[en] One could set up magnetochemical series for ligands as well as central ions in alkali metal lanthanide oxides or halides. In order to explain the magnetic behaviour of these compounds, the angular overlap model (AO) was used amongst others. The AO parameter esub(sigma)(R) could be clearly determined for a few compound series (from susceptibility measurements). Taking the (calculated) overlap integral S²sub(sigma)(R) into consideration and additional relationships, the magnetochemical series of the ligands were obtained I^- < Br^- < Cl^- < F^- approx. O^2- as well as of the lanthanides. The course of the latter series corresponds to the lanthanide contraction. (orig.)