1. The problem statement, all variables and given/known data "A gas discharge tube contains H 1 , H2, He 3 , He4, Li6, and Li7 ions and atoms (the superscript is the atomic mass), with the last four ionized so as to have only one electron. (a) As the potential across the tube is raised from zero, which spectral line should appear first? (b) Give, in order of increasing frequency, the origin of the lines corresponding to the first line of the Lyman series of H 1 ." 2. Relevant equations 3. The attempt at a solution I have no problem with part (a), but I don't quite get what they're asking for in part (b).