superactinoid

The term "superactinoid" refers to a hypothetical series of elements in the periodic table that would follow the actinoids. This series, starting around element 122, would involve the filling of inner electron shells, specifically the 5g and 6f orbitals, similar to how the lanthanoid and actinoid series are formed.1

This series is predicted to contain 32 elements, potentially extending up to element 153. However, predicting the exact chemical properties of these superactinoids is complex. This is due to uncertainties about when the 5g and 6f orbitals begin to fill, and the close energy levels of these orbitals with the 8p and 7d orbitals. This overlap could lead to a commingling of orbital filling, resulting in elements with multiple, difficult-to-distinguish oxidation states. The orderly extrapolation of properties seen in lighter elements may not hold true for this region of the periodic table.1