Which of the following postulate of Bohr's model of hydrogen atom is not in agreement with quantum mechanical model of an atom?
- The electron in a H atom's stationary state moves in a circle around the nucleus.
- 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.
- An atom in a stationary state does not emit electromagnetic radiation as long as it stays in the same state.
- 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.
Answer
(1) The electron in a H atom's stationary state moves in a circle around the nucleus.
Solution
As per NCERT, the Heisenberg uncertainty principle rules out a definite path (orbit) for an electron: its position and momentum cannot both be known exactly.
In the quantum mechanical model the electron is described by an orbital (a region of probability 2), not by a circular orbit.
Postulate (1) does not agree with the quantum mechanical model.
Quantised energy levels (2), no radiation while in a stationary state (3) and emission of a photon of energy E = h during a downward transition (4) are all retained in the quantum mechanical model.
Answer: (1)