Nomenclature IV

Abstract

Most main group elements form only one stable ion (e. g., all members of Group 1 exist in their compounds as M ions; all members of Group 2 exist in their compounds as M ions; aluminum always exists in its compounds as an M ion). Exceptions to the “rule” that “main group elements form only one stable ion” are found among the heavier elements of groups 13, 14, and 15. For instance, thallium and indium form both +1 and +3 ions (Tl and Tl; In and In). Likewise, tin and lead form both +2 and +4 ions (Sn and Sn; Pb and Pb).