Which of the following is not according to the Pauli exclusion principle?

Options

A.
B.
C.
D. A and B both

Answer

To solve the question regarding which of the given configurations is not according to the Pauli exclusion principle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Pauli Exclusion Principle**:
- The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. This means that in any given atomic orbital, a maximum of two electrons can occupy the same orbital, and they must have opposite spins.

2. **Identify the Quantum Numbers**:
- The four quantum numbers are:
1. Principal quantum number (n)
2. Azimuthal quantum number (l)
3. Magnetic quantum number (m_l)
4. Spin quantum number (m_s)

3. **Analyze Each Configuration**:
- We need to evaluate the provided configurations to check if they adhere to the Pauli exclusion principle.
- **Configuration 1**: Check if both electrons have the same spin. If they do, this configuration violates the principle.
- **Configuration 2**: Similarly, check if there are more than two electrons in a single orbital or if they have the same spin.
- **Configuration 3**: Ensure that the electrons are filled according to the principle, with opposite spins for any two electrons in the same orbital.

4. **Determine Which Configuration Violates the Principle**:
- After analyzing the configurations:
- If Configuration 1 has two electrons with the same spin, it violates the principle.
- If Configuration 2 has more than two electrons in a single orbital or electrons with the same spin, it also violates the principle.
- Configuration 3 should follow the principle if it has two electrons with opposite spins.

5. **Conclusion**:
- Identify which configurations do not adhere to the Pauli exclusion principle. Based on the analysis, if both Configuration 1 and Configuration 2 violate the principle, then the answer would be that both of these configurations are not according to the Pauli exclusion principle.

### Final Answer:
- The configurations that are not according to the Pauli exclusion principle are Configuration 1 and Configuration 2.