Untitled Notes

Definition: Valence bond theory is a quantum mechanical model that describes the formation of bonds between atoms by the overlap of atomic orbitals.
Key Feature: Utilizes hybridization of atomic orbitals to explain molecular geometry and bonding.

Types of Orbitals:
- s Orbitals: Spherical in shape.
- p Orbitals: Dumbbell-shaped, oriented along Cartesian axes (x, y, z).
- d Orbitals: Cloverleaf-shaped, more complex configurations.
Electron Density Map: A three-dimensional representation indicating regions where electrons are likely to be found.

Definition of Hybridization: Mixing of atomic orbitals to form new hybrid orbitals that are degenerate (equal energy).
Types of Hybridization:
- sp: Linear geometry, involving one s and one p orbital (180° angle).
- sp²: Trigonal planar geometry, involving one s and two p orbitals (120° angle).
- sp³: Tetrahedral geometry, involving one s and three p orbitals (109.5° angle).
- sp³d: Trigonal bipyramidal geometry, involving one s, three p, and one d orbital (
  around 90° and 120° angles)
- sp³d²: Octahedral geometry, involving one s, three p, and two d orbitals (90° angles).

Normal Atomic Orbitals: The initial forms before hybridization occurs.
Hybrid Orbitals:
- Example: sp² hybrid orbitals formed from an s orbital and two p orbitals, leading to planar structures.
Bond Formation: Bonds form due to the overlap of orbitals, resulting in:
- Sigma (σ) Bonds: Formed by the end-on overlap of orbitals. e.g.,
- Two s orbitals overlapping.
- Two p orbitals overlapping.
- An s orbital overlapping with a p or hybrid orbital.
- Pi (π) Bonds: Formed from the side-to-side overlap of p orbitals, necessitating their orientation.

Sigma Bonds (σ):
- Can be formed by:
- Overlapping of two s orbitals.
- Overlapping of two p orbitals.
- Overlapping of hybrid orbitals.
- Any combination of the above.
Pi Bonds (π):
- Always formed by the overlap of two unhybridized p orbitals.
- Important in double and triple bonds, contributing to the total bond character of a molecule.

Hybridization of Carbon: sp² hybridization enables carbon to utilize three equivalent orbitals.
Chlorine Contribution: Utilizes a p orbital (3p) for bonding due to its unpaired electron.
Bond Formation: Carbon’s sp² hybrid overlaps with chlorine’s 3p to create sigma bonds.

Formation: Comprising one sigma bond and two pi bonds.
Hybridization: Involves the formation of sp hybrid orbitals from carbon, allowing for triple bond scenarios (e.g., C≡C).

Trigonal Bipyramidal (sp³d): Hybridization that allows molecules with five bonding groups around a central atom.
Octahedral Geometry (sp³d²): Forms from six bonding interactions, with central atoms able to expand their octet (e.g., Iodine).

Electron Group Geometry vs. Molecular Geometry: Need to differentiate between all electron groups (including lone pairs) and the visible structure without lone pairs.
Hybridization and Geometry Relationship:
- 2 Electron Groups ➔ Linear ➔ sp
- 3 Electron Groups ➔ Trigonal Planar ➔ sp²
- 4 Electron Groups ➔ Tetrahedral ➔ sp³
- 5 Electron Groups ➔ Trigonal Bipyramidal ➔ sp³d
- 6 Electron Groups ➔ Octahedral ➔ sp³d²

The understanding of hybridization and valence bond theory is essential for predicting molecular behavior, geometry, and reactivity.
Lewis Structures: Still serve as important tools for visualizing electron arrangements in molecules and understanding hybridization needs.
Real-World Applications: Key in organic chemistry for understanding reactivity patterns of molecules.

Prepare to identify hybridization states based on geometric configurations and count electron groups around central atoms.