Intermolecular forces and covalent structures

Learning objectives

Describe London (dispersion) forces as attractions between instantaneous and induced dipoles, and explain why they strengthen as the number of electrons and the surface contact of the molecules increase

Describe dipole–dipole forces between polar molecules and hydrogen bonding between molecules in which hydrogen is bonded to nitrogen, oxygen or fluorine, and place the three types of intermolecular force in order of strength

Explain trends and anomalies in boiling point, melting point, volatility, viscosity and solubility using the type and strength of the intermolecular forces present, including the anomalous boiling points of water, ammonia and hydrogen fluoride

Predict the solubility of a substance in water and in non-polar solvents by comparing the intermolecular forces broken and formed, and explain why ionic and polar solutes dissolve in polar solvents

Describe the structures and properties of the covalent network substances diamond, graphite, silicon, silicon dioxide and the fullerene C60, relating hardness, melting point and electrical conductivity to the bonding

Explain the separation of a mixture by paper, thin-layer or column chromatography in terms of the relative strength of the interactions of each component with the mobile and the stationary phase, and calculate retardation factor values