Why is beryllium carbonate unusually unstable thermally as compared to the other carbonates of this group?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Stability of Carbonates:**
- Carbonates are generally stable compounds. However, their thermal stability can vary significantly among different metal carbonates.

2. **Identifying Beryllium Carbonate:**
- Beryllium carbonate (BeCO₃) is known to be thermally unstable compared to other alkaline earth metal carbonates like magnesium carbonate (MgCO₃) or calcium carbonate (CaCO₃).

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