102 No 2+ as a soft metal ion: Extraction of 255 No using crown ethers

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The chemical properties of transfermium elements with atomic numbers >100 are largely unknown. Element 102, nobelium, is an actinide and forms stable +2 valent cations in aqueous solutions, unlike other heavy actinide. In previous experiments, No 2+ exhibits similar behavior to alkaline earth metal ions, particularly Ca 2+ and Sr 2+ , suggesting hard-acid character. In this study, the soft metal ion behavior of No 2+ was demonstrated through complex with crown ethers. In the solid–liquid extraction of 255 No using di- t Bu-dicyclohexano-18-crown-6 in HNO 3 , No 2+ was extracted as much as Sr 2+ . Density functional theory calculations confirmed higher stability of the No 2+ –DtBuCH18C6 complex, with covalent bonding involving the 6 d orbitals. Theoretical studies also revealed strong relativistic effects on the atomic orbitals of No 2+ , rendering No 2+ a soft ion similar to Pb 2+ .