Formamide Lewis Structure

Formamide Lewis Structure: CH₃NO Lewis Structure, trigonal pyramidal Geometry, sp3 Hybridization & Polarity

Formamide Key Facts

The Formamide Lewis structure is N–C single bond and 2 N–H single bond; the central N has 4 electron domains (1 lone pair), giving a tetrahedral electron-domain arrangement and a trigonal pyramidal molecular geometry with a ≈107° bond angle. N is best described as sp3-hybridized, and Formamide is polar because the trigonal pyramidal shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Formamide (CH₃NO)

Chemical Formula	CH₃NO
CAS Number	75-12-7
Total Valence Electrons	18
Lewis Structure	N–C single bond and 2 N–H single bond
Electron-Domain Geometry	tetrahedral
Molecular Geometry	trigonal pyramidal
Hybridization Model	sp3 (central N)
Bond Angle	≈107°
Polarity	Polar molecule

PubChem (CID 713) and NIST list Formamide as CH ₃NO with CAS 75-12-7; molecular weight ≈ 45.041 g/mol. View CAS 75-12-7 dictionary details on Guidechem →

Applications of Formamide (CAS 75-12-7)

This organic compound is used as a solvent, intermediate or specialty reagent in fine-chemical, pharmaceutical and materials synthesis; specify grade and impurity profile when sourcing.

Solvent / Reagent Medium for reactions, extraction or formulation.

Intermediate Building block for downstream derivatives.

Specialty Use Targeted role in pharma/fragrance/materials.

Procurement Note "Formamide" 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 75-12-7 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Formamide Lewis structure we first count the total valence electrons. CH₃NO contains 4 (C) + 3×1 (H) + 5 (N) + 6 (O); the net charge of 0 gives a total of 18 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) + 3×1 (H) + 5 (N) + 6 (O) = 18 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 single bond and 2 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 ×2

N: 1 lone pair, 3 bonding domains

3 bonding domains + 1 lone pairs = 4 electron domains

Octet Rule: Why N Has Eight Electrons N forms 3 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 4 electron domains around N arrange to minimize mutual repulsion, giving an tetrahedral 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 trigonal pyramidal; the N bond angle is set to ≈107° 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 sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (3 bonding + 1 lone pair).

Formal-charge check

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

Modeling Note Modeling Note: sp3 is a compact model for the 4 electron-domain directions around N; full quantum-chemical treatments use molecular orbitals.

Is Formamide Polar or Nonpolar?

Formamide is polar. The trigonal pyramidal 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 Formamide the trigonal pyramidal 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
Formamide	CH₃NO	N	4	trigonal pyramidal	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 18 valence electrons of CH₃NO, draw the Lewis structure and confirm the central N atom is sp3-hybridized with trigonal pyramidal 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 Formamide (CAS 75-12-7)? Browse Supplier on Guidechem →

FAQs

Is CH₃NO polar or nonpolar?

Formamide is polar. Its trigonal pyramidal geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Formamide?

N–C single bond and 2 N–H single bond; one lone pair on N. It uses all 18 valence electrons and the preferred structure carries a formal charge of 2 on the central atom.

What is the bond angle in Formamide?

The N angle is about ≈107°. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.

What is the hybridization of N in Formamide?

The conventional model is sp3. Formamide has 4 electron domains around the central N.

What is the CAS number of Formamide?

The CAS number is 75-12-7. PubChem (CID 713) and NIST identify this with CH₃NO; use it to locate suppliers and database records.

References

PubChem CID 713, Formamide. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Formamide. 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 Formamide (CAS 75-12-7).

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 75-12-7 identifies the substance, not a universal purity specification.

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Formamide Lewis Structure

Formamide Lewis Structure