The implantation behaviour of isotope-separator implanted Te, Sb, and Sn in single crystals of group-IV elements (diamond, silicon, and germanium) has been studied in Mössbauer experiments on the 24-keV transition of 119Sn and in complementing channeling experiments. Radioactive 119mSn (245 d), 119mTe (4.7 d), and 119Sb (38 h) was implanted at energies of 60 keV, doses of 1013-1017 atoms/cm2, and temperatures of 20-450 °C. Large substitutional fractions are identified for all implantations. The nature and possible position of a second site observed in some implantations is discussed