Molecular Geometry and Electron Domains Study Notes
Electron Geometry and Molecular Geometry
Key Definitions and Concepts
- Electron Geometry: The spatial arrangement of all electron domains (bonding and nonbonding) around a central atom.
- Molecular Geometry: The arrangement of only the bonding electron domains around a central atom.
- Electron Domain: A region in space where electrons are most likely to be found; includes bonding pairs and nonbonding pairs (lone pairs).
Types of Electron Geometries and Their Angles
Linear:
- Angle: 180°
- Example: CO2 (two electron domains)
Trigonal Planar:
- Angle: 120°
- Example: BF3 (three electron domains)
Tetrahedral:
- Angle: 109.5°
- Example: CH4 (four electron domains)
Trigonal Bipyramidal:
- Angles: 90° and 120°
- Example: PCl5 (five electron domains)
Octahedral:
- Angle: 90°
- Example: SF6 (six electron domains)
Specific Geometries Based on Electron Domains
Trigonal Bipyramidal Geometry (5 Electron Domains)
Bonding Domains: 5
Nonbonding Domains: 0
Molecular Geometry: Trigonal Bipyramidal
Example: PCl5
Bonding Domains: 4
Nonbonding Domains: 1
Molecular Geometry: Seesaw
Example: SF4
Bonding Domains: 3
Nonbonding Domains: 2
Molecular Geometry: T-shaped
Example: ClF3
Bonding Domains: 2
Nonbonding Domains: 3
Molecular Geometry: Linear
Example: XeF2
Octahedral Geometry (6 Electron Domains)
Bonding Domains: 6
Nonbonding Domains: 0
Molecular Geometry: Octahedral
Example: SF6
Bonding Domains: 5
Nonbonding Domains: 1
Molecular Geometry: Square Pyramidal
Example: BrF5
Bonding Domains: 4
Nonbonding Domains: 2
Molecular Geometry: Square Planar
Example: XeF4
Summary of Fundamental Geometries
- The five fundamental geometries for molecules with 2, 3, 4, 5, or 6 electron groups around a central atom are:
- Linear (2 electron groups)
- Trigonal Planar (3 electron groups)
- Tetrahedral (4 electron groups)
- Trigonal Bipyramidal (5 electron groups)
- Octahedral (6 electron groups)