Structural parameters of close surroundings of Sr2+ and Ba2+ ions in aqueous solutions of their salts

Published data on various techniques of studying structural characteristics of close surroundings of strontium(II) and barium(II) ions in aqueous solutions of their salts under standard conditions (coordination numbers, interparticle distances, parameters of the second coordination sphere, and ionic association types) have been generalized. It has been concluded that the Sr2+ ion coordinates eight water molecules in the first coordination sphere, and the Ba2+ ion, nine water molecules, at average distances of 0.262 and 0.283 nm, respectively. Both ions form the second coordination sphere at average distances of 0.493 and 0.500 nm, respectively. There is a well-pronounced trend to the formation of ion pairs.