Given below are two statements:
Statement I : According to Bohr's model of hydrogen atom, the angular momentum of an electron in a given stationary state is quantised.
Statement II : The concept of electron in Bohr's orbit, violates the Heisenberg uncertainty principle.
In the light of the above statements, choose the most appropriate answer from the options given below:

Solution

Chemistry ma’am · 3 steps

Bohr fixed both the orbit radius and the electron's speed, and Heisenberg says you cannot know both together.

1. Statement I. Bohr's postulate says an electron can only move in orbits where its angular momentum is a whole-number multiple of h/2π. So the angular momentum is quantised, and Statement I is correct.

   mvr = nh/2π, n = 1, 2, 3, …

2. Statement II. A Bohr orbit has a fixed radius, so the electron's position is known exactly. Its speed in that orbit is also fixed, so its momentum is known exactly. The uncertainty principle, Δ x · Δ p ≥ h/4π, forbids knowing both at once, so Statement II is correct.
3. So. Both statements are correct, which is option (c). This conflict with Heisenberg is one of the reasons the Bohr model was replaced by the quantum mechanical model.

The idea to keep. Bohr gives the electron a definite path: a fixed radius and a fixed speed together. Any picture that pins down both position and momentum breaks the uncertainty principle.

Answer from the NTA final answer key. Solution by PrepWiser.