Question

Bohr's model can explain:
1. the spectrum of hydrogen atom only
2. spectrum of atom or ion containing one electron only
3. the spectrum of hydrogen molecule
4. the solar spectrum

Answer 1

Correct Answer - Option 2 : spectrum of atom or ion containing one electron only

Concept:

• Bohr’s Model: Niel's Bohr by making 4 postulates solved the puzzle of hydrogen spectra.

       1.The electrons revolve around the nucleus in circular orbits.

       2.The radius around the orbit has some special values of the radius. In these stationary orbits, they do not radiate energy as expected from Maxwell’s laws.

       3.The energy of each stationary orbit is fixed, electrons can jump from a higher orbit to a lower orbit by emitting a photon of radiation.

(Higher energy orbit – Lower energy orbit) = (h c)/λ  

• An electron can also jump from lower to higher energy by absorbing energy.

      4.In stationary orbits, the angular momentum L of an electron is an integral multiple of (h/2π).

L = n × (h/2π)

• Limitations of Bohr’s Model:
  • It could not work for atoms and ions having more than one electron not even for Helium.

Explanation:

• The Bohr model failed as the model could not explain the spectra of atoms or ions having two or more electrons.

• Because the Bohrs model is valid to an atom or ion having only one electron such as H, He⁺, Li⁺⁺, Be⁺⁺⁺, etc...

Bohr's model can explain the spectrum of atoms or ions containing one electron only.