what is the molecular geometry around sulfur in SF4 ?
The correct answer and explanation is :
The molecular geometry around sulfur in SF₄ (sulfur tetrafluoride) is see-saw.
Explanation:
SF₄ is a molecule that contains sulfur (S) at its center, surrounded by four fluorine (F) atoms. The molecular geometry is determined by the electron pair repulsion theory (VSEPR theory), which takes into account both bonding pairs and lone pairs of electrons around the central atom.
- Valence Shell Electron Pair Repulsion (VSEPR) Theory:
- Sulfur (S) is in group 16 of the periodic table and has 6 valence electrons. Each fluorine (F) atom is in group 17, with 7 valence electrons.
- The molecule has 4 bonding pairs (each F atom bonds with the sulfur) and 1 lone pair of electrons on the sulfur atom.
- Electron Domains:
According to VSEPR theory, the electron pairs around a central atom repel each other and will arrange themselves to minimize this repulsion. In SF₄, sulfur has 5 electron domains: 4 bonding pairs (from the fluorine atoms) and 1 lone pair. - Electron Pair Geometry:
The electron pair geometry for 5 electron pairs is a trigonal bipyramidal geometry. In this arrangement, there are two axial positions (above and below the sulfur) and three equatorial positions (in the plane of the sulfur). - Molecular Geometry:
Since there is a lone pair of electrons, it occupies one of the equatorial positions to minimize the repulsion between electron pairs. The fluorine atoms occupy the remaining positions. The result is a see-saw shape, where two fluorine atoms occupy the axial positions and two occupy the equatorial positions. - Bond Angles:
The bond angles in SF₄ are not exactly the same as those in a trigonal bipyramidal structure due to the presence of the lone pair. The axial positions have bond angles of approximately 90°, and the equatorial positions have bond angles of around 120°.
In summary, the geometry around sulfur in SF₄ is see-saw due to the 5 electron domains and the lone pair of electrons, which causes the structure to deviate from a perfect trigonal bipyramidal geometry.