How can elements that have few electrons (like hydrogen)have so many sprectral lines? That is, how could hydrogen with only one atom produce so many lines.
Spectral lines are the results of electronic transitions between different energy levels. Every atom has it’s unique set of energy levels (there are a lot of them for every atom and they are discrete). Although hydrogen has only one electron, this electron (when atom is excited) can be located at any of energy levels mentioned above. This electron can transit to other energy levels (if certain conditions are followed and this transition is allowed according to transition rules), emitting or taking photons with energy |E_m-E_n | (E_m and E_n – energies of transition levels ). During experiments we observe this photons using specific devices and call them(photons) spectral lines. So elements that have few electrons (like hydrogen) have so many spectral lines because they have many energy levels and great number of possible electron transitions between them.