# Can scientists tell the energy levels of the atom?

In the hydrogen spectral series how did the scientists know the number of the energy level which the electron is moving from or to?

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The first series of Hydrogen lines to be discovered was the Balmer Series, and nobody knew why they were discrete lines instead of a continuous spectrum. Johann Balmer discovered that the lines all had wavelengths equal to, $$\lambda_n = \left({n^2 \over n^2-4}\right)\times 364.5068\;\text{nm.}$$
Later on, it was realized that there were other lines with $m^2$ instead of 4 in the denominator. Later still, the Bohr model of the atom was able to reproduce this pattern of energy levels. Improvements to this came with Quantum Mechanics and various corrections.