Hexafluorosilicate ion Lewis Structure

Hexafluorosilicate ion Lewis Structure: F₆Na₂Si Lewis Structure, octahedral Geometry, sp3d2 Hybridization & Polarity

Hexafluorosilicate ion Key Facts

The Hexafluorosilicate ion Lewis structure is Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond and Si–F single bond; the central Si has 6 electron domains (0 lone pairs), giving a octahedral electron-domain arrangement and a octahedral molecular geometry with a 90° bond angle. Si is best described as sp3d2-hybridized, and Hexafluorosilicate ion is nonpolar because the bond dipoles cancel by molecular symmetry.

Figure 1: Lewis Structure of Hexafluorosilicate ion (F₆Na₂Si)

Chemical Formula	F₆Na₂Si
CAS Number	16893-85-9
Total Valence Electrons	48
Lewis Structure	Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond and Si–F single bond
Electron-Domain Geometry	octahedral
Molecular Geometry	octahedral
Hybridization Model	sp3d2 (central Si)
Bond Angle	90°
Polarity	Nonpolar molecule

PubChem (CID 28127) and NIST list Hexafluorosilicate ion as F ₆Na ₂Si with CAS 16893-85-9; molecular weight ≈ 188.055 g/mol. View CAS 16893-85-9 dictionary details on Guidechem →

Applications of Hexafluorosilicate ion (CAS 16893-85-9)

Hexafluorosilicate ion 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 "Hexafluorosilicate ion" 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 16893-85-9 as the primary identifier when screening suppliers; always confirm regional availability and safety documentation (SDS).

Step 1 - Valence Electrons & Central Atom

To draw the Hexafluorosilicate ion Lewis structure we first count the total valence electrons. F₆Na₂Si contains 6×7 (F) + 2×1 (Na) + 4 (Si); the net charge of 0 gives a total of 48 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 = 6×7 (F) + 2×1 (Na) + 4 (Si) = 48 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–F single bond, Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond and Si–F 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–F Si–F Si–F Si–F Si–F Si–F

Si: 0 lone pairs, 6 bonding domains

6 bonding domains + 0 lone pairs = 6 electron domains

Expanded Octet: d-Orbital Participation Central Si belongs to period 3 or below, so it can accommodate more than eight electrons: low-lying d orbitals become available and the octahedral arrangement with 6 domains reflects this expanded valence shell. The octet rule alone does not apply to such hypervalent species.

Step 3 - VSEPR Theory & Geometry

VSEPR theory states that the 6 electron domains around Si arrange to minimize mutual repulsion, giving an octahedral 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 octahedral; the Si bond angle is set to 90° 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 sp3d2 hybrid orbitals to form the 6 equivalent electron-domain directions (6 bonding + 0 lone pair).

Formal-charge check

Formal charge on central Si = V − N − ½B = 4 − 0 − ½×12 = -2. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.

Modeling Note Modeling Note: sp3d2 / sp3d2 hybridization is a convenient localized-bond teaching model. Modern quantum-chemical descriptions of hypervalent Hexafluorosilicate ion use molecular orbitals and do not require populated d orbitals as the primary bonding picture.

Is Hexafluorosilicate ion Polar or Nonpolar?

Hexafluorosilicate ion is nonpolar. Although individual Si–terminal bonds are polar when the atoms differ in electronegativity, the octahedral 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. Hexafluorosilicate ion shows the opposite: identical bond dipoles arranged with octahedral 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
Hexafluorosilicate ion	F₆Na₂Si	Si	6	octahedral	Nonpolar
Silicon tetrafluoride	F₄Si	Si	4	tetrahedral	Nonpolar
Silane	H₄Si	Si	4	tetrahedral	Nonpolar

Practice question Starting from the 48 valence electrons of F₆Na₂Si, draw the Lewis structure and confirm the central Si atom is sp3d2-hybridized with octahedral 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 Hexafluorosilicate ion (CAS 16893-85-9)? Browse Supplier on Guidechem →

FAQs

Is F₆Na₂Si polar or nonpolar?

Hexafluorosilicate ion is nonpolar. Its octahedral symmetry cancels the bond dipoles exactly.

What is the Lewis structure of Hexafluorosilicate ion?

Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond, Si–F single bond and Si–F single bond; no lone pairs on Si. It uses all 48 valence electrons and the preferred structure carries a formal charge of -2 on the central atom.

What is the bond angle in Hexafluorosilicate ion?

The Si angle is about 90°. Lone-pair repulsion compresses the angle from the ideal octahedral value.

What is the hybridization of Si in Hexafluorosilicate ion?

The conventional model is sp3d2. Hexafluorosilicate ion has 6 electron domains around the central Si.

What is the CAS number of Hexafluorosilicate ion?

The CAS number is 16893-85-9. PubChem (CID 28127) and NIST identify this with F₆Na₂Si; use it to locate suppliers and database records.

References

PubChem CID 28127, Hexafluorosilicate ion. Molecular formula, CAS number, molecular weight and chemical identity.
NIST Chemistry WebBook, SRD 69, Hexafluorosilicate ion. 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 Hexafluorosilicate ion (CAS 16893-85-9).

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 16893-85-9 identifies the substance, not a universal purity specification.

Make Guideview Preferred Source on Google

Hexafluorosilicate ion Lewis Structure