Stubelementein

Stubelementein is a hypothetical chemical element with the symbol Sbe and atomic number 153. It is predicted to belong to group 11 of the periodic table, sharing the same group as copper, silver, and gold. The element was first proposed in 2023 by Dr. Anika Müller of the University of Freiburg, who suggested that stubelementein could be synthesized by bombarding a target of the element so far as known, 152‑X, with high-energy neutrons in a particle accelerator. The name derives from the German word “Stube,” meaning "small chamber," referring to the underground laboratories where the experiment was conducted.

Theoretical calculations indicate that stubelementein would have a half‑life of approximately 3.5 seconds, decaying by beta‑minus emission to the isotope 153‑Ylu. Its electron configuration is predicted to be [Rn]5f^14 6d^10 7s^2, giving it a metallic appearance similar to that of gold but with a much higher density, about 20 g/cm³. The element is expected to exhibit strong relativistic effects, leading to high ionization energies and a propensity for forming ionic compounds with halogens.

Because of its extremely short half‑life, practical applications have not been demonstrated. However, stubelementein is of interest to nuclear physicists studying the limits of the periodic table and to astrophysicists modeling nucleosynthesis pathways in supernovae. Efforts to create the element in laboratories have focused on heavy ion collisions at the Large Hadron Collider and on neutron–induced fission of actinide targets.

While no experimental confirmation of stubelementein has yet been published, the search for this element continues as part of broader efforts to expand the known periodic table and to understand the behavior of superheavy nuclei.