Life science

Co-precipitation of single atoms of element 104
rutherfordium with samarium hydroxide
Department of Chemistry, Graduate School of Science
Professor Yoshitaka Kasamatsu
https://researchmap.jp/kasamatsu_san?lang=en

Life science

Abstract
All superheavy elements (SHEs), with atomic numbers (Z) ≥104, have been artificially synthesized one atom at a time and theirchemical properties are largely unknown. Because these heavy
nuclei have short lifetimes and their production rates are extremely
low, chemical experiments need to be carried out on single atoms
and the methodologies have mostly been limited to adsorption andextraction. We have now investigated the precipitation properties ofthe SHE Rf (Z = 104). A co-precipitation method with samarium hydroxide previously established had shown that the co-precipitation
behavior of a range of elements reflected these elements’ tendency
to form hydroxide and ammine complexes. Here, co-precipitation
behavior of Rf was investigated in basic solutions (NH3aq and NaOHsolutions). Comparisons between the behavior of Rf with that of Zrand Hf (lighter homologues of Rf) and actinide Th (a pseudo-homologue of Rf) showed that Rf does not coordinate strongly with NH3,
but forms a hydroxide (co)precipitate as the group 4 elements form
M(OH)4 precipitates.

interactions) and quantum electrodynamics, is crucial for a complete understanding of the element properties. Full-relativistic calculations on various chemical behaviors of SHEs that are strongly
influenced by the relativistic effects would advance research on
the relativistic effects. To experimentally observe their new chemical behaviors and to provide such data for the latest relativistic
calculations are of significant importance. By using the presently
developed co-precipitation method, we are planning to investigate
various precipitation behaviors for SHEs.

▍ Background & Results
In heavy atoms, the relativistic effects caused by the high nuclear
charge are strong, and the strong effects stabilize the inner orbital
electrons (s and p1/2) and destabilize the outer orbital electrons (dand f) of SHEs, which would result in characteristic chemical properties among their homologues in the periodic table. Therefore, thechemical properties of SHEs attract many scientists. However, it isdifficult to realize the chemical experiments on SHEs due to single
atom situation in SHE experiments and short half-lives of the heavy
nuclei.
For co-precipitation experiment on element 104, Rf, we previously studied co-precipitation behaviors of its homologous elements,
Zr and Hf, and pseudo homologue, Th. In addition, we developed
an apparatus for rapid and repetitive preparation of co-precipitated samples. In this work, we performed online co-precipitation
experiments using the apparatus for the 261Rf isotope produced inthe 248Cm(18O, 5n)261Rf reaction with the AVF cyclotron at RIKEN.
Co-precipitation yields of Rf were determined as relative values tostandard samples. The values of Rf were around 100% and similar to those of Zr, Hf and Th, which represents that Rf would havethe property to form hydroxide precipitate. In high hydroxide ion
concentration solution, the yield of Rf was different from those of Zrand Hf but similar to that of the pseudo homologue Th.

Fig.1 Schematic figure of online co-precipitation experiment of 261Rf.

▍ Significance of the research and Future perspective
Chemical properties of SHEs may be characteristic in the periodic table due to strong relativistic effects. However, the relativisticeffects are not well understood. The relativistic effects influence
the orbital electrons in all elements though negligibly small for lightelements, and understanding these relativistic effects, as well as
the Coulomb interactions (nucleus-electron and electron-electron

Fig 2. Co-precipitation yields of Zr, Hf, Th, and Rf with samarium hydroxide.

P a t e n t
Tr e a t i s e

Kasamatsu, Yoshitaka; Toyomura, Keigo; Haba, Hiromitsu et al. Co-precipitation behaviour of single atoms of rutherfordium in basic solutions. Nature
Chem. 2021, 13, p. 226-230, doi: 10.1038/s41557-020-00634-6

URLK e y w o r d superheavy element, rf, co-precipitation, precipitate, samarium hydroxide