Which of the following elements have their lower oxidation state as more stable oxidation state.

Options

A. `Sn`
B. `Pb`
C. `Tl`
D. `Bi`

Answer

To determine which of the given elements have their lower oxidation state as the more stable oxidation state, we will analyze the oxidation states of each element based on their electronic configurations and the inert pair effect.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements given in the question are Tin (Sn), Lead (Pb), Thallium (Tl), and Bismuth (Bi).

2. **Determine Electronic Configurations**:
- **Tin (Sn)**: Atomic number 50. Electronic configuration: [Kr] 5s² 4d¹⁰ 5p².
- **Lead (Pb)**: Atomic number 82. Electronic configuration: [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p².
- **Thallium (Tl)**: Atomic number 81. Electronic configuration: [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p¹.
- **Bismuth (Bi)**: Atomic number 83. Electronic configuration: [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p³.

3. **Analyze Oxidation States**:
- **Tin (Sn)**: Can exhibit +4 and +2 oxidation states. The +2 state (Sn²⁺) is more stable due to the inert pair effect, where the 5s electrons are held tightly by the nucleus.
- **Lead (Pb)**: Can exhibit +4 and +2 oxidation states. The +2 state (Pb²⁺) is more stable due to poor shielding from the 4f electrons, leading to a similar inert pair effect.
- **Thallium (Tl)**: Can exhibit +1 and +3 oxidation states. The +1 state (Tl⁺) is more stable due to the inert pair effect, where the 6s electrons are less likely to be lost.
- **Bismuth (Bi)**: Can exhibit +3 and +5 oxidation states. The +3 state (Bi³⁺) is more stable due to the same inert pair effect.

4. **Conclusion**: All four elements (Sn, Pb, Tl, and Bi) have their lower oxidation states (Sn²⁺, Pb²⁺, Tl⁺, Bi³⁺) as the more stable oxidation states.

### Final Answer:
The elements that have their lower oxidation state as the more stable oxidation state are:
- Tin (Sn)
- Lead (Pb)
- Thallium (Tl)
- Bismuth (Bi)