Each element has a different atomic spectrum.
From that time to the 1920s, physicists were seeking to explain atomic spectra and blackbody radiation.
Periodic behavior of elements - elements with similar properties had similar atomic spectra.
In his work, the study of atomic and molecular spectra (called spectroscopy) plays a crucial role.
This was successful in explaining many features of atomic spectra.
The historical reason for using this quantity is that it proved to be convenient in the analysis of atomic spectra.
A fundamental application of electron configurations is in the interpretation of atomic spectra.
His rather modest hope was that the corrections introduced this way might have bearing on the problem of atomic spectra.
In seeking to explain atomic spectra an entirely new mathematical model of matter was revealed.
Early applications of pseudopotentials to atoms and solids based on attempts to fit atomic spectra achieved only limited success.