Which of the following electronic configuration is not possible ?

Options

A. `1s^(2)`
B. `1s^(2),2s^(2),2p^(6),3d^(10),3s^(2)`
C. `1s^(2),2s^(2),2p^(2)`
D. `1s^(2),2s^(2),2p^(6),3s^(1)`

Explanation

To determine which electronic configuration is not possible, we need to follow the order in which atomic orbitals are filled according to the Aufbau principle. The filling order is based on the increasing energy levels of the orbitals.

### Step-by-Step Solution:

1. **Understand the Aufbau Principle**: The Aufbau principle states that electrons occupy the lowest energy orbitals first before moving to higher energy orbitals. The order of filling is generally as follows:
- 1s
- 2s
- 2p
- 3s
- 3p
- 4s
- 3d
- 4p
- 5s
- 4d
- 5p
- 6s
- 4f
- 5d
- 6p
- 7s
- 5f
- 6d
- 7p

2. **Analyze the Given Options**: We need to evaluate each electronic configuration provided in the options to see if they follow the correct filling order.

3. **Evaluate Each Option**:
- **Option A**: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰
- This configuration follows the correct order of filling. Thus, it is possible.
- **Option B**: 1s² 2s² 2p⁶ 3d¹⁰ 3s² 3p⁶ 4s²
- This configuration is incorrect because the 3d orbital cannot be filled before the 3s and 3p orbitals. Therefore, this configuration is not possible.
- **Option C**: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶
- This configuration follows the correct order of filling. Thus, it is possible.
- **Option D**: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶
- This configuration also follows the correct order of filling. Thus, it is possible.

4. **Conclusion**: The only electronic configuration that is not possible is **Option B**: 1s² 2s² 2p⁶ 3d¹⁰ 3s² 3p⁶ 4s².