Isocyanic acid Lewis Structure

Isocyanic acid Lewis Structure: CHNO Lewis Structure, bent Geometry, sp2 Hybridization & Polarity

Isocyanic acid Key Facts

The Isocyanic acid Lewis structure is N–C double bond and N–H single bond; the central N has 3 electron domains (1 lone pair), giving a trigonal planar electron-domain arrangement and a bent molecular geometry with a ≈119° bond angle. N is best described as sp2-hybridized, and Isocyanic acid is polar because the bent shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Isocyanic acid (CHNO)

Chemical Formula	CHNO
CAS Number	75-13-8
Total Valence Electrons	16
Lewis Structure	N–C double bond and N–H single bond
Electron-Domain Geometry	trigonal planar
Molecular Geometry	bent
Hybridization Model	sp2 (central N)
Bond Angle	≈119°
Polarity	Polar molecule

PubChem (CID 6347) and NIST list Isocyanic acid as CHNO with CAS 75-13-8; molecular weight ≈ 43.025 g/mol. View CAS 75-13-8 dictionary details on Guidechem →

Applications of Isocyanic acid (CAS 75-13-8)

Carboxylic acids and esters are flavors, fragrances, polymers (PET, polyesters, alkyds) and solvents/intermediates; acetate and phthalate esters are plasticizers, and acids are precursors to salts, amides and anhydrides.

Polymers & Resins PET, polyesters and alkyd coatings from acid/ester chemistry.

Solvents & Plasticizers Esters as solvents; phthalates/acetates as flexibilizers.

Flavor & Fine Chem Esters in flavors/fragrances and active-ingredient synthesis.

Procurement Note "Isocyanic acid" is supplied in multiple commercial grades and package sizes. Specify purity, grade, moisture/impurity limits, package (cylinder, drum or bulk) and intended process, and use CAS 75-13-8 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Isocyanic acid Lewis structure we first count the total valence electrons. CHNO contains 4 (C) + 1 (H) + 5 (N) + 6 (O); the net charge of 0 gives a total of 16 valence electrons to place.

The central atom is N. It is the least electronegative atom capable of forming multiple bonds and is surrounded by the more electronegative terminal atom(s); hydrogen, when present, always occupies a terminal position. Electronegativity considerations place the electron density toward the terminal atom(s).

Valence-electron count

Total valence electrons = 4 (C) + 1 (H) + 5 (N) + 6 (O) = 16 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place N at the center and connect each surrounding atom with a single bond, complete octets on the terminal atoms, and place any remaining electrons on the central atom. The resulting electron distribution is: N–C double bond and N–H single bond; one lone pair on N.

Counting bonding and nonbonding electrons around N therefore satisfies the octet/expanded-octet requirement for the drawn structure.

N=C N–H

N: 1 lone pair, 2 bonding domains

2 bonding domains + 1 lone pairs = 3 electron domains

Octet Rule: Why N Has Eight Electrons N forms 2 bond(s) and retains 2 nonbonding electron(s), reaching an octet. No expanded octet is required for this second-row (or octet-satisfying) central atom.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 3 electron domains around N arrange to minimize mutual repulsion, giving an trigonal planar electron-domain geometry.

Because 1 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is bent; the N bond angle is set to ≈119° rather than the ideal value for the electron-domain geometry.

Repulsion hierarchy

A useful VSEPR approximation is: lone pair–lone pair repulsion > lone pair–bonding pair repulsion > bonding pair–bonding pair repulsion. With 1 lone pair(s) on N, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.

Hybridization & Formal Charge

In the conventional localized-bond model, N uses sp2 hybrid orbitals to form the 3 equivalent electron-domain directions (2 bonding + 1 lone pair).

Formal-charge check

Formal charge on central N = V − N − ½B = 5 − 2 − ½×6 = 1. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp2 is a compact model for the 3 electron-domain directions around N; full quantum-chemical treatments use molecular orbitals.

Is Isocyanic acid Polar or Nonpolar?

Isocyanic acid is polar. The bent shape prevents cancellation of the bond dipoles. The bond dipoles do not cancel, leaving a net molecular dipole, which strongly influences solvation behavior and intermolecular interactions.

Expert Quote — Structural Chemistry Perspective

The decisive structural fact is not simply that the individual bonds are polar; it is whether molecular symmetry allows their vector sum to vanish. In Isocyanic acid the bent arrangement prevents cancellation, so a permanent dipole remains.

Interpretation consistent with standard VSEPR / molecular-geometry references.

This polarity profile underpins its behavior as a solvent, reactant or process intermediate; when sourcing, specify grade and container compatibility.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
Isocyanic acid	CHNO	N	3	bent	Polar
Ammonia	H₃N	N	4	trigonal pyramidal	Polar
Ammonium	H₄N	N	4	tetrahedral	Nonpolar
Hydrazine	H₄N₂	N	4	trigonal pyramidal	Polar
Nitrogen	N₂	N	2	linear (diatomic)	Nonpolar
Nitric oxide	NO	N	3	linear (diatomic)	Polar

Practice question Starting from the 16 valence electrons of CHNO, draw the Lewis structure and confirm the central N atom is sp2-hybridized with bent geometry. What happens to the bond angle if one terminal atom is replaced by a more electronegative substituent?

Looking for industrial bulk or specified-grade supplies of Isocyanic acid (CAS 75-13-8)? Browse Supplier on Guidechem →

FAQs

Is CHNO polar or nonpolar?

Isocyanic acid is polar. Its bent geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Isocyanic acid?

N–C double bond and N–H single bond; one lone pair on N. It uses all 16 valence electrons and the preferred structure carries a formal charge of 1 on the central atom.

What is the bond angle in Isocyanic acid?

The N angle is about ≈119°. Lone-pair repulsion compresses the angle from the ideal trigonal planar value.

What is the hybridization of N in Isocyanic acid?

The conventional model is sp2. Isocyanic acid has 3 electron domains around the central N.

What is the CAS number of Isocyanic acid?

The CAS number is 75-13-8. PubChem (CID 6347) and NIST identify this with CHNO; use it to locate suppliers and database records.

References

PubChem CID 6347, Isocyanic acid. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Isocyanic acid. Formula, CAS Registry Number and thermochemical / spectroscopic data.
IUPAC Gold Book. Definitions for "lone pair", "VSEPR", "hybridization" and "formal charge".
Atkins, P. & de Paula, J., Physical Chemistry. VSEPR, molecular geometry and dipole moments.
Guidechem supplier & dictionary records. Commercial sourcing and CAS-linked property pages for Isocyanic acid (CAS 75-13-8).

Technical scope: Lewis structures, VSEPR and hybridization are model-based descriptions for chemical communication and structure prediction; actual molecular electronic structure is more accurately represented by molecular-orbital and quantum-chemical methods. Commercial grades vary substantially by supplier and intended use; CAS 75-13-8 identifies the substance, not a universal purity specification.

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Isocyanic acid Lewis Structure