maximum oxidation state of the elements decreases in the direction 103 > 104 > 105.