Chemistry: Molecular Shape and Electron Pair Theory

Study Notes

Shape Determination and Electron Pair Repulsion

Electron pairs around a central atom arrange to maximize distance, influencing molecular shape.
Strength of repulsion among electron pairs follows the order: Lone pair-lone pair > Lone pair-bond pair > Bond pair-bond pair.

Charge Distribution

A dipole is a term for a molecule with separated centres of charge.

Molecular Geometry

A trigonal planar molecule typically consists of four atoms.
Angles in molecular shapes:
- Tetrahedral: 109.5 degrees
- Pyramidal: 107 degrees
- V-shaped: 104.5 degrees
- Linear: 180 degrees
- Trigonal planar: 120 degrees

Covalent Bonding

A polar covalent bond occurs when electrons are shared unequally between atoms.
Polar bonds can result in a nonpolar molecule if dipoles are symmetrically arranged.

Molecular Structures and Bond Pairs

Pyramidal molecules contain 1 lone pair and 3 bond pairs.
General shapes based on formulas:
- AX: Linear shape
- AX₂: Linear or V-shaped planar
- AX₃: Trigonal planar or trigonal pyramidal
- AX₄: Tetrahedral shape

Bond Pair and Lone Pair Counts

Linear molecules can have 1 or 2 bond pairs, depending on the number of atoms.
V-shaped molecules consist of 2 bond pairs and 2 lone pairs.
Tetrahedral molecules have 4 bond pairs and 0 lone pairs.
Trigonal planar molecules are characterized by 3 bond pairs and 0 lone pairs.

Description

This quiz covers key concepts related to electron pair repulsion theory and molecular shapes in chemistry. Questions include the ordering of electron pairs and the definition of dipoles. Test your understanding of how the arrangement of electrons influences molecular structure.