Work Step by Step
The single electron in hydrogen can be excited up to a higher energy level from its ground state. There are many such energy levels to choose from. The spacing between these levels varies, which means there are many different ways for the electron to return to its ground level as it hops down into lower levels. Each different transition emits a photon of a different frequency, leading to a spectrum of many spectral lines, even for hydrogen, which has just one electron.