Determine the electron geometry, molecular geometry, and idealized bond angles for each of the following molecules.
a. CF4
b. NF3
c. OF2
d. H2S
The Correct Answer and Explanation is :
To determine the electron geometry, molecular geometry, and idealized bond angles for the molecules CF₄, NF₃, OF₂, and H₂S, we need to analyze their Lewis structures and consider the VSEPR (Valence Shell Electron Pair Repulsion) theory.
a. CF₄ (Carbon Tetrafluoride)
- Electron Geometry: Tetrahedral
- Molecular Geometry: Tetrahedral
- Idealized Bond Angles: 109.5°
Explanation: Carbon has four valence electrons and forms four single bonds with four fluorine atoms. Since there are no lone pairs on the carbon atom, the electron geometry is tetrahedral, and the molecular geometry remains tetrahedral. The bond angles are approximately 109.5°, typical for tetrahedral geometries.
b. NF₃ (Nitrogen Trifluoride)
- Electron Geometry: Tetrahedral
- Molecular Geometry: Trigonal Pyramidal
- Idealized Bond Angles: Approximately 107°
Explanation: Nitrogen has five valence electrons and forms three single bonds with fluorine atoms, leaving one lone pair on the nitrogen. The presence of the lone pair compresses the bond angles slightly from the ideal tetrahedral angle of 109.5° to approximately 107°, resulting in a trigonal pyramidal molecular geometry.
c. OF₂ (Oxygen Difluoride)
- Electron Geometry: Tetrahedral
- Molecular Geometry: Bent
- Idealized Bond Angles: Approximately 104.5°
Explanation: Oxygen has six valence electrons and forms two single bonds with fluorine, leaving two lone pairs. The tetrahedral electron geometry arises from the four regions of electron density (two bonds and two lone pairs). The lone pairs repel the bonding pairs, leading to a bent molecular shape and reducing the bond angle to approximately 104.5°.
d. H₂S (Hydrogen Sulfide)
- Electron Geometry: Tetrahedral
- Molecular Geometry: Bent
- Idealized Bond Angles: Approximately 104.5°
Explanation: Sulfur has six valence electrons and forms two single bonds with hydrogen, leaving two lone pairs. Similar to OF₂, the four regions of electron density yield a tetrahedral electron geometry, while the two lone pairs cause the molecular geometry to be bent, with bond angles around 104.5°.
Summary Table:
| Molecule | Electron Geometry | Molecular Geometry | Idealized Bond Angles |
|---|---|---|---|
| CF₄ | Tetrahedral | Tetrahedral | 109.5° |
| NF₃ | Tetrahedral | Trigonal Pyramidal | ~107° |
| OF₂ | Tetrahedral | Bent | ~104.5° |
| H₂S | Tetrahedral | Bent | ~104.5° |
Understanding these geometries helps predict molecular behavior and reactivity based on spatial arrangements of atoms.