Ununi

Ununi, also known as element 121, is a hypothetical chemical element with the symbol Uun and atomic number 121. It would belong to the superactinide series and the g-block of the periodic table. As of current scientific understanding, ununi has not been synthesized or detected. Its existence is predicted by theoretical models of atomic structure, which suggest that elements beyond those currently known may exist within an "island of stability" where they could have longer half-lives.

The properties of ununi are largely speculative. Theoretical calculations suggest it would be a metal and its electron configuration would place it as the first element in the g-block. However, the relativistic effects that become significant for such heavy elements make precise predictions of its chemical behavior challenging. If synthesized, ununi would likely be highly radioactive, with a very short half-life, making it difficult to study. The ongoing quest to synthesize superheavy elements, including ununi, is a significant area of research in nuclear physics and chemistry, aiming to test the limits of nuclear stability and explore the fundamental principles governing atomic structure.