From particles to measurable properties
A material's properties are not determined by its formula alone. A reliable explanation follows a chain of levels: composition and electron structure -> bonding and local geometry -> organization of particles -> microstructure and defects -> observable properties. Each arrow indicates influence, not an absolute guarantee. Temperature, pressure, purity, processing history and measurement direction may also matter.
1. Composition, electrons, bonding and geometry
Valence electrons and electronegativity help predict ionic, covalent or metallic bonding. Bond polarity and molecular geometry together determine molecular polarity. Ionic lattices contain oppositely charged ions; network covalent solids contain extended covalent bonds; molecular substances consist of molecules held together by intermolecular forces; metals contain positive ion cores and mobile delocalized electrons.