Limitations of Bohr's Atomic Model

Bohr's model was highly successful for the Hydrogen atom (which has only 1 electron) or single-electron ions like He+ and Li2+. However, it completely failed to explain the complex atomic spectrum of heavier atoms that contain multiple electrons.

• Zeeman Effect: When an atom is placed in a strong magnetic field, its spectral lines physically split into multiple finer lines. Bohr's model could not explain this.
• Stark Effect: Similarly, the splitting of spectral lines under a strong electrical field could not be accounted for by Bohr's equations.

Bohr assumed that electrons revolve in perfectly defined, fixed circular orbits with exact velocities and exact positions. However, Heisenberg's Uncertainty Principle proved that it is physically impossible to know both the exact position and momentum of a microscopic electron simultaneously.

Bohr treated the electron purely as a solid particle. He completely ignored the dual nature of matter (de Broglie's hypothesis), failing to account for the wave-like properties of moving electrons.