The Fine Structure of Atoms
Electrons can orbit the nucleus only with particular properties, leading to the absorption and emission lines characteristic to each individual atom.
This model, as brilliant and clever as it is, immediately failed to produce decades old experimental results from the 19th century.
In 1887,Michelson and Morely had determined atomic emission and absorption properties of Hydrogen and they didn’t quite match the predictions of Bohr atom.
The same scientists who determined that there was no difference in the speed of light whether it moved with, against or perpendicular to the motion of the Earth, had also measured the spectral lines of Hydrogen more precisely than anyone before.
While the Bohr model came close, Michelson and Morely’s results demonstrated small shifts and extra energy states that departed slightly but significantly from Bohr’s predictions.
In particular, there were some energy levels that appeared to split into two, whereas Bohr’s model only predicted one.
Those additional energy levels, which were very close to one another and also close to Bohr’s predictions, were the first evidence of what we now call ‘The Fine Structure of Atoms’.