Question

Why does hydrogen give large number of spectral lines despite having only one electron?

Answer 1

when a hydrogen atom, having different energy levels absorbs energy the only electron can go any of the energy levels & while radiating different spectral lines observed.

Explanation:

in stationary state the only electron of hydrogen atom lies in the first energy level. when some energy absorbs by the atom the electron get promoted to higher energy levels in the excited state of the atom.now by radiating energy the atom tries to go back to its previous state.while radiating the electron can go back any one of the energy levels corresponding to different spectral lines.in a mass of hydrogen a large number of hydrogen atoms are present so for different atoms a large number of spectral lines are observed.