Page 1: VSEPR Theory and Molecular Shapes

The fundamental principles of molecular geometry are governed by Valence Shell Electron Pair Repulsion (VSEPR) theory. This theory explains how molecules achieve their three-dimensional structures based on electron pair arrangements.

Definition: VSEPR theory states that valence electron pairs arrange themselves to maximize distance between each other due to electrostatic repulsion.

Highlight: The presence of lone pairs significantly affects molecular geometry, creating a distinction between electron domain geometry and molecular geometry.

Example: In a molecule with two bonded atoms and two lone pairs, the electron domain geometry is tetrahedral, but the molecular shape becomes bent.

The relationship between molecular shape and electron arrangement follows specific patterns:

• Linear arrangements occur with two bonded atoms and no lone pairs
• Bent structures form when lone pairs are present
• Trigonal planar and pyramidal shapes depend on the number of bonding atoms and lone pairs

Vocabulary: Electron domain geometry refers to the arrangement of all electron pairs (both bonding and lone pairs) around a central atom.