Umbrium
Umbrium is a hypothetical element with the symbol Um and atomic number 137. It is not a naturally occurring element and has not been synthesized or observed. Its properties are largely theoretical and are extrapolated from trends in the periodic table, particularly concerning superheavy elements.
The theoretical placement of Umbrium in the periodic table suggests it would reside in the g-block, a
The existence of elements with atomic numbers beyond the current experimentally confirmed range, such as Umbrium,