JEE Chemistry 2025 Question with Solution

Given: The question asks which postulate of Bohr's model is not in agreement with the quantum mechanical model of the atom.

Find: The incorrect postulate with respect to the quantum mechanical model.

Bohr's model states that electrons can exist in stationary states, have quantized energies, and emit or absorb radiation only during transitions. These ideas remain consistent with the quantum mechanical description of discrete energy levels and transitions.

The conflicting postulate is the statement that the electron moves in a fixed circular orbit around the nucleus. In the quantum mechanical model, the electron is described by a wave function $\psi$ and occupies an orbital, which is a probability distribution, not a definite circular path.

The Heisenberg Uncertainty Principle rules out a precise classical trajectory for the electron. Therefore, the statement about circular motion is not in agreement with the quantum mechanical model.

The correct option is D.

Given: Compare Bohr's postulates with the quantum mechanical model.

Find: Which statement is inconsistent.

1. Option A says that an atom in a stationary state does not emit radiation while remaining in that state. This agrees with the idea of stationary states in quantum mechanics.

2. Option B says that only certain distinct energies $E_1, E_2, E_3$ are allowed. This agrees with quantized energy levels obtained from quantum mechanics.

3. Option C says that a photon is emitted when an electron moves from a higher energy state to a lower energy state. This also agrees with the quantum mechanical explanation of atomic spectra.

4. Option D says that the electron moves in a circle around the nucleus. This is the Bohr orbit picture, which is not accepted in quantum mechanics. Quantum mechanics replaces fixed orbits by orbitals and probability distributions.

Therefore, the postulate not in agreement with the quantum mechanical model is option D.