Disilicon Lewis Structure

Disilicon Lewis Structure: Si₂ Lewis Structure, linear (diatomic) Geometry, sp Hybridization & Polarity

Disilicon Key Facts

The Disilicon Lewis structure is a linear diatomic with a nonpolar bond between its two atoms; because the two atoms are identical, Disilicon is nonpolar.

Figure 1: Lewis Structure of Disilicon (Si₂)

Chemical Formula	Si₂
CAS Number	15660-01-2
Total Valence Electrons	8
Lewis Structure	linear diatomic molecule with one triple bond
Electron-Domain Geometry	linear
Molecular Geometry	linear (diatomic)
Hybridization Model	sp
Bond Angle	180°
Polarity	Nonpolar molecule

PubChem (CID 6327126) and NIST list Disilicon as Si ₂ with CAS 15660-01-2; molecular weight ≈ 56.17 g/mol. View CAS 15660-01-2 dictionary details on Guidechem →

Applications of Disilicon (CAS 15660-01-2)

Disilicon is encountered as a reagent, intermediate or specialty chemical in inorganic, organometallic and materials synthesis. Confirm grade, purity and supplier documentation (SDS) before specifying for a process.

Reagent / Intermediate Used in synthesis and formulation where the substance's reactivity is required.

Specialty Chemical Specified by grade for the intended process or research use.

Sourcing Verify purity, package and regional availability via the CAS identifier.

Procurement Note "Disilicon" 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 15660-01-2 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Disilicon Lewis structure we first count the total valence electrons. Si₂ contains 2×4 (Si); the net charge of 0 gives a total of 8 valence electrons to place.

The central atom is Si. 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 = 2×4 (Si) = 8 electrons.

Step 2 - Lewis Structure & Electron Distribution

Place Si 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: linear diatomic molecule with one triple bond.

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

Si–X

Si: 0 lone pairs, 1 bonding domain

1 bonding domains + 0 lone pairs = 2 electron domains

Octet & Diradical Note In a simple Lewis drawing each atom of this homonuclear diatomic carries lone pairs; species such as O₂ are more accurately described by molecular-orbital theory (paramagnetism arises from unpaired electrons in π* orbitals).

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 2 electron domains around Si arrange to minimize mutual repulsion, giving an linear electron-domain geometry.

Because 0 of these domains are lone pair(s) — and lone pairs repel more strongly than bonding pairs — the observed molecular geometry is linear (diatomic); the Si bond angle is set to 180° 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 0 lone pair(s) on Si, 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, Si uses sp hybrid orbitals to form the 2 equivalent electron-domain directions (1 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Si = V − N − ½B = 4 − 0 − 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: sp is a compact model for the 2 electron-domain directions around Si; full quantum-chemical treatments use molecular orbitals.

Is Disilicon Polar or Nonpolar?

Disilicon is nonpolar. Although individual Si–terminal bonds are polar when the atoms differ in electronegativity, the linear (diatomic) geometry makes their vector sum zero, so there is no net molecular dipole.

Expert Quote — Structural Chemistry Perspective

A common misconception is that polar bonds guarantee a polar molecule. Disilicon shows the opposite: identical bond dipoles arranged with linear (diatomic) symmetry cancel exactly, yielding a nonpolar species.

Interpretation consistent with standard VSEPR / molecular-geometry references.

Its nonpolar character governs solvation and intermolecular behavior; specify grade and handling when sourcing.

Structural Comparison Table

Species	Formula	Central Atom	Electron Domains	Molecular Geometry	Polarity
Disilicon	Si₂	Si	2	linear (diatomic)	Nonpolar
Silicon tetrafluoride	F₄Si	Si	4	tetrahedral	Nonpolar
Silane	H₄Si	Si	4	tetrahedral	Nonpolar

Practice question Starting from the 8 valence electrons of Si₂, draw the Lewis structure and confirm the central Si atom is sp-hybridized with linear (diatomic) 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 Disilicon (CAS 15660-01-2)? Browse Supplier on Guidechem →

FAQs

Is Si₂ polar or nonpolar?

Disilicon is nonpolar. Its linear (diatomic) symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Disilicon?

linear diatomic molecule with one triple bond. It uses all 8 valence electrons and the preferred structure carries a formal charge of 1 on the central atom.

What is the bond angle in Disilicon?

The Si angle is about 180°. Lone-pair repulsion compresses the angle from the ideal linear value.

What is the hybridization of Si in Disilicon?

The conventional model is sp. Disilicon has 2 electron domains around the central Si.

What is the CAS number of Disilicon?

The CAS number is 15660-01-2. PubChem (CID 6327126) and NIST identify this with Si₂; use it to locate suppliers and database records.

References

PubChem CID 6327126, Disilicon. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Disilicon. 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 Disilicon (CAS 15660-01-2).

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 15660-01-2 identifies the substance, not a universal purity specification.

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Disilicon Lewis Structure

Disilicon Lewis Structure