The approximate bond angles in Aluminum Chloride (AlCl3) are 120 degrees. This value is considered exact for its ideal molecular geometry.
Understanding AlCl3's Geometry and Bond Angles
Aluminum chloride (AlCl3) is a compound whose molecular geometry and bond angles can be predicted using the Valence Shell Electron Pair Repulsion (VSEPR) theory. The central aluminum atom in AlCl3 is bonded to three chlorine atoms and has no lone pairs of electrons.
Key Characteristics
The arrangement of electron pairs around the central aluminum atom determines both the electron geometry and molecular geometry.
- Central Atom: Aluminum (Al)
- Bonded Atoms: 3 Chlorine (Cl) atoms
- Lone Pairs on Central Atom: 0
This configuration leads to a specific shape and corresponding bond angles.
Geometry and Hybridization
Both the electron geometry and molecular geometry of AlCl3 are trigonal planar. This particular arrangement ensures that the electron groups (in this case, the three Al-Cl bonds) are as far apart as possible to minimize repulsion.
The hybridization of the central aluminum atom in AlCl3 is sp2. This hybridization is characteristic of a central atom with three electron domains and no lone pairs, leading directly to a trigonal planar arrangement.
| Feature | Description |
|---|---|
| Bond Angles | 120 degrees |
| Electron Geometry | Trigonal Planar |
| Molecular Geometry | Trigonal Planar |
| Hybridization | sp2 |
Why 120 Degrees?
The 120-degree bond angle arises directly from the trigonal planar molecular geometry. In this geometry:
- The central aluminum atom lies in the same plane as the three chlorine atoms.
- The three Al-Cl bonds are equally spaced around the central aluminum atom.
- This equal spacing results in bond angles of 120 degrees between any two Al-Cl bonds, ensuring maximum separation and minimal repulsion among the electron pairs.
This ideal angle is what VSEPR theory predicts for molecules with a trigonal planar shape.
