周期表の化学！ 102番元素ノーベリウムは「軟らかい」！？ ―重い元素に働く相対論効果がもたらす新しい性質―

2026-10-01 大阪大学

クラウンエーテルと相互作用するノーベリウムの分子構造イメージ

＜関連情報＞

• https://www.sci.osaka-u.ac.jp/ja/topics/17271/
• https://www.science.org/doi/10.1126/sciadv.aeh4903

102 No 2+ を軟質金属イオンとして用いる場合：クラウンエーテルを用いた255 Noの抽出 102No2+ as a soft metal ion: Extraction of 255No using crown ethers

Eisuke Watanabe, Ruilin Wang, Takuya Yokokita, Ryohei Nakanishi, […] , and Yoshitaka Kasamatsu
Science Advances  Published:30 Sep 2026
DOI:https://doi.org/10.1126/sciadv.aeh4903

Abstract

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, No²⁺ exhibits similar behavior to alkaline earth metal ions, particularly Ca²⁺ and Sr²⁺, suggesting hard-acid character. In this study, the soft metal ion behavior of No²⁺ was demonstrated through complex with crown ethers. In the solid–liquid extraction of ²⁵⁵No using di-^tBu-dicyclohexano-18-crown-6 in HNO₃, No²⁺ was extracted as much as Sr²⁺. Density functional theory calculations confirmed higher stability of the No²⁺–DtBuCH18C6 complex, with covalent bonding involving the 6d orbitals. Theoretical studies also revealed strong relativistic effects on the atomic orbitals of No²⁺, rendering No²⁺ a soft ion similar to Pb²⁺.