Hybridization: Mixing of atomic orbitals to form new hybrid orbitals; determines electron domain geometry.
Electron Geometry (arrangement of all electron domains) differs from Molecular Geometry (arrangement of atoms) if lone pairs are present.
Common geometries include Linear (sp), Trigonal planar (sp2), Tetrahedral (sp3), Trigonal bipyramidal (sp3d), and Octahedral (sp3d2).
Must-Know Formula / Reaction
Steric Number (SN) = (Number of ฯ bonds) + (Number of lone pairs on central atom)
SN 2 โ sp hybridization โ Linear electron geometry
SN 3 โ sp2 hybridization โ Trigonal planar electron geometry
SN 4 โ sp3 hybridization โ Tetrahedral electron geometry
SN 5 โ sp3d hybridization โ Trigonal bipyramidal electron geometry
SN 6 โ sp3d2 hybridization โ Octahedral electron geometry
Note: Only sigma (ฯ) bonds contribute to steric number, not pi (ฯ) bonds.
Common Mistakes
Students often confuse electron geometry with molecular geometry, especially when lone pairs modify the shape.
Don't forget to correctly count lone pairs on the central atom while calculating the steric number.
Incorrectly assuming bond angles are always ideal (e.g., 109.5ยฐ for sp3) without considering lone pair repulsion.
Rapid Revision
Mastering VSEPR and Hybridization is key for predicting molecular shapes. Remember that lone pairs exert greater repulsion, causing deviations from ideal bond angles. Quickly calculate the steric number (ฯ bonds + lone pairs) to determine hybridization and electron geometry, then derive the molecular geometry.
Frequently Asked Questions
What is the main principle of VSEPR theory?โพ
VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion, thus determining the molecular geometry. Lone pairs exert more repulsion than bond pairs.
How does hybridization influence molecular geometry?โพ
Hybridization involves the mixing of atomic orbitals to form new hybrid orbitals that are suitable for bonding. The number and type of hybrid orbitals determine the electron domain geometry around the central atom, which in turn dictates the molecular geometry.
What is the distinction between electron geometry and molecular geometry?โพ
Electron geometry refers to the arrangement of all electron domains (both bonding and non-bonding/lone pairs) around the central atom. Molecular geometry, however, describes the arrangement of only the atoms in space, considering the effects of lone pairs on the shape but not including them as part of the shape's description.
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