Foolium is a soft, super heavy, alkali metal. It is highly reactive, even more so than elements such as Caesium and Francium. However, it and its "relatives" (elements in the same period, but higher in number), such as Califoolium, exhibit some rather unusual reactive properties, similar to transition metals, and sometimes exist in nature in a pure form, usually after loosing their position in a salt to another element in the same period.

Foolium occasionally is found in the form of Foolium Tallides, in which it gives a single electron to a Tallium Family Element. The most common of these is Foolium Tallide (30).