The problem of stabilisation of oxidation states and some regularities forthe periodic system of elements

The review is focused on the formulation of the basic statements of the con cept of the oxidation state stabilisation. The set of problems associated w ith the synthesis and ensuring stability of high valences for transition me tals is considered. Some new empirical data concerning the synthesis of com pounds of rare earth and d-transition metals;in unusually high oxidation st ates are analysed. The possibility of existence of + 9 and + 10 oxidation s tates for some metals (Ir, Pt, et al. in tetraoxo ions) are demonstrated. T he ways of realisation of these oxidation states are outlined. Solid compou nds or matrices with alkali-metal cations are the most suitable systems for stabilisation of these oxidation states. Some thermodynamic correlations f or metal halides and oxides are noted. Finally, a regularity in the change of the extremal oxidation states of d-transition metals is elucidated. Bibl iography - 266 references.