Which of the following is responsible to rule out the existence of definite paths of trajectories of electrons?

Options

A. Pauli's exclusion principle
B. Heisenberg's uncertainty principle
C. Hund's rule of maximum multiplicity
D. Aufbau principle

Answer

To determine which principle rules out the existence of definite paths or trajectories of electrons, we can analyze the given options step by step.

### Step 1: Understand the Question
The question asks which principle is responsible for ruling out the existence of definite paths of trajectories of electrons. This implies that we are looking for a principle that addresses the behavior of electrons in terms of their position and momentum.

### Step 2: Analyze the Options
1. **Pauli's Exclusion Principle**: This principle states that no two electrons can have the same set of four quantum numbers. It primarily deals with the arrangement of electrons in atoms and does not address the concept of trajectories or paths.

2. **Heisenberg's Uncertainty Principle**: This principle states that it is impossible to know both the exact position and the exact momentum (or speed) of a particle simultaneously. This uncertainty implies that electrons do not have definite paths or trajectories, as knowing one would mean losing precision on the other.

3. **Hund's Rule of Maximum Multiplicity**: This rule explains how electrons fill degenerate orbitals (orbitals of the same energy) singly before pairing up. It does not relate to the concept of trajectories.

4. **Aufbau Principle**: This principle describes the order in which electrons fill atomic orbitals, starting from the lowest energy level to higher ones. It does not address the paths or trajectories of electrons.

### Step 3: Identify the Correct Answer
From the analysis, the only principle that directly addresses the uncertainty in the position and momentum of electrons, thereby ruling out definite paths or trajectories, is **Heisenberg's Uncertainty Principle**.

### Conclusion
The correct answer to the question is **Heisenberg's Uncertainty Principle**.

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