Which of the following is most stable ?

Options

A. `BeCO_3`
B. `MgCO_3`
C. `SrCO_3`
D. `CaCO_3 `

Answer

To determine which carbonate is the most stable among the group 2 carbonates, we can follow these steps:

### Step 1: Identify the Group 2 Carbonates
Group 2 carbonates include those of Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). We will focus on the stability of these carbonates.

### Step 2: Understand Stability Trends
The stability of carbonates increases as we move down the group from Beryllium to Barium. This is due to the decreasing polarizing power of the M²⁺ ions as their size increases.

### Step 3: Analyze Polarizing Power
- **Beryllium (Be²⁺)** has a small ionic radius and a high charge density, making it highly polarizing. This leads to a significant distortion of the carbonate ion (CO₃²⁻), resulting in the decomposition of BeCO₃ into BeO and CO₂.
- **Magnesium (Mg²⁺)**, while still polarizing, has a larger ionic radius than Be²⁺, leading to slightly less distortion of the carbonate ion.
- **Calcium (Ca²⁺)**, **Strontium (Sr²⁺)**, and **Barium (Ba²⁺)** continue this trend, with their polarizing powers decreasing further due to their increasing ionic sizes.

### Step 4: Conclusion on Stability
As we move down the group, the stability of the carbonates increases due to the reduced polarizing power of the cations. Therefore, Strontium carbonate (SrCO₃) is the most stable among the group 2 carbonates discussed, as it is located lower in the group compared to Beryllium, Magnesium, and Calcium.

### Final Answer
The most stable carbonate among the group 2 carbonates is **Strontium Carbonate (SrCO₃)**.

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