The thermal stability of alkaline earth metal carbonates increases from Be to Ba. This is because

Options

A. Covalent nature decreases and lonic nature increases
B. Lattice energy increases
C. Electropositive nature decreases
D. None of these

Answer

To solve the question regarding the thermal stability of alkaline earth metal carbonates increasing from beryllium (Be) to barium (Ba), we can follow these steps:

### Step 1: Understanding Thermal Stability
Thermal stability refers to the ability of a compound to withstand heat without decomposing. In the case of alkaline earth metal carbonates, this stability can be influenced by the nature of the bonding within the compound.

**Hint:** Remember that thermal stability is related to how much heat a compound can tolerate before breaking down.

### Step 2: Analyzing the Alkaline Earth Metals
The alkaline earth metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). As we move down the group in the periodic table, the size of the metal cations increases.

**Hint:** Consider how the size of the cation affects the type of bonding in the carbonates.

### Step 3: Covalent vs. Ionic Character
According to Fajans' rules, a smaller cation with a larger anion tends to form more covalent character in the bond. Conversely, as the size of the cation increases (moving down the group), the covalent character decreases, and the ionic character increases.

**Hint:** Think about how the size of the cation influences the nature of the bond (ionic vs. covalent).

### Step 4: Impact of Ionic Character on Thermal Stability
Ionic compounds generally have higher melting and boiling points compared to covalent compounds. Therefore, as the ionic character of the alkaline earth metal carbonates increases from Be to Ba, their thermal stability also increases.

**Hint:** Recall that higher ionic character typically means higher thermal stability due to stronger ionic bonds.

### Step 5: Conclusion
Based on the analysis, we can conclude that the thermal stability of alkaline earth metal carbonates increases from Be to Ba because the covalent character decreases and the ionic character increases.

**Final Answer:** The correct option is that the covalent nature decreases and ionic nature increases.

### Summary of Steps:
1. Understand thermal stability.
2. Analyze the alkaline earth metals.
3. Compare covalent and ionic character.
4. Relate ionic character to thermal stability.
5. Conclude with the correct answer.