Thalorium

Thalorium is a theoretical chemical element that has not yet been observed experimentally. It is proposed to occupy the 7th period of the periodic table, following the known elements of the actinide series. In some hypothesized models its atomic number is 107, with the symbol Tl′. The element would be placed directly above lawrencium and would belong to the group of transuranium elements.

Predicted properties of thalorium come from extrapolations of relativistic density‑functional calculations. It is expected to be a heavy, radioactive metal, with a density exceeding that of mercury. Its electronic configuration would end with a 7p block, suggesting possible oxidation states of +4 and +6. The first isotope might exhibit a half‑life on the order of minutes to hours, depending on nuclear stability arguments. Due to its heavy mass, thalorium would likely have significant relativistic effects affecting its chemical behaviour, potentially making it more covalent than typical actinides.

Because no isotope of thalorium has been synthesized, its chemistry remains purely speculative. Theoretical studies propose that it could form oxides or halides that would be soluble in polar solvents, and its complexes might show unusual spectroscopic signatures due to f‑electron involvement. Predicted applications are limited to fundamental research in nuclear physics and high‑energy material science, rather than any commercial use.

Research into thalorium is ongoing within high‑energy physics laboratories that routinely collide ions at relativistic speeds. Experimental attempts aim to produce it via multi‑step fusion reactions involving heavy target nuclei and intense ion beams. If successful, the first observed decay products could confirm its existence and open new avenues for studying the limits of nuclear stability. The element remains hypothetical, and any discovery would prompt a revision of current models of the actinide column and the periodic table beyond the known transuranium series.