Which of the following anions is most easily polarized ?

Options

A. `CI^(-)`
B. `Se^(2-)`
C. `Br^(-)`
D. `Te^(2-)`.

Answer

To determine which of the given anions is most easily polarized, we will analyze the polarizability of each anion based on their size and charge. The anions provided are Cl⁻ (chloride), Br⁻ (bromide), Se²⁻ (selenide), and Te²⁻ (telluride).

### Step-by-Step Solution:

1. **Understand Polarizability**:
- Polarizability refers to the ability of an anion to become distorted in its electron cloud due to the presence of a nearby positive charge. Greater polarizability indicates that the anion can be more easily distorted.

2. **Factors Affecting Polarizability**:
- The polarizability of an anion increases with its size. Larger anions have more electrons that can be distorted.
- The charge on the anion also affects polarizability; anions with higher negative charges tend to be larger and thus more polarizable.

3. **Analyze the Given Anions**:
- **Cl⁻ (Chloride)**: This anion has a single negative charge and is relatively small in size.
- **Br⁻ (Bromide)**: This anion also has a single negative charge but is larger than Cl⁻.
- **Se²⁻ (Selenide)**: This anion has a double negative charge and is larger than both Cl⁻ and Br⁻.
- **Te²⁻ (Telluride)**: This anion also has a double negative charge and is larger than Se²⁻ due to having more electron shells.

4. **Comparison of Sizes**:
- Among the anions, the order of size is as follows: Te²⁻ > Se²⁻ > Br⁻ > Cl⁻.
- Since Te²⁻ has the largest size, it will have the highest polarizability.

5. **Conclusion**:
- Based on the analysis, Te²⁻ (telluride) is the most easily polarized anion among the options provided.

### Final Answer:
The anion that is most easily polarized is **Te²⁻ (Telluride)**.