Boron and aluminium have six electrons in the outermost shell in BF3 and AlCl3. As a result of the electron pair repulsion theory, the shape of the molecules is trigonal planar (flat) with a bond angle of 120° between the B-F and the Al-Cl bonds.
Three and Four Electron Pairs
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Specification: OCR Chemistry A (H032), AS-level, 2.2.2 Bonding and structure. Topic: Shapes and Intermolecular Forces.
Key terms in this lesson
- Electron shell
- A main energy level occupied by electrons, given a principal quantum number n, with n = 1 closest to and lowest in energy relative to the nucleus.
- Electron pair repulsion theory
- The theory that electron pairs around a central atom arrange themselves as far apart as possible to minimise repulsion, determining the shape of a molecule or ion.
More in Shapes and Intermolecular Forces
- Electron Pair Repulsion Theory
- BF3 and SF6 and PCl5
- Polyatomic ions.
- More examples.
- Electronegativity
- Bond Polarity
- Polar Solvents and Solubility
- Induced Dipole-Dipole Interactions (London Forces)
All 13 lessons in Shapes and Intermolecular Forces · All OCR AS-level Chemistry topics