Stability of tetraoxides of chemical elements

Published data on the synthesis of eight-valence iridium and some other elements, and also works casting doubt on the fact of preparing iron and some 5f-elements in the oxidation state +8 were analyzed. Supposed methods (nuclear-chemical and pulse radiolysis methods) for Pu(VIII) and Am(VIII) detection and the method of matrix isolation at a temperature of 4–6 K for stabilization of eight-valence in Fe, Pu, and Am were considered.