what is the molecular geometry around sulfur in SF5- ?
The correct answer and explanation is :
The molecular geometry around sulfur in the SF₅⁻ ion is trigonal bipyramidal.
Explanation:
The SF₅⁻ ion consists of a sulfur atom bonded to five fluorine atoms and carries a negative charge. To determine the geometry, we can use the Valence Shell Electron Pair Repulsion (VSEPR) theory, which helps predict the arrangement of atoms and electron pairs around a central atom based on their repulsion.
- Electron Domains: The sulfur atom in SF₅⁻ has 5 bonding pairs of electrons (from the 5 fluorine atoms) and 1 additional electron from the negative charge. This gives a total of 6 electron domains (5 bonding pairs + 1 lone pair).
- Electron Geometry: According to VSEPR theory, a molecule with 6 electron domains around the central atom adopts an octahedral electron geometry. The electron pairs in this geometry are arranged at 90° and 180° angles to minimize repulsion.
- Molecular Geometry: In SF₅⁻, the sulfur atom has 5 bonding pairs and 1 lone pair. When there is one lone pair of electrons, it usually occupies an axial position (due to less repulsion in these positions), leaving the five fluorine atoms in the equatorial positions. This arrangement leads to a trigonal bipyramidal molecular geometry.
- Effect of the Negative Charge: The negative charge on SF₅⁻ is localized on the sulfur atom, which doesn’t significantly alter the geometry. The lone pair doesn’t cause a major distortion, as it occupies one of the axial positions, and the fluorine atoms are arranged symmetrically around the sulfur.
- Bond Angles: The bond angles in SF₅⁻ are slightly less than 90° for the equatorial positions and slightly less than 120° for the axial-equatorial interactions due to the lone pair’s repulsion.
In summary, the molecular geometry of SF₅⁻ is trigonal bipyramidal, with 5 fluorine atoms arranged around the sulfur atom in this specific geometry.