Which of the following pairs has less resonance energy:
`CO_(3)^(2-) " and "HCOO^(-)`

Answer

To determine which of the two species, \( \text{CO}_3^{2-} \) (carbonate ion) or \( \text{HCOO}^{-} \) (formate ion), has less resonance energy, we need to analyze their resonance structures and the stability of those structures.

### Step-by-Step Solution:

1. **Identify the Resonance Structures of \( \text{CO}_3^{2-} \)**:
- The carbonate ion has three resonance structures.
- In each structure, one of the oxygen atoms has a double bond with carbon, while the other two oxygen atoms have single bonds and carry a negative charge.
- The resonance structures can be represented as:
- Structure 1: \( O=C(O^{-})_2 \)
- Structure 2: \( O^{-}C=O(O^{-}) \)
- Structure 3: \( O^{-}O^{-}C=O \)

2. **Identify the Resonance Structures of \( \text{HCOO}^{-} \)**:
- The formate ion has two resonance structures.
- In each structure, one of the oxygen atoms has a double bond with carbon, while the other oxygen carries a negative charge.
- The resonance structures can be represented as:
- Structure 1: \( O=C(O^{-}) \)
- Structure 2: \( O^{-}C=O \)

3. **Count the Number of Resonance Structures**:
- \( \text{CO}_3^{2-} \) has 3 resonance structures.
- \( \text{HCOO}^{-} \) has 2 resonance structures.

4. **Analyze Stability of Resonance Structures**:
- In both ions, the negative charge is on the electronegative oxygen atom, which stabilizes the structures.
- However, \( \text{CO}_3^{2-} \) has more resonance structures, which generally leads to greater delocalization of charge and thus higher resonance energy.

5. **Conclusion**:
- Since \( \text{HCOO}^{-} \) has fewer resonance structures compared to \( \text{CO}_3^{2-} \), it will have less resonance energy.
- Therefore, the pair that has less resonance energy is \( \text{HCOO}^{-} \).

### Final Answer:
The pair that has less resonance energy is \( \text{HCOO}^{-} \).