If Aufbau rule is not followed, K-19 will be placed in

Options

A. s-block
B. p-block
C. d-block
D. f-block

Explanation

To solve the question of where potassium (K) with an atomic number of 19 will be placed if the Aufbau principle is not followed, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Aufbau Principle**: The Aufbau principle states that electrons fill atomic orbitals in order of increasing energy levels, typically following the n + l rule. This means that lower energy orbitals are filled before higher energy orbitals.

2. **Identify the Electron Configuration of Potassium (K)**: The atomic number of potassium is 19, which means it has 19 electrons. The normal electron configuration following the Aufbau principle would be:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

3. **Identify the Order of Filling Without Following the Aufbau Principle**: If we do not follow the Aufbau principle, we would fill the orbitals in a different order. Specifically, we would fill the 4s orbital after the 3p orbital, and then we would start filling the 3d orbital before the 4s.

4. **Fill the Orbitals**:
- Start with 1s: 1s² (2 electrons)
- Then 2s: 2s² (2 electrons)
- Then 2p: 2p⁶ (6 electrons)
- Then 3s: 3s² (2 electrons)
- Then 3p: 3p⁶ (6 electrons)
- After filling these, we would normally fill 4s¹ (1 electron) but since we are not following the Aufbau principle, we would fill 3d before 4s. So, we will fill 3d with 1 electron.

5. **Final Electron Configuration Without Following Aufbau**:
- The configuration would look like this: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s⁰.
- This means that the last electron (the 19th electron) will be in the 3d orbital instead of the 4s orbital.

6. **Conclusion**: Therefore, if the Aufbau rule is not followed, potassium (K) with atomic number 19 will have its last electron in the 3d orbital.

### Final Answer:
If the Aufbau rule is not followed, K-19 will be placed in the 3d orbital.