Assertion (A) The carbonate of lithium decomposes easily on heating to form lithium oxide and `CO_(2)`.
Reason (R) Lithium being very small in size polarises large carbonate ion leading to the formation of more stable `Li_(2)O` and `CO_(2)`.

Options

A. Both A and R are correct and R is the correct explanation of A
B. Both A and R are correct but R is not the correct explanation of A
C. Both A and R are not correct
D. A is not correct but R is correct

Explanation

To solve the assertion and reason question regarding lithium carbonate, we will break down the solution step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "the carbonate of lithium decomposes easily on heating to form lithium oxide and carbon dioxide."
- This is a statement about the behavior of lithium carbonate (Li2CO3) when subjected to heat.

2. **Stability of Carbonates**:
- It is known that the stability of carbonates decreases as we move down the group in the periodic table.
- Lithium, being at the top of Group 1 (alkali metals), has the least stable carbonate compared to other alkali metal carbonates.

3. **Decomposition Reaction**:
- Since lithium carbonate is the least stable, it readily decomposes upon heating.
- The decomposition reaction can be represented as:
\[ \text{Li}_2\text{CO}_3 \rightarrow \text{Li}_2\text{O} + \text{CO}_2 \]
- This confirms that the assertion is correct.

4. **Understanding the Reason**:
- The reason states that "lithium being very small in size polarizes the large carbonate ion leading to the formation of more stable Li2O and CO2."
- Lithium ions (Li⁺) are indeed small in size compared to the carbonate ion (CO3²⁻).

5. **Polarization Effect**:
- The small size of Li⁺ gives it a high polarizing power, which means it can distort the electron cloud of the carbonate ion.
- This polarization weakens the bonds within the carbonate ion, making it more susceptible to decomposition.

6. **Conclusion**:
- Since lithium carbonate is easily polarized due to the small size of lithium ions, it leads to the breakdown of Li2CO3 into more stable products (Li2O and CO2).
- Therefore, both the assertion and reason are correct, and the reason correctly explains the assertion.

### Final Conclusion:
Both the assertion (A) and reason (R) are correct, and the reason is the correct explanation for the assertion.

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