Three resonance structures are shown for nitrous oxide (N2O). Which structure is the lowest energy? In other words, which structure represents the real molecule?
The top structure is the lowest energy
The center structure is the lowest energy
The bottom structure is the lowest energy
The real molecule is an average of all three structures because all three are equivalent (i.e. have the same energy)
The Correct Answer and Explanation is :
The lowest-energy resonance structure for nitrous oxide (N₂O) is the top structure shown in the provided image.
Explanation:
To determine which resonance structure is the most stable, we analyze the formal charges and bonding in each structure. The general rules for evaluating resonance structures are:
- Minimize formal charges: The most stable structure has the least separation of charge.
- Follow the octet rule: Each atom should have a complete octet whenever possible.
- Negative formal charges should be on the more electronegative atom: Oxygen is more electronegative than nitrogen, so it should carry any negative charge.
- Avoid placing positive charges on highly electronegative atoms.
Formal Charge Calculation:
The formal charge (FC) of an atom is calculated using the formula:
[
\text{FC} = \text{valence electrons} – \text{nonbonding electrons} – \frac{\text{bonding electrons}}{2}
]
For the top structure:
- The leftmost nitrogen (N) has a formal charge of +1.
- The central nitrogen (N) has a formal charge of 0.
- The oxygen (O) has a formal charge of -1.
This satisfies stability conditions:
- The negative charge is on oxygen, the most electronegative atom.
- The structure has the fewest formal charges overall.
For the middle and bottom structures, the negative charge is placed on nitrogen rather than oxygen, which is less favorable due to nitrogen being less electronegative. Moreover, they introduce a greater charge separation, making them higher in energy.
Thus, the top resonance structure is the most stable and best represents nitrous oxide (N₂O), though the actual molecule is a hybrid of all three.
Now, I’ll generate an image representing the resonance structures.
I’ve generated a scientific diagram illustrating the three resonance structures of nitrous oxide (N₂O), clearly labeling atoms and formal charges. The top structure is marked as the lowest energy. Let me know if you need any modifications!
