VSEPR and Hybridization: Molecular Shapes & Bonding
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VSEPR — Valence Shell Electron Pair Repulsion
Molecular structure — the three-dimensional arrangement of atoms in a molecule.
Molecular structure and electron-pair repulsion
Electron-pair repulsion: electron pairs spread as far apart as possible to minimize repulsion. Unshared (lone) pairs exert an overall effect on the bond angles between shared electron pairs.
Hybridization
Hybridization is the mixing of atomic orbitals to form new hybrid orbitals that are identical in energy and shape. For example, mixing an s orbital and a p orbital produces two sp hybrid orbitals.
The structure around a given atom is determined by minimizing repulsion between electron pairs.
sp hybridization
- Geometry: Linear
- Bonded atoms: Two bonded
- Lone pairs: Zero non-bonded pairs
- AX notation: AX2 or AX2E0
- Polarity: Nonpolar molecule
- Example: BeI2
sp2 hybridization
Two common arrangements with sp2 hybridization:
-
Trigonal planar
- Three bonded
- Zero non-bonded pairs
- AX3 or AX3E0
- Nonpolar molecule
- Example: BCl3
-
Bent (one lone pair)
- Two bonded
- One non-bonded pair
- AX2E or AX2E1
- Polar molecule
- Example: SO2
sp3 hybridization
-
Tetrahedral
- Four bonded
- Zero non-bonded pairs
- AX4 or AX4E0
- Nonpolar molecule (if substituents identical)
- Example: CH4
-
Trigonal pyramidal
- Three bonded
- One non-bonded pair
- AX3E or AX3E1
- Polar molecule
- Example: NH3
-
Bent (two lone pairs)
- Two bonded
- Two non-bonded pairs
- AX2E2
- Polar molecule
- Example: H2O
sp3d hybridization
-
Trigonal bipyramidal
- Five bonded
- Zero non-bonded pairs
- AX5 or AX5E0
- Nonpolar molecule (if substituents arranged symmetrically)
- Example: PCl5
-
See-saw
- Four bonded
- One non-bonded pair
- AX4E or AX4E1
- Polar molecule
- Example: SeF4
-
T-shaped
- Three bonded
- Two non-bonded pairs
- AX3E2
- Polar molecule
- Example: IF3
sp3d2 hybridization
-
Octahedral
- Six bonded
- Zero non-bonded pairs
- AX6 or AX6E0
- Nonpolar molecule (if substituents identical)
- Example: IF6
-
Square pyramidal
- Five bonded
- One non-bonded pair
- AX5E or AX5E1
- Polar molecule
- Example: IF5
-
Square planar
- Four bonded
- Two non-bonded pairs
- AX4E2
- Two non-bonded pairs
- (