tallium
Tallium is a hypothetical element that has been proposed but not yet discovered or synthesized. Its name and symbol (Tl) are placeholders. The concept of tallium arose from theoretical considerations within nuclear physics, particularly in relation to the stability of superheavy elements. Scientists exploring the "island of stability" — a predicted region where certain superheavy atomic nuclei are expected to be more stable than surrounding isotopes — have considered various configurations of protons and neutrons that might lead to such stability. Tallium, in this context, would represent a specific combination of atomic number and neutron number falling within or near this theoretical island. Currently, there is no experimental evidence confirming the existence of tallium. Research in this area continues, with ongoing efforts to synthesize and detect new, superheavy elements. If tallium were to be discovered, its properties would be of great interest to nuclear chemists and physicists, potentially shedding light on the fundamental forces governing atomic nuclei. The exact location on the chart of nuclides where tallium might exist remains a subject of ongoing theoretical prediction and experimental investigation.