Why do we say atomic spectra are like finger prints of the elements?

Answer 1

Each element has a distinctive spectrum unlike that of any other element. The remainder of the analogy should be fairly clear.

Answer 2

Atomic spectra are unique for each element because they correspond to the energy levels of electrons in that element's atoms. When these electrons move between energy levels, they emit photons at specific wavelengths, creating a characteristic spectral pattern for each element. This unique pattern is analogous to a fingerprint, as it can be used to identify and differentiate elements.