Disilyne Lewis Structure

Disilyne Lewis Structure: H₂Si₂ Lewis Structure, linear Geometry, sp Hybridization & Polarity

Disilyne Key Facts

The Disilyne Lewis structure is Si–Si triple bond and Si–H single bond; the central Si has 2 electron domains (0 lone pairs), giving a linear electron-domain arrangement and a linear molecular geometry with a 180° bond angle. Si is best described as sp-hybridized, and Disilyne is polar because the linear shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.

Figure 1: Lewis Structure of Disilyne (H₂Si₂)

Chemical Formula	H₂Si₂
CAS Number	12597-35-8
Total Valence Electrons	10
Lewis Structure	Si–Si triple bond and Si–H single bond
Electron-Domain Geometry	linear
Molecular Geometry	linear
Hybridization Model	sp (central Si)
Bond Angle	180°
Polarity	Polar molecule

PubChem (CID 71420045) and NIST list Disilyne as H ₂Si ₂ with CAS 12597-35-8; molecular weight ≈ 58.19 g/mol. View CAS 12597-35-8 dictionary details on Guidechem →

Applications of Disilyne (CAS 12597-35-8)

As a hydride of Si, Disilyne is typically a strong reducing agent, a potential fuel component, or a precursor in inorganic and organometallic synthesis. Many pnictogen/sulfur hydrides are toxic, foul-smelling and pyrophoric or flammable, and are handled with appropriate ventilation and inert-atmosphere technique.

Reducing Agent Electron-rich hydrides reduce metal centers and functional groups in synthesis.

Precursor / Feedstock Source of Si in the preparation of derivatives and doped materials.

Handling Often toxic/flammable/pyrophoric; inert atmosphere and active ventilation required.

Procurement Note "Disilyne" 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 12597-35-8 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Disilyne Lewis structure we first count the total valence electrons. H₂Si₂ contains 2×1 (H) + 2×4 (Si); the net charge of 0 gives a total of 10 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 = 2×1 (H) + 2×4 (Si) = 10 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: Si–Si triple bond and Si–H single bond; no lone pairs on Si.

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

Si≡Si Si–H

Si: 0 lone pairs, 2 bonding domains

2 bonding domains + 0 lone pairs = 2 electron domains

Octet Rule: Why Si Has Eight Electrons Si forms 2 bond(s) and retains 0 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 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; 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 (2 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Si = V − N − ½B = 4 − 0 − ½×8 = 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 Disilyne Polar or Nonpolar?

Disilyne is polar. The linear 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 Disilyne the linear 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
Disilyne	H₂Si₂	Si	2	linear	Polar
Silicon tetrafluoride	F₄Si	Si	4	tetrahedral	Nonpolar
Silane	H₄Si	Si	4	tetrahedral	Nonpolar

Practice question Starting from the 10 valence electrons of H₂Si₂, draw the Lewis structure and confirm the central Si atom is sp-hybridized with linear 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 Disilyne (CAS 12597-35-8)? Browse Supplier on Guidechem →

FAQs

Is H₂Si₂ polar or nonpolar?

Disilyne is polar. Its linear geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.

What is the Lewis structure of Disilyne?

Si–Si triple bond and Si–H single bond; no lone pairs on Si. It uses all 10 valence electrons and the preferred structure carries a formal charge of 1 on the central atom.

What is the bond angle in Disilyne?

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

What is the hybridization of Si in Disilyne?

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

What is the CAS number of Disilyne?

The CAS number is 12597-35-8. PubChem (CID 71420045) and NIST identify this with H₂Si₂; use it to locate suppliers and database records.

References

PubChem CID 71420045, Disilyne. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Disilyne. 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 Disilyne (CAS 12597-35-8).

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 12597-35-8 identifies the substance, not a universal purity specification.

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Disilyne Lewis Structure

Disilyne Lewis Structure