Which of the following statement is/are correct?

Options

A. Contributing structures contributes to the reonance hybrid is directly proportional of their energies.
B. Equivalent contributing structures make the resonance important.
C. Contributing structures represent hypothetical molecules having no real existance.
D. Contributing structures are less stable than the resonance hybrid.

Answer

To determine which statements are correct regarding resonance and contributing structures, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A**: "Contributing structures contribute to the resonance hybrid is directly proportional to their energies."
- This statement is **incorrect**. The contribution of a resonance structure to the resonance hybrid is **inversely proportional** to its energy. Lower energy (more stable) structures contribute more to the resonance hybrid, while higher energy (less stable) structures contribute less.

2. **Statement B**: "Equivalent contributing structures make the resonance important."
- This statement is **correct**. Equivalent contributing structures (those that have similar energy and stability) enhance the resonance effect, leading to greater stability of the resonance hybrid. More equivalent structures mean a more significant resonance effect.

3. **Statement C**: "Contributing structures represent hypothetical molecules having no real existence."
- This statement is **correct**. Contributing structures are theoretical constructs used to describe the resonance phenomenon; they do not exist as isolated entities in reality. They are used to illustrate the concept of resonance and the delocalization of electrons.

4. **Statement D**: "Contributing structures are less stable than the resonance hybrid."
- This statement is **correct**. The resonance hybrid is a more stable entity than any of the individual contributing structures. The delocalization of electrons in the resonance hybrid lowers the overall energy, making it more stable compared to the contributing structures.

### Conclusion:
- The correct statements are **B, C, and D**. The only incorrect statement is **A**.