Question

Which of the following statement is NOT true with Bohr's model of atom?

• A. It accounts the stability and line spectra of \( \text{He}^+ \)
• B. It fails to account for the finer details of the hydrogen atom spectrum by using sophisticated spectroscopic techniques.
• C. It is unable to explain the spectrum of atom/ion which possess only two electrons.
• D. It only explains about the splitting of spectral lines in the presence of electric field.
• E. It is unable to explain the ability of atoms to form molecules by chemical bonds.

Hint:

Bohr’s model works well only for one-electron species. It cannot explain fine structure, Stark effect, Zeeman effect, multi-electron atoms, or chemical bonding.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question asks to identify the incorrect statement about Bohr's atomic model. This requires knowing both the successes and the limitations of the model. Bohr's model was a significant step but had several shortcomings that were later addressed by quantum mechanics.
Step 2: Detailed Explanation:
Let's analyze each statement:

(A) It accounts the stability and line spectra of He\(^+\): Bohr's model is applicable to hydrogen and hydrogen-like species, which are atoms or ions with only one electron (e.g., H, He\(^+\), Li\(^{2+}\)). It successfully explained their stability and predicted their line spectra. So, this statement is true.

(B) It fails to account for the finer details of the hydrogen atom spectrum...: When the hydrogen spectrum is observed with high-resolution spectrographs, each line is found to be composed of several closely spaced lines (fine structure). Bohr's model could not explain this. So, this statement is true.

(C) It is unable to explain the spectrum of atom/ion which possess only two electrons: Bohr's model fails for any multi-electron system because it does not account for electron-electron repulsions. An atom/ion with two electrons (like He or Li\(^+\)) is a multi-electron system. So, this statement is true.

(D) It only explains about the splitting of spectral lines in the presence of electric field: The splitting of spectral lines in an electric field is called the Stark effect, and in a magnetic field, it's called the Zeeman effect. Bohr's model could not explain either of these effects. The statement says it "explains" the splitting, which is fundamentally incorrect. Therefore, this statement is NOT true.

(E) It is unable to explain the ability of atoms to form molecules by chemical bonds: Bohr's model provides no information about the shapes of molecules or the nature of chemical bonds. It treats electrons as particles in fixed orbits, which doesn't align with the concept of shared or transferred electrons in bonding. So, this statement is true.

Step 3: Final Answer:
The statement that is not true is (D), as Bohr's model fails to explain the splitting of spectral lines in electric (Stark effect) or magnetic (Zeeman effect) fields.