The important principals that do not help in assigning electronic configguration to atoms are

Options

A. Aufbau rule
B. Hund's rule
C. Heisenberg's uncertainity principle
D. Pauil's exciasion principle

Answer

To determine which principles do not help in assigning electronic configurations to atoms, we need to analyze the four key principles involved in the process:

1. **Aufbau Principle**: This principle states that electrons fill atomic orbitals starting from the lowest energy level to the highest. It is crucial for determining the order in which electrons occupy orbitals.

2. **Hund's Rule**: This rule states that electrons will fill degenerate orbitals (orbitals of the same energy) singly before pairing up. This helps in maximizing the total spin and is important for understanding the distribution of electrons in orbitals.

3. **Pauli Exclusion Principle**: This principle states that no two electrons in an atom can have the same set of four quantum numbers. This is essential for ensuring that each electron is uniquely identified in its orbital.

4. **Heisenberg Uncertainty Principle**: This principle states that it is impossible to simultaneously know both the position and momentum of an electron with absolute precision. While this principle is fundamental to quantum mechanics, it does not directly aid in the assignment of electronic configurations.

### Step-by-Step Solution:

1. **Identify the Principles**: List the four principles relevant to electronic configuration: Aufbau Principle, Hund's Rule, Pauli Exclusion Principle, and Heisenberg Uncertainty Principle.

2. **Analyze Each Principle**:
- **Aufbau Principle**: Important for assigning electronic configuration as it dictates the order of filling.
- **Hund's Rule**: Important for determining how electrons fill degenerate orbitals.
- **Pauli Exclusion Principle**: Important for ensuring that no two electrons have the same quantum numbers.
- **Heisenberg Uncertainty Principle**: Not useful for assigning electronic configurations as it deals with the limitations of measuring position and momentum.

3. **Conclusion**: The principle that does not help in assigning electronic configurations is the **Heisenberg Uncertainty Principle**.

### Final Answer:
The important principle that does not help in assigning electronic configuration to atoms is the **Heisenberg Uncertainty Principle**.