Wwhich of the following statements are true about the alkali metals?

Options

A. All alkali metals form oxo salts such as carbonates, sulphates and nitrates
B. the basic character of oxides increases down the group
C. Carbonates and sulphates of lithium are stable and their stability decreases down the group
D. Solubility of carbonates and sulphates increases down the group.

Explanation

To determine which statements about alkali metals are true, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: Alkali metals form oxosalts such as carbonate, sulfate, and nitrous.**
- Alkali metals react with oxoacids to form their respective salts. For example, when alkali metals react with carbonic acid (H2CO3), sulfuric acid (H2SO4), and nitric acid (HNO3), they form carbonates, sulfates, and nitrates, respectively. Therefore, this statement is **true**.

2. **Option B: The basic character of oxides increases down the group.**
- As we move down the alkali metal group, the atomic radius increases, leading to a decrease in ionization energy. This makes it easier for these metals to lose electrons, which increases their metallic character and, consequently, the basicity of their oxides. Thus, this statement is also **true**.

3. **Option C: Carbonates and sulfates of lithium are stable, and their stability decreases down the group.**
- While lithium carbonate (Li2CO3) is indeed stable, it is less stable at high temperatures and can decompose into lithium oxide (Li2O) and carbon dioxide (CO2). However, the statement that their stability decreases down the group is misleading. While lithium's small size does lead to some unique properties, it does not mean that carbonates and sulfates of other alkali metals are necessarily more stable. Therefore, this statement is **false**.

4. **Option D: Solubility of carbonates and sulfates increases down the group.**
- The solubility of alkali metal carbonates and sulfates generally increases as we move down the group. This is due to the decrease in lattice energy, which decreases more rapidly than the hydration energy as we go down the group. Hence, this statement is **true**.

### Summary of Results:
- **Option A: True**
- **Option B: True**
- **Option C: False**
- **Option D: True**

### Final Answer:
The true statements about alkali metals are A, B, and D. Only statement C is false.

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