The
emission spectrum of a
chemical element or
chemical compound is the spectrum of
frequencies of
electromagnetic radiation emitted due to an
atom or molecule making a
transition from a high energy state to a lower energy state. The energy of the emitted
photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated
wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore,
spectroscopy can be used to identify the elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.