6533b861fe1ef96bd12c5642

RESEARCH PRODUCT

The hydration enthalpies of Md3+ and Lr3+

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description

Lawrencium (3-min 260Lr) and lighter actinides were produced in the bombardment of a 249Bk target with 18O ions and loaded onto a cation exchange column in 0.05 M α-hydroxyisobutyrate solution at pH=4.85, together with the radioactive lanthanide tracers 166Ho, 171Er and 171Tm. In elutions with 0.12 M α=hydroxyisobutyrate solution (pH=4.85), trivalent Lr was eluted exactly together with the Er tracer and Md was eluted close to Ho. Lr elutes much later than expected based on the known elution positions of the lighter actinides and the expected analogy to the elution positions of the homologous lanthanides. From the measured elution positions, ionic radii were calculated for Lr3+ and Md3+. Semi- empiricalmodels allow the calculation of the heat of hydration from the ionic radii, resulting in ΔHhyd≈-−3654 kJ/mol for Md3+ and ΔHhyd≈ -−3685 kJ/mol for Lr3+.