Bohr model of atom is contradicted by

Options

A. Pauli’s exclusion principle
B. Planck quantum theory
C. Heisenberg uncertainty principle
D. All of these

Explanation

To answer the question "Bohr model of atom is contradicted by," we need to analyze the options provided and identify which principle or theory contradicts the Bohr model. Here’s a step-by-step solution:

### Step 1: Understand the Bohr Model
The Bohr model of the atom, proposed by Niels Bohr in 1913, describes the atom as having electrons orbiting the nucleus in fixed paths or orbits. It quantizes angular momentum and introduces the idea of energy levels.

### Step 2: Identify Key Features of the Bohr Model
- Electrons move in circular orbits around the nucleus.
- The angular momentum of the electron is quantized.
- The energy levels are discrete, meaning electrons can only occupy certain energy states.

### Step 3: Consider Contradicting Principles
To find what contradicts the Bohr model, we need to consider modern quantum mechanics principles that challenge the assumptions made by Bohr. One significant principle is the Heisenberg Uncertainty Principle.

### Step 4: Heisenberg Uncertainty Principle
The Heisenberg Uncertainty Principle states that it is impossible to simultaneously know both the exact position and exact momentum of a particle (like an electron). This principle implies that the precise orbits of electrons, as suggested by the Bohr model, cannot exist because knowing one quantity with certainty would lead to complete uncertainty in the other.

### Step 5: Conclusion
Based on the above analysis, the Bohr model of the atom is contradicted by the Heisenberg Uncertainty Principle.

### Final Answer
The Bohr model of the atom is contradicted by the Heisenberg Uncertainty Principle.

---