nocl lewis structure corresponds to Cl–N=O with nitrogen as the central atom, one lone pair on N, two lone pairs on O, and three lone pairs on Cl.
Valence-electron accounting
NOCl (nitrosyl chloride) contains \(18\) valence electrons:
\[ 5\ (\text{N}) + 6\ (\text{O}) + 7\ (\text{Cl}) = 18 \]
Eighteen electrons correspond to \(9\) electron pairs distributed as bonding pairs and lone pairs while satisfying the octet rule for N, O, and Cl.
Bonding pattern and octet check
Nitrogen serves as the central atom in the NOCl Lewis structure because it forms stable multiple bonding with oxygen and a single bond with chlorine. The structure Cl–N=O uses one N–Cl single bond and one N=O double bond.
Octets in Cl–N=O
Chlorine: 1 bond + 3 lone pairs (8 electrons around Cl)
Nitrogen: 3 bonding pairs (one single + one double) + 1 lone pair (8 electrons around N)
Oxygen: 2 bonding pairs (double bond) + 2 lone pairs (8 electrons around O)
Formal charges
Formal charge evaluation uses
\[ FC = V - N - \frac{B}{2} \]
with \(V\) as valence electrons of the free atom, \(N\) as nonbonding electrons on that atom, and \(B\) as bonding electrons shared in bonds.
| Atom | Nonbonding electrons \(N\) | Bonding electrons \(B\) | Formal charge \(FC\) |
|---|---|---|---|
| N | 2 (one lone pair) | 6 (one single + one double) | \(5 - 2 - \frac{6}{2} = 0\) |
| O | 4 (two lone pairs) | 4 (double bond) | \(6 - 4 - \frac{4}{2} = 0\) |
| Cl | 6 (three lone pairs) | 2 (single bond) | \(7 - 6 - \frac{2}{2} = 0\) |
Zero formal charges on all atoms make Cl–N=O the dominant Lewis structure for NOCl under typical general-chemistry conventions.
Resonance and polarity
A secondary resonance description arises by shifting the N=O \(\pi\) electron pair onto oxygen, producing a contributor often written as Cl–N+–O−. This contributor preserves octets while introducing charge separation; it is typically less important than the neutral structure because it contains formal charges.
NOCl is polar because the bonding is not symmetric and the N–O and N–Cl bond dipoles do not cancel in a bent arrangement about nitrogen.
Geometry around nitrogen
Nitrogen in NOCl has three electron domains (N–Cl bond, N=O bond, and one lone pair). The electron-domain geometry is trigonal planar, and the molecular geometry is bent (VSEPR type AX2E) with a bond angle generally smaller than \(120^\circ\) due to lone-pair repulsion.
Lewis diagram visualization
Common pitfalls
- Electron total mismatch: NOCl requires \(18\) valence electrons, not \(16\) or \(20\).
- N–O single-bond-only drawings: a single N–O bond typically forces formal charges (N+, O−) as the main contributor rather than the neutral arrangement.
- Central-atom choice errors: halogen central atoms are uncommon in neutral triatomics when nitrogen and oxygen are present.
- Lone-pair placement omissions: nitrogen in NOCl carries one lone pair in the dominant structure, giving AX2E at nitrogen.