The thermal stability order of the carbonates is

Options

A. `Na_(2)CO_(3)gt K_(2)CO_(3)gtBeCO_(3)gt BaCO_(3)`
B. `K_(2)CO_(3)gt Na_(2)CO_(3) gt BaCO_(3) gt BeCO_(3)`
C. `BaCO_(3)gtBeCO_(3)gtK_(2)CO_(3)gtNa_(2)CO_(3)`
D. `BeCO_(3)gt Na_(2)CO_(3)gt BaCO_(3) gt K_(2)CO_(3)`

Answer

To determine the thermal stability order of carbonates, we need to consider the factors that influence the stability of these compounds. The stability of carbonates can be influenced by the size and charge of the cation associated with the carbonate ion (CO3^2-).

### Step-by-Step Solution:

1. **Understanding Carbonate Stability**:
- The thermal stability of carbonates is influenced by the cation's size and charge. Larger cations can stabilize the larger carbonate ion better than smaller cations.

2. **Cation Size**:
- As the size of the cation increases, the thermal stability of the carbonate also increases. This is because larger cations can better accommodate the larger carbonate ion, leading to greater stability.

3. **Cation Charge**:
- The charge of the cation also plays a crucial role. Cations with a lower charge tend to stabilize the carbonate ion better than those with a higher charge. Higher charged cations can lead to increased polarizability, which destabilizes the carbonate.

4. **Order of Stability**:
- Based on the above factors, we can establish a general order of thermal stability for the carbonates of the alkali and alkaline earth metals:
- **Beryllium Carbonate (BeCO3)**: Least stable due to small size and high charge.
- **Magnesium Carbonate (MgCO3)**: More stable than BeCO3 but less stable than larger cations.
- **Calcium Carbonate (CaCO3)**: More stable than MgCO3.
- **Strontium Carbonate (SrCO3)**: More stable than CaCO3.
- **Barium Carbonate (BaCO3)**: Most stable due to the largest cation size and lowest charge.

5. **Final Order**:
- The thermal stability order of carbonates can be summarized as:
- **BaCO3 > SrCO3 > CaCO3 > MgCO3 > BeCO3**

6. **Identifying the Correct Option**:
- From the options provided, we need to identify which one correctly reflects this order. The correct option will indicate that beryllium carbonate is the least stable.