Select incorrect statement about alkaline earth metals:

Options

A. Solubility of sulphates decreases down the group
B. Solubility of hydroxides decreases down the group
C. Thermal stability of carbonates increases down the group
D. Basic nature increases down the group

Answer

To solve the question "Select the incorrect statement about alkaline earth metals," we will analyze each statement regarding the properties of alkaline earth metals, particularly focusing on their solubility, thermal stability, and basic nature.

### Step-by-Step Solution:

1. **Identify the Statements**:
- Statement 1: Solubility of sulphates decreases down the group.
- Statement 2: Solubility of hydroxides decreases down the group.
- Statement 3: Thermal stability of carbonates increases down the group.
- Statement 4: Basic nature increases down the group.

2. **Analyze Statement 1**:
- The solubility of sulphates decreases down the group.
- Explanation: As we move down the group, the size of the cation increases, which affects the hydration energy. The hydration energy decreases more significantly than the lattice energy remains constant. Thus, the solubility of sulphates indeed decreases down the group.
- Conclusion: Statement 1 is **correct**.

3. **Analyze Statement 2**:
- The solubility of hydroxides decreases down the group.
- Explanation: Hydroxides have a smaller anion (OH⁻), which means that the lattice energy is greater than the hydration energy. As we move down the group, the lattice energy decreases while the hydration energy remains relatively constant. Therefore, the solubility of hydroxides actually **increases** down the group.
- Conclusion: Statement 2 is **incorrect**.

4. **Analyze Statement 3**:
- The thermal stability of carbonates increases down the group.
- Explanation: The thermal stability of carbonates is directly related to the size of the cation. As the size of the cation increases down the group, the thermal stability of carbonates also increases.
- Conclusion: Statement 3 is **correct**.

5. **Analyze Statement 4**:
- The basic nature increases down the group.
- Explanation: The basic nature of alkaline earth metal hydroxides increases down the group due to the decrease in ionization energy and an increase in the tendency to donate a lone pair of electrons.
- Conclusion: Statement 4 is **correct**.

6. **Final Conclusion**:
- The incorrect statement about alkaline earth metals is **Statement 2: Solubility of hydroxides decreases down the group**.

### Summary:
The incorrect statement is **Statement 2**: Solubility of hydroxides decreases down the group.