Which of the following exhibits inert pair effect ?

Options

A. B
B. Al
C. Tl
D. Sc

Answer

To determine which elements exhibit the inert pair effect, we need to understand what the inert pair effect is and how it relates to the electron configurations of elements.

### Step-by-Step Solution:

1. **Understanding Inert Pair Effect**:
- The inert pair effect refers to the tendency of the outermost s-electrons (the "inert pair") to remain non-bonding or unreactive in certain oxidation states, particularly in heavier elements of a group. This effect is more pronounced in the heavier p-block elements.

2. **Identifying Relevant Groups**:
- The inert pair effect is most commonly observed in the heavier elements of groups 13 (like thallium) and 14 (like lead).

3. **Electron Configuration**:
- For elements in group 13, the general electron configuration can be represented as:
- For lighter elements: ns²np¹ (e.g., Al: [Ne]3s²3p¹)
- For heavier elements: ns²np¹ (e.g., Tl: [Xe]4f¹⁴5d¹⁰6s²6p¹)
- The heavier elements (like thallium) show the inert pair effect due to the presence of filled f and d orbitals that lead to increased shielding and a reluctance of the s-electrons to participate in bonding.

4. **Examples of Elements**:
- In group 13, thallium (Tl) exhibits the inert pair effect because it has the electron configuration [Xe]4f¹⁴5d¹⁰6s²6p¹. The 6s² electrons are less likely to participate in bonding, leading to a +1 oxidation state being more stable than +3.
- Other elements in group 14, like lead (Pb), also exhibit the inert pair effect.

5. **Conclusion**:
- Therefore, the elements that exhibit the inert pair effect are primarily the heavier elements in groups 13 and 14, such as thallium (Tl) and lead (Pb).

### Final Answer:
Thallium (Tl) and Lead (Pb) exhibit the inert pair effect.