Effective radii of the monovalent coin metals

Abstract

Nearly all text books, tabulations, periodic systems and data banks give a rather large effective radius for Au + , typically 137 pm, corresponding to the order R(Cu + )<R(Ag + )<R(Au + ). In contrast, experimental and theoretical data unanimously corroborate a completely different smaller value, caused by 16 pm lanthanoid contraction and 13 pm relativistic contraction, although the outer occupied 5d shell is relativistically expanded. In addition, small changes of the surrounding crystal structure may modify the effective radii by several pm. For coordination number CN=2, R(Au + ) is about 60 pm, i.e. definitely smaller than R(Ag + )≃70 pm [reference R(O 2- )=138 pm]