The hydrogen atom problem was one that was very perplexing to the pioneers of quantum theory. While its quantized nature was evident from the known atomic emission spectra, there were no models that could adequately describe the patterns seen in the spectra. 6.1: Older Models of the Hydrogen Atom Two of the most important (historically) models of the hydrogen atom and it’s energy levels/spectra were proved by Johannes Balmer, a high school teacher, and Niels Bohr, a Danish physicist. 6.2: The Quantum Mechanical H-atom As is so often the case for quantum mechanical systems, the story of the hydrogen atom begins with writing down the Hamiltonian describing the system. 6.3: Rydberg Spectra of Polyelectronic Atoms To a very good approximation, the electronic spectra of highly excited atoms look a lot like the spectrum of hydrogen. 6.4: References 6.5: Vocabulary and Concepts 6.6: Problems Thumbnail: Hydrogen atom. (Public Domain; Bensaccount via Wikipedia )