Flame Ionization of Silicon, Germanium and Tin

Abstract

.When compounds of Si , Ge and Sn are added to ₂/C₆H₆ diffusion flames, ions characteristic of the elements are detected in the burnt gases by mass spectrometry. The ions, which are attributed to charge exchange and proton transfer reactions of H₃O⁺, may be divided into three categories, atomic ions, protonated monoxides and protonated oxyacids . Sn gives atomic ions and protonated monoxides, a similar result to Pb , but neither Si nor Ge give atomic ions. This may be a consequence of the lack of Si and Ge atoms in the burnt gases. Ge and Sn give a protonated monoxide, but Si does not. This observation leads to the suggestion that proton affinities of the Group 4a monoxides are in the order CO, SiO < H₂O < GeO , SnO , PbO. Protonated silicic and germanic acids are observed in the burnt gases of Si - and Ge -containing flames, but no oxyacids were observed in Sn -or Pb -containing flames. This indicates that the proton affinities of both acids are greater than that of H₂O.