Chemistry: Molecular Structure, Gas Laws, and States of Matter Review

VSEPR Theory

Electron groups around a central atom repel each other and arrange themselves to be as far apart as possible, determining the molecule's geometry.

Linear Geometry

2 electron groups, 0 lone pairs (180° bond angle, e.g., CO2).

Trigonal Planar Geometry

3 electron groups, 0 lone pairs (120° bond angle, e.g., BF3).

Tetrahedral Geometry

4 electron groups, 0 lone pairs (109.5° bond angle, e.g., CH4).

Trigonal Pyramidal Geometry

4 electron groups, 1 lone pair (≈107° bond angle, e.g., NH3).

Bent/V-shaped Geometry

4 electron groups, 2 lone pairs (≈104.5° bond angle, e.g., H2O).

Hybridization

The mixing of atomic orbitals (s, p, d) to form new hybrid orbitals with equivalent energy for bonding.

sp Hybridization

Linear geometry (2 electron domains).

sp2 Hybridization

Trigonal planar geometry (3 electron domains).

sp3 Hybridization

Tetrahedral geometry (4 electron domains).

Bond Polarity

Determined by the difference in electronegativity between two atoms.

Molecular Polarity

Determined by the overall symmetry of the molecule.

Nonpolar Molecules

Molecules with highly symmetrical shapes where individual bond dipole moments cancel out (e.g., CH4, CO2).

Polar Molecules

Molecules with asymmetrical shapes where bond dipole moments do not cancel, resulting in a net dipole moment (e.g., H2O, NH3).

Intermolecular Forces (IMFs)

Attractive forces between molecules that influence physical properties (boiling point, melting point, viscosity).

London Dispersion Forces (LDF)

Present in all molecules; temporary dipoles created by momentary shifts in electron density.

Dipole-Dipole Forces

Attraction between the positive end of one polar molecule and the negative end of another.

Hydrogen Bonding

A strong type of dipole-dipole force occurring when H is bonded directly to highly electronegative atoms N, O, or F.

Solid State

Definite shape and volume, strong intermolecular forces, and molecular motion is vibration.

Liquid State

Indefinite shape, definite volume, intermediate intermolecular forces, and molecular motion is gliding.

Gas State

Indefinite shape and volume, weak intermolecular forces, and molecular motion is constant random motion.

Melting/Fusion/Thawing

Solid → Liquid; energy is absorbed (endothermic).

Freezing

Liquid → Solid; energy is released (exothermic).

Vaporization

Liquid → Gas; energy is absorbed (endothermic).

Condensation

Gas → Liquid; energy is released (exothermic).

Sublimation

Solid → Gas; energy is absorbed (endothermic).

Dalton's Law of Partial Pressures

The total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases.