Question

Which is incorrect regarding Bohr model?

• A. Applicable to 1 electron system
• B. Applicable to multielectron system
• C. Electrons revolve in non-rediating orbits
• D. Angular momentum is quantised

Hint:

Remember the major failures of Bohr's model: it fails for multi-electron atoms, it violates the Heisenberg Uncertainty Principle, it cannot explain the Zeeman effect (magnetic splitting), and it cannot explain the Stark effect (electric splitting).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Niels Bohr's atomic model (1913) was a foundational step in quantum mechanics, combining classical physics with early quantum ideas to explain the emission spectrum of hydrogen. While highly successful for simple cases, it possessed fundamental limitations.
Step 2: Key Formula or Approach:
The approach involves reviewing the core postulates of Bohr's theory and its historical failures to identify the false statement among the options.
Step 3: Detailed Explanation:
Let's evaluate each statement:
- A) Applicable to 1 electron system: This is a true statement. Bohr's model perfectly predicts the spectral lines of the hydrogen atom and other hydrogen-like (single-electron) ions such as \(\text{He}^+, \text{Li}^{2+},\) and \(\text{Be}^{3+}\).
- C) Electrons revolve in non-radiating orbits: This is a true statement. It is one of Bohr's primary postulates intended to overcome the classical flaw in Rutherford's model. Bohr proposed that as long as an electron remains in a specific, allowed stationary orbit, it does not emit electromagnetic radiation.
- D) Angular momentum is quantised: This is a true statement. Another core postulate of Bohr is that an electron can only revolve in those orbits where its angular momentum (\(mvr\)) is an integral multiple of \(h/2\pi\). This quantization is what leads to discrete energy levels.
- B) Applicable to multielectron system: This is the incorrect statement. The most significant failing of Bohr's model was its inability to explain the spectra of atoms containing more than one electron (like Helium or any heavier element). The model only considers the electrostatic attraction between the nucleus and one electron; it cannot account for the complex inter-electronic repulsions present in multi-electron systems.
Step 4: Final Answer:
The claim that the Bohr model is applicable to multi-electron systems is false.