Problems of the chemical identification of new elements

The relative role of the chemical and nuclear-physical evidence for element discovery in the history of synthetic transuranium elements is analyzed. The advantages of the thermochromatography of volatile inorganic compounds for the chemical identification of transactinide elements are outlined. The physico-chemical aspects of this approach are discussed, such as the equilibrium and rates of reactions of recoil atoms, the principles of selecting the chemically active constituents of the carrier gas, the factors that determine the possibility of rapid thermochromatographic separation, and problems involved in the interpretation of the results of experiments with individual atoms. Description is given of a Monte-Carlo computer calculation technique for simulating thermochromatographic zones, which is based on a simplified realistic model of the migration of molecules along the column and permits various experimental details to be taken into account. It proves possible to separate thermochromatographically heavy actinides (up to mendelevium) in atomic state and to obtain information on the metallic states of these elements. The experiments are described aimed at the search for the spontaneously fissioning isotopes of element 107 -- ekarhenium -- in the products of the bombardment of berkelium-249 with neon-22. The technique used allows one to isolate rhenium isotopes in not more than one second. Prospects for investigating future elements including superheavy ones are discussed. (author)