Q. Which of the following postulate of Bohr's model of hydrogen atom
is not in agreement with quantum mechanical model of an atom?
A. The electron in a H atom's stationary state moves in a circle around the nucleus.
B. An atom can take only certain distinct energies E1, E2, E3, etc.
These allowed states of constant energy are called the stationary states of atom.
C. An atom in a stationary state does not emit electromagnetic radiation
as long as it stays in the same state.
D. When an electron makes a transition from a higher energy stationary state
to a lower energy stationary state, then it emits a photon of light.
Explanation
Step 1: Analyze statement A
Bohr assumed that electron moves in a definite circular orbit.
Quantum mechanical model does not support fixed circular paths
for electrons.
Step 2: Analyze statements B, C and D
Quantization of energy levels, existence of stationary states and
emission/absorption of radiation during transitions are consistent
with quantum mechanics.
Correct Answer = A