CHEM 120 Lecture Notes - Lecture 11: Trigonal Bipyramidal Molecular Geometry, Trigonal Planar Molecular Geometry, Atomic Orbital
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Chem 120 Lecture 10/10/18
Section 4-3: Hybridization and the Localized Electron Model
Hybridization: Central Atom with Four Effective Electron Pairs
• One s and three p atomic orbitals hybridize to form four degenerate 𝑠𝑝3 hybrid
orbitals with tetrahedral geometry.
Hybridization: Central Atom with Three Effective Electron Pairs
• One s and two p atomic orbitals hybridize to form three degenerate 𝑠𝑝2 hybrid
orbitals with trigonal planar geometry.
A Carbon-Carbon Double Bond
• Comprised of one sigma and one pi bond
• A sigma bond is formed from the direct, head-on overlap of orbitals along the
direction of the bond
• A pi bond is formed from the lateral, side-on overlap of two orbitals along the
direction of the bond.
Hybridization: Central Atom with Two Effective Electron Pairs
• One s and one p atomic orbital hybridize to form two degenerate sp hybrid
orbitals with linear geometry (180°)
Hybridization: Central Atom with Five Electron Pairs
• One s, three p, and one d atomic orbitals hybridize to form five degenerate 𝑠𝑝3𝑑
hybrid orbitals with trigonal bipyramidal geometry.
Hybridization of Atomic Orbitals for Six Electron Pairs
• One s, three p, and two d atomic orbitals hybridize to form six degenerate
𝑠𝑝3𝑑 hybrid orbitals with octahedral geometry.
Problem-Solving Strategy:
1. Draw Lewis structures
2. Determine the arrangement of electron pairs using the VSEPR model
3. Specify the hybrid orbitals needed to accommodate the electron pairs
Section 4-4: The Molecular Orbital Model
• A molecular orbital is a spatial probability distribution of an electron in a
molecule.
• A bonding molecular orbital has lower energy (more stable) than the atomic
orbitals of which it is composed.
• An antibonding molecular orbital has greater energy (less stable) than the atomic
orbitals of which it is composed.
Molecular Orbital Diagram of Hydrogen Molecule (H2)