Question

Bohr's model could explain the spectra:

• A. of electron species having one electron.
• B. in the presence of magnetic field.
• C. in the presence of electric field.
• D. of metal atoms.

Answer 1

Answer: (A)

Limitations of Bohr's Model :

Bohr’s theory was unable to explain the following observations :

i) Bohr’s model could not explain the spectra of atoms containing more than one electron.

ii) It could not explain the Zeeman effect.

In presence of the magnetic field, each spectral line gets split up into fine lines, the phenomenon is known as Zeeman effect.

iii) It could not explain the Stark effect.

In presence of the electric field, each spectral line gets split up into fine lines, the phenomenon is known as the Stark effect.

iv) The main objection to Bohr’s model was raised by Heisenberg’s uncertainty principle.

According to Heisenberg’s uncertainty principle, it is impossible to determine simultaneously the exact position and the momentum of a small moving particle like an electron.

But, according to Bohr’s model electron moves in well-defined orbits around the nucleus, and hence its position, as well as momentum, can be determined simultaneously, which is against the uncertainty principle.

So, electron moves in well-defined orbits around the nucleus is impossible.

Hence, the correct option is $\text{A}$