VSEPR Theory and Molecular Geometry: Bond Angles, Polarity, and Intermolecular Forces

VSEPR

Valence Shell Electron Pair Repulsion; it shows molecular shapes by predicting how electron pairs repel.

Linear

2 atoms, 0 lone pairs.

Bent

2 atoms, 1-2 lone pairs.

Trigonal planar

3 atoms, 0 lone pairs.

Tetrahedral

4 atoms, 0 lone pairs.

Trigonal pyramidal

3 atoms, 1 lone pair.

Bond angle - Linear

180°.

Bond angle - Bent

≈ 104.5°.

Bond angle - Trigonal planar

120°.

Bond angle - Tetrahedral

109.5°.

Polarity

Unequal distribution of electrons in a bond causing partial charges.

Determining polarity

Shape (symmetry) and electronegativity difference.

Partial charges in a molecule

The more electronegative atom is δ-; the less is δ+.

Dispersion forces

Weak, all molecules.

Dipole-dipole

Polar molecules.

Hydrogen bonding

H with F, O, N.

Ion-dipole

Ions + polar molecules.

Intermolecular forces

Determine physical properties like boiling point, melting point, solubility, viscosity.

Viscosity

Resistance to flow; depends on intermolecular forces and size.

Cohesion

Attraction between same molecules (water droplets).

Adhesion

Attraction between different substances (water on glass).

States of matter characteristics

Solid (definite shape & volume); Liquid (definite volume only); Gas (no definite shape or volume); Plasma (ionized gas).

Ionic bond

Made of Metal + nonmetal (electron transfer).

Covalent bond

Made of Two nonmetals (shared electrons).

Metallic bond

Made of Metal atoms sharing a 'sea of delocalized electrons.'

Oxidation numbers

Possible charges an element can form in compounds.