Answer
a. Explains spectra of atoms with a single valence electron, predicts hydrogen ionization energy, explains hydrogen stability.
b. Spectra for atoms that are unlike hydrogen, intensity of closely-spaced spectral lines.
Work Step by Step
a. Successes: explains why atoms emit line spectra, explains absorption spectra, predicts the spectrum of emitted light for hydrogen, predicts the ionization energy of hydrogen, explains why atoms are stable.
b. Observations it could not explain: spectra for atoms other than hydrogen, varying intensities of emission lines, and the “fine structure” of closely-spaced spectral lines.
