Topic overview

Start with the big picture

Atomic number identifies an element, while mass number distinguishes isotopes by their total protons and neutrons; both concepts support elemental analysis and purity testing. Electron configuration and valence electrons help explain ionic charge and oxidation states, which matter in inorganic salts and redox-active therapeutics. Periodic trends can inform expectations about reactivity, solubility, and compatibility. The topic also connects isotopes and radioactive decay with radiopharmaceutical use, and atomic structure with methods such as atomic absorption, ICP-MS, NMR, UV-Vis, and ESR. Further applications include interpreting metal-based drug coordination, assessing stability under thermal or light stress, and understanding the foundations of magnetic resonance and medicinal chemistry.