Question

Which of the following is correct in the case of the Bohr model of atoms?
A. Predicts continuous emission spectra for all atoms
B. Assumes that the angular momentum of electrons is quantised
C. Predicts same emission spectrum for singly ionised neon atom and hydrogen atom
D. Predicts same emission spectrum for singly ionised neon atom and singly ionised helium atom

• A. C
• B. B
• C. A
• D. D

Hint:

Bohr model works only for hydrogen-like species and introduces quantisation of angular momentum as its fundamental assumption.

Answer 1

The Correct Option is B

Step 1: Recall Bohr model postulates.
Bohr model states that electrons revolve in fixed circular orbits without radiating energy and only certain discrete orbits are allowed.

Step 2: Angular momentum quantisation.
One of the key postulates is that angular momentum is quantised:
\[ mvr = \frac{nh}{2\pi} \]
Thus, statement (B) is correct.

Step 3: Analyze statement (A).
Bohr model predicts discrete line spectra, not continuous spectra.
Hence, (A) is incorrect.

Step 4: Analyze statement (C).
Singly ionised neon is not a hydrogen-like species, so it will not have the same spectrum as hydrogen.
Thus, (C) is incorrect.

Step 5: Analyze statement (D).
Singly ionised helium (\( He^+ \)) is hydrogen-like, but neon ion is not.
Hence, their spectra are different.

Step 6: Conclusion.
Only statement (B) is correct.
\[ \boxed{B} \]