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 square pyramidal.
Explanation:
- Electron Configuration:
Sulfur (S) has the atomic number 16 and thus has the electron configuration [Ne]3s²3p⁴. When it forms SF₅⁻, sulfur is in the center, bonded to five fluorine atoms. The extra negative charge indicates that sulfur is surrounded by 6 regions of electron density—five single bonds with fluorine atoms and one additional lone pair of electrons. - Electron Density Regions:
In SF₅⁻, the sulfur atom undergoes sp³d² hybridization, which accommodates six electron pairs: five bonding pairs (from the F atoms) and one lone pair. These six regions of electron density are repelled by each other, and according to the VSEPR theory (Valence Shell Electron Pair Repulsion), they will arrange themselves in a way that minimizes repulsion. - Geometry:
The ideal arrangement for six electron pairs around a central atom is octahedral. However, in SF₅⁻, there is one lone pair. Lone pairs occupy more space than bonding pairs, and they tend to distort the molecular geometry. In this case, the lone pair will occupy one of the axial positions, while the five fluorine atoms will occupy the remaining five positions. This leads to a square pyramidal shape, where four fluorine atoms are placed at the equatorial positions, and one fluorine is at the axial position. The lone pair occupies the other axial position, resulting in this geometry. - Bond Angles:
In the square pyramidal geometry, the bond angles between the equatorial fluorine atoms are 90°, and between the axial and equatorial fluorine atoms, the angle is 81.9° (slightly less than 90° due to the presence of the lone pair).
In summary, the molecular geometry around sulfur in SF₅⁻ is square pyramidal, resulting from the presence of five bonding pairs of electrons and one lone pair, which creates an electron distribution that minimizes repulsion.