Draw two electron-dot resonance structures that obey the octet rule for nitrosyl chloride, NOCl (nitrogen is the central atom). Show formal charges, if present, and predict which of the two structures is a more accurate representation of the molecule.
The correct answer and explanation is :
Here is the correct answer for the two electron-dot resonance structures of nitrosyl chloride (NOCl), where nitrogen is the central atom and all atoms obey the octet rule:
Resonance Structures of NOCl:
Structure 1:
- N is single bonded to Cl and double bonded to O.
- Lone pairs:
- Cl has 3 lone pairs.
- O has 2 lone pairs.
- N has 1 lone pair.
- Formal Charges:
- N: 0
- O: 0
- Cl: 0
Structure 2:
- N is single bonded to Cl and triple bonded to O.
- Lone pairs:
- O has 1 lone pair.
- Cl has 3 lone pairs.
- N has no lone pairs.
- Formal Charges:
- N: +1
- O: –1
- Cl: 0
Which is more accurate?
Structure 1 is the more accurate resonance structure.
Explanation (Approx. 300 words):
Nitrosyl chloride (NOCl) is a molecule containing nitrogen (N), oxygen (O), and chlorine (Cl), with nitrogen as the central atom. The molecule consists of a total of 18 valence electrons: 5 from N, 6 from O, and 7 from Cl.
Two major resonance structures that obey the octet rule can be drawn:
- In Structure 1, nitrogen forms a double bond with oxygen and a single bond with chlorine. All atoms have full octets, and the formal charges on each atom are zero. This structure is both electrically neutral and consistent with typical bonding patterns—oxygen commonly forms two bonds and chlorine typically forms one bond with three lone pairs.
- In Structure 2, nitrogen forms a triple bond with oxygen and a single bond with chlorine. This results in nitrogen having a formal charge of +1 and oxygen having a –1 formal charge. Though this still satisfies the octet rule, the separation of charge is energetically less favorable than a neutral structure.
Comparing the two, Structure 1 is the more accurate resonance structure because:
- It has no formal charges, which is typically more stable.
- The bonding and electron distribution better reflect the electronegativities of the atoms.
- It matches experimental data showing a N=O double bond rather than a N≡O triple bond.
Thus, while both structures obey the octet rule and are valid resonance forms, Structure 1 is more stable and contributes more to the actual structure of NOCl.