Sulfur Tetrafluoride, SF4 Lewis Structure 3-D Molecular Structure Number of Valence Electrons Steric Number of Central Atom Electron Group Geometry/ Hybridization Molecular Geometry Bond Angle(s) Polar? (If yes, show dipole on 3-D structure)
The correct answer and explanation is:
Sure! Here’s the complete analysis for Sulfur Tetrafluoride (SF₄) including its Lewis structure, molecular geometry, hybridization, polarity, and more.
1. Lewis Structure of SF₄
- Sulfur (S) is the central atom.
- Fluorine (F) forms 4 single bonds with Sulfur.
- Sulfur has one lone pair.
- Each F has 3 lone pairs.
Total Valence Electrons:
- Sulfur: 6
- Fluorine (×4): 7 × 4 = 28
Total = 6 + 28 = 34 electrons
Use:
- 4 S–F bonds × 2 e⁻ = 8 e⁻
- 1 lone pair on S = 2 e⁻
- 4 F atoms × 3 lone pairs = 24 e⁻
Total = 8 + 2 + 24 = 34 e⁻ ✅
2. Steric Number of Central Atom (Sulfur):
- 4 bonded atoms + 1 lone pair = 5
3. Electron Group Geometry / Hybridization:
- Electron geometry: Trigonal bipyramidal
- Hybridization: sp³d
4. Molecular Geometry (Shape):
- See-saw shape, due to one lone pair occupying an equatorial position to reduce electron pair repulsion.
5. Bond Angles:
- Axial–equatorial bonds: ~90°
- Equatorial–equatorial bonds: ~120°
- Lone pair–bond angle distortions: Angles slightly less than ideal due to lone pair repulsion.
6. Polarity:
- Polar molecule
- The lone pair on S and asymmetric shape create a net dipole moment.
- Dipoles from S–F bonds do not cancel out.
7. 3D Structure Description:
In 3D, SF₄ looks like a distorted trigonal bipyramid:
- Two F atoms in equatorial positions.
- Two F atoms in axial positions.
- Lone pair occupies the remaining equatorial position.
- The molecule appears asymmetrical, which contributes to its polarity.
Explanation (300 words):
Sulfur tetrafluoride (SF₄) is a molecule with five electron domains around the central sulfur atom, consisting of four bonding pairs and one lone pair. These five regions of electron density give SF₄ a steric number of 5, indicating sp³d hybridization. This results in a trigonal bipyramidal electron geometry. However, the presence of one lone pair on sulfur alters the ideal shape, making the molecular geometry a see-saw.
In a trigonal bipyramidal structure, electron pairs prefer equatorial positions over axial ones due to lower electron repulsion. Thus, the lone pair resides in one of the equatorial positions, minimizing repulsion with bonded fluorine atoms. As a result, the molecule adopts a see-saw shape, not a symmetric geometry.
The Lewis structure shows sulfur bonded to four fluorine atoms with one lone pair. Fluorine, being highly electronegative, pulls electron density toward itself in each S–F bond. However, due to the molecule’s asymmetric shape, the individual bond dipoles do not cancel out, making SF₄ a polar molecule. The presence of a net dipole moment is supported by its bent geometry and uneven charge distribution.
Bond angles in SF₄ deviate slightly from ideal due to lone pair repulsion: axial F–S–equatorial bond angles are close to 90°, and equatorial F–S–F angles are near 120°, but slightly less due to the lone pair pushing the bonding pairs closer together.
Overall, SF₄ is a well-known example of a molecule with expanded octet on sulfur and a molecular geometry influenced by lone pair-bond pair repulsions. Its polar nature makes it important in chemical synthesis and as a fluorinating agent.