If Aufbau rule is not followed, K-19 will be placed in ….. Block
(1) s (2) p (3) d (4) f

Explanation

To determine in which block K (potassium) with atomic number 19 will be placed if the Aufbau principle is not followed, we can analyze the electronic configuration of potassium.

### Step-by-Step Solution:

1. **Understanding the Atomic Number**:
- Potassium (K) has an atomic number of 19, which means it has 19 electrons.

2. **Following the Aufbau Principle**:
- According to the Aufbau principle, electrons fill the lowest energy orbitals first. The order of filling is:
- 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
- For potassium, the correct filling would be:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ (totaling 19 electrons).

3. **Not Following the Aufbau Principle**:
- If we do not follow the Aufbau principle, we would fill the electrons in a different order. We might fill them in a straight line without considering the energy levels properly.
- If we fill them in order of increasing principal quantum number (n) without considering the energy levels, we might fill them as follows:
- 1s² 2s² 2p⁶ 3s² 3p⁶, and then instead of going to 4s, we might go to 3d, leading to:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ (totaling 19 electrons).

4. **Determining the Block**:
- The blocks are determined by the subshell that is being filled:
- s-block: l = 0
- p-block: l = 1
- d-block: l = 2
- f-block: l = 3
- Since we filled an electron in the 3d subshell when not following the Aufbau principle, potassium would be placed in the **d-block**.

### Final Answer:
If the Aufbau rule is not followed, K (potassium) will be placed in the **d-block**.

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