AP Chemistry · Atomic Structure and Properties 1.1 Moles and Molar Mass ↗1.2 Mass Spectra of Elements ↗1.3 Elemental Composition of Pure Substances ↗1.4 Composition of Mixtures ↗1.5 Atomic Structure and Electron Configuration ↗1.6 Photoelectron Spectroscopy ↗1.7 Periodic Trends ↗1.8 Valence Electrons and Ionic Compounds ↗