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The Sulfur pentafluoride anion Lewis structure is S–F single bond, S–F single bond, S–F single bond, S–F single bond and S–F single bond; the central S has 6 electron domains (1 lone pair), giving a octahedral electron-domain arrangement and a square pyramidal molecular geometry with a 90° bond angle. S is best described as sp3d2-hybridized, and Sulfur pentafluoride anion is polar because the square pyramidal shape (and/or unequal terminal atoms) prevents cancellation of the bond dipoles.
Figure 1: Lewis Structure of Sulfur pentafluoride anion (F5S)
| Chemical Formula | F5S |
| CAS Number | 16858-16-7 |
| Net Charge | -1 |
| Total Valence Electrons | 42 |
| Lewis Structure | S–F single bond, S–F single bond, S–F single bond, S–F single bond and S–F single bond |
| Electron-Domain Geometry | octahedral |
| Molecular Geometry | square pyramidal |
| Hybridization Model | sp3d2 (central S) |
| Bond Angle | 90° |
| Polarity | Polar molecule |
In aqueous and process chemistry, F5S exists as the anion Sulfur pentafluoride anion ion. It is encountered as a counterion and a controlled source of S in salts, buffers, electrochemistry and analytical protocols, and as a reactant in syntheses that require a defined equivalent of S-containing material.
To draw the Sulfur pentafluoride anion Lewis structure we first count the total valence electrons. F5S contains 5×7 (F) + 6 (S) − 1 (net anion); the net charge of -1 gives a total of 42 valence electrons to place.
The central atom is S. 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 = 5×7 (F) + 6 (S) − 1 (net anion) = 42 electrons.
Place S 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: S–F single bond, S–F single bond, S–F single bond, S–F single bond and S–F single bond; one lone pair on S.
Counting bonding and nonbonding electrons around S therefore satisfies the octet/expanded-octet requirement for the drawn structure.
VSEPR theory states that the 6 electron domains around S arrange to minimize mutual repulsion, giving an octahedral 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 square pyramidal; the S bond angle is set to 90° 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 S, 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, S uses sp3d2 hybrid orbitals to form the 6 equivalent electron-domain directions (5 bonding + 1 lone pair).
Formal charge on central S = V − N − ½B = 6 − 2 − ½×10 = -1. The nonzero formal charge is distributed by resonance / charge separation; the drawn structure is the lowest-energy contributor.
Sulfur pentafluoride anion is polar. The square 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 Sulfur pentafluoride anion the square 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 |
|---|---|---|---|---|---|
| Sulfur pentafluoride anion | F5S | S | 6 | square pyramidal | Polar |
| Sulfur dioxide | SO2 | S | 3 | bent | Polar |
| Sulfur trioxide | O3S | S | 3 | trigonal planar | Nonpolar |
| Sulfur hexafluoride | F6S | S | 6 | octahedral | Nonpolar |
| Sulfur tetrafluoride | F4S | S | 5 | seesaw | Polar |
| Sulfate | O4S | S | 4 | tetrahedral | Nonpolar |
Sulfur pentafluoride anion is polar. Its square pyramidal geometry (and/or unequal terminal atoms) stops the bond dipoles from cancelling.
S–F single bond, S–F single bond, S–F single bond, S–F single bond and S–F single bond; one lone pair on S. It uses all 42 valence electrons and the preferred structure carries a formal charge of -1 on the central atom.
The S angle is about 90°. Lone-pair repulsion compresses the angle from the ideal octahedral value.
The conventional model is sp3d2. Sulfur pentafluoride anion has 6 electron domains around the central S.
The CAS number is 16858-16-7. PubChem and NIST identify this with F5S; 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 16858-16-7 identifies the substance, not a universal purity specification.
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