Composition and structure of rare earth compounds at normal temperature and pressure

Sum of chemical compounds of rare earth elements represents a system, one of the main ordering factors of which is consequent disposition of compounds according to atomic numbers of REE from La to Lu. Chemical composition and strUcture of a chemical compound are attributed to ''external'' features of objects of the considered system. Sum of REE chemical compounds is presented as isostoichiometric series which are groupped in respect to the fact whether composition or structure (or both of them) are changed: 1) complete morphotropic series; 2) incomplete morphotropic series; 3) incoplete isostructural series, 4) complete isostructural series. Each of these masses is devided in five classes in respect to the anion nature: oxygenous, halide, chalcogenide, complex and intermetallic compounds. Experimental results on systematics and statistics of structural transitions in REE compounds are presented