Select INCORRECT about inert pair effect.

Options

A. It is observed effectively in lighter post transition elements
B. Lower oxidation state is due to loss of electrons from ns orbital and retention of np electrons
C. In the chloride of p-block metals conversion of`MX_(n)rarrMX_(n-2)+X_(2)`
D. Ga(III) compound obtain by difficulty but TI(III) can be obtained easily

Answer

To solve the question regarding the incorrect statements about the inert pair effect, we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Understanding the Inert Pair Effect**:
The inert pair effect refers to the tendency of the outermost s-electrons (ns) in heavier p-block elements to remain non-bonding or inert during chemical reactions. This results in the stability of lower oxidation states.

2. **Analyzing Statement 1**:
- **Statement**: "It is observed effectively in lighter post-transition elements."
- **Analysis**: The inert pair effect is primarily observed in heavier p-block elements, not lighter ones. Therefore, this statement is **incorrect**.

3. **Analyzing Statement 2**:
- **Statement**: "Lower oxidation state is due to loss of electron from Ns orbital and retention of Np electrons."
- **Analysis**: The lower oxidation state results from the retention of ns electrons (not loss) while the np electrons participate in bonding. This statement is also **incorrect**.

4. **Analyzing Statement 3**:
- **Statement**: "In chloride of p-block metals, conversion of MxN giving MxN-2 plus X2."
- **Analysis**: This statement is correct as it describes a reaction where a higher oxidation state compound (like PbCl4) can convert to a lower oxidation state compound (like PbCl2) due to the inert pair effect.

5. **Analyzing Statement 4 (D)**:
- **Statement**: "Gallium plus 3 compound obtained by difficulty but Tl plus 3 compound can be obtained easily."
- **Analysis**: This statement is misleading. While it is true that thallium can stabilize a +3 oxidation state, gallium typically does not form a stable +1 state as readily as thallium. Thus, this statement is also **incorrect**.

### Conclusion:
Based on the analysis, the incorrect statements about the inert pair effect are:
- Statement 1 (incorrect)
- Statement 2 (incorrect)
- Statement 4 (D) (incorrect)
- Statement 3 is the only correct statement.

### Final Answer:
The incorrect statements about the inert pair effect are A, B, and D.

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