In a given atom no two electrons can have the same values for all the four quantum numbers. This is called

Options

A. Hund's rule
B. Aufbau's principle
C. Uncertainty principle
D. pauli's exclusion principle

Answer

To solve the question "In a given atom no two electrons can have the same values for all the four quantum numbers. This is called," we need to identify the principle that describes this phenomenon.

### Step-by-Step Solution:

1. **Understanding Quantum Numbers**:
- Each electron in an atom is described by four quantum numbers:
- Principal quantum number (n): Indicates the energy level.
- Azimuthal quantum number (l): Indicates the shape of the orbital.
- Magnetic quantum number (m_l): Indicates the orientation of the orbital.
- Spin quantum number (m_s): Indicates the spin direction of the electron (either +1/2 or -1/2).

2. **Identifying the Principle**:
- The question states that no two electrons can have the same set of all four quantum numbers. This means that if one electron is described by a specific set of quantum numbers, another electron in the same atom cannot share that exact set.

3. **Recalling Relevant Principles**:
- The principle that states this is known as **Pauli’s Exclusion Principle**. It asserts that in an atom, no two electrons can occupy the same quantum state simultaneously.

4. **Conclusion**:
- Therefore, the answer to the question is: **Pauli's Exclusion Principle**.