Question

What observation led Bohr to believe that electrons had certain, finite, discrete, EXACT amounts of energies and thus were on quantized energy levels?

Answer 1

Answer: The release of light energy in packets or quanta by electrons.

Bohr discovered the following:
1. Electrons move around the nucleus in prescribed orbits.
2. When an electron jumps from an orbit with higher energy to another orbit with lower energy, the electron emits a discrete, exact amount of light energy (or a quantum of energy).
3. Boh's discovery led to the development of quantum mechanics, which defines energy release in quanta or packets, at defined frequencies and wavelengths.