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The Methanide ion Lewis structure is 3 C–H single bond; the central C has 4 electron domains (1 lone pair), giving a tetrahedral electron-domain arrangement and a trigonal pyramidal molecular geometry with a ≈107° bond angle. C is best described as sp3-hybridized, and Methanide ion is polar because the trigonal pyramidal shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.
Figure 1: Lewis Structure of Methanide ion (CH3)
| Chemical Formula | CH3 |
| CAS Number | 15194-00-0 |
| Net Charge | -1 |
| Total Valence Electrons | 8 |
| Lewis Structure | 3 C–H single bond |
| Electron-Domain Geometry | tetrahedral |
| Molecular Geometry | trigonal pyramidal |
| Hybridization Model | sp3 (central C) |
| Bond Angle | ≈107° |
| Polarity | Polar molecule |
In aqueous and process chemistry, CH3 exists as the anion Methanide ion ion. It is encountered as a counterion and a controlled source of C in salts, buffers, electrochemistry and analytical protocols, and as a reactant in syntheses that require a defined equivalent of C-containing material.
To draw the Methanide ion Lewis structure we first count the total valence electrons. CH3 contains 4 (C) + 3×1 (H) − 1 (net anion); the net charge of -1 gives a total of 8 valence electrons to place.
The central atom is C. 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).
Total valence electrons = 4 (C) + 3×1 (H) − 1 (net anion) = 8 electrons.
Place C 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: 3 C–H single bond; one lone pair on C.
Counting bonding and nonbonding electrons around C therefore satisfies the octet/expanded-octet requirement for the drawn structure.
VSEPR theory states that the 4 electron domains around C 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 C bond angle is set to ≈107° rather than the ideal value for the electron-domain geometry.
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 C, the lone-pair domains occupy positions that minimize overall repulsion while pushing the bonding domains (and therefore the bonded atoms) closer together.
In the conventional localized-bond model, C uses sp3 hybrid orbitals to form the 4 equivalent electron-domain directions (3 bonding + 1 lone pair).
Formal charge on central C = V − N − ½B = 4 − 2 − ½×6 = 2. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.
Methanide ion 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.
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 Methanide ion 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.
| Species | Formula | Central Atom | Electron Domains | Molecular Geometry | Polarity |
|---|---|---|---|---|---|
| Methanide ion | CH3 | C | 4 | trigonal pyramidal | Polar |
| Carbon dioxide | CO2 | C | 2 | linear | Nonpolar |
| Carbon monoxide | CO | C | 2 | linear (diatomic) | Polar |
| Carbon disulfide | CS2 | C | 2 | linear | Nonpolar |
| Methane | CH4 | C | 4 | tetrahedral | Nonpolar |
| Ethane | C2H6 | C | 4 | tetrahedral | Nonpolar |
Methanide ion is polar. Its trigonal pyramidal geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.
3 C–H single bond; one lone pair on C. It uses all 8 valence electrons and the preferred structure carries a formal charge of 2 on the central atom.
The C angle is about ≈107°. Lone-pair repulsion compresses the angle from the ideal tetrahedral value.
The conventional model is sp3. Methanide ion has 4 electron domains around the central C.
The CAS number is 15194-00-0. PubChem and NIST identify this with CH3; use it to locate suppliers and database records.
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 15194-00-0 identifies the substance, not a universal purity specification.
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