^Limitations of Bohr’s theory

1. It is valid only for single electron system.
2. Nucleus was taken as stationary but it also rotates about its own axis.
3. Couldn’t explain fine structure of spectral line.
4. Provides no information about the relative intensities of spectral lines.
5. Provides no distribution of electrons in an atom.
6. Fails to explain that why do the electrons move only in circular orbits.
7. Bohr’s theory doesn’t explain the Zeeman effect (splitting up of spectral lines in magnetic field) & Stark effect (splitting up of spectral lines in electric field).
8. Bohr’s theory doesn’t explain the doublets in the spectrum of the some atoms e.g. in sodium (5890 A⁰ & 5896 A⁰).
9. Silent about the selection rules which governs the transitions.
10. Use two theories

(i) Quantum (to explain the existence of stationary orbits) &

(ii) Classical (for motion of electrons in the orbits). These two theories essentially oppose each other.

^Spectrum of hydrogen atom

^Bohr’s frequency condition

Energy is emitted only when an electron exited to the higher states jumps back to lower states. The energy emitted is described by the relation

h f = E₁ – E₂

Ionization energy = +13.6 eV Z²

^Energy in nth orbit

Here the -ve sign of energy shows that electron is bound to the nucleus & is not free.

The binding energy of the electron in the ground state of the H-atom is called Rydberg. i.e.

1Rydberg = 13.6 eV

^Current generated