This document provides an introduction to basic chemistry concepts relevant to forensic investigation, including: - Atoms are composed of protons, neutrons, and electrons. All matter is made of atoms. - The periodic table organizes elements based on atomic number. Compounds are substances made of two or more elements bonded together, such as H2O, CO2, O2, and NH3. - Organic compounds contain carbon and hydrogen, while inorganic compounds involve other elements. Most known compounds are organic. Chemical bonding occurs via ionic or covalent bonds. - Electronegativity and polarity influence a compound's properties and reactivity through intermolecular forces like dipole-dipole interactions