Intert pair effect is observed in elements of which block:

Options

A. `s`
B. `p`
C. `d`
D. `f`

Answer

To solve the question regarding which block of the periodic table exhibits the inert pair effect, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Inert Pair Effect**:
- The inert pair effect refers to the tendency of the s-electrons (the two electrons in the outermost s orbital) to remain non-bonding or inert in heavier elements. This means that these s-electrons do not participate in bonding as effectively as they do in lighter elements.

2. **Identify the Blocks of the Periodic Table**:
- The periodic table is divided into four main blocks:
- S block (Groups 1 and 2)
- P block (Groups 13 to 18)
- D block (Transition metals)
- F block (Lanthanides and Actinides)

3. **Determine Which Block Exhibits the Inert Pair Effect**:
- The inert pair effect is predominantly observed in the heavier elements of the P block. This is because, as we move down the group in the periodic table, the s electrons become less involved in bonding due to increased shielding and the effective nuclear charge experienced by the outer electrons.

4. **Conclusion**:
- Therefore, the inert pair effect is observed in elements of the P block.

### Final Answer:
The inert pair effect is observed in elements of the **P block**.

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