Final answer:
Bohr recognized the limitations of Rutherford's planetary model, which failed to explain certain atomic behaviors such as specific emission wavelengths and unique atomic spectra; his new theory proposed fixed electron orbits but also faced limitations, leading to the development of quantum mechanics.
Step-by-step explanation:
Niels Bohr was convinced Rutherford's planetary model of the atom had validity after working in Rutherford's laboratory. Yet, Rutherford's model could not explain why atoms emitted light at only certain wavelengths, nor could it justify the unique atomic spectra of different elements. Bohr's theory of the hydrogen atom introduced the concept of electrons orbiting at fixed energy levels, which illuminated these issues.
His model, however, raised as many questions as it answered, particularly concerning its applicability to atoms with more than one electron. Also, the idea of electrons in defined orbits conflicted with the emerging principles of quantum mechanics. It became evident that classical theories could not adequately describe atomic behavior and that a new framework was needed for the microscopic domain.