3.1: Ions - Losing and Gaining Electrons Atoms that lose electrons acquire a positive charge and are called cations. Atoms that gain electrons acquire a negative charge and are called anions. 3.2: Ions-Main Group Elements Ions can be positively charged or negatively charged. An electron dot diagram is used to show how electrons are transferred to make ionic compounds. 3.3: Transition Elements and Ionic Compounds This section begins the formal study of nomenclature, the systematic naming of chemical compounds. Each ionic compound has its own unique name that comes from the names of the ions. 3.4: Polyatomic Ions and Formulae for Ionic Compounds Groups of atoms with an overall charge are called polyatomic ions. Proper chemical formulas for ionic compounds balance the total positive charge with the total negative charge. 3.5: Characteristics of Ionic Compounds-Electrolytes Ionic compounds are composed of cations and anions that are strongly attracted to each other. When dissolved in water, the ions separate from each other, allowing them to form electrolyte solutions. 3.6: Covalent Bonds Water (H₂O) is not an ionic compound; it is not composed of a metal and a nonmetal. A covalent bond is formed between two nonmetals by sharing electrons. 3.7: Multiple Bonds Some molecules must have multiple covalent bonds between atoms to satisfy the octet rule. 3.8: Binary Molecules - Formulae and Names The chemical formula of a simple covalent compound can be determined from its name. The name of a simple covalent compound can be determined from its chemical formula. 3.9: Formula Weight Formula weight of ionic compounds can be determined from the atomic weights of the atoms in their formulas. 3.10: Molecular Weight Molecular weight of covalent compounds can be determined from the atomic weights of the atoms in their formulas. 3.11: Mole-Mass Conversions In a mole-mass conversion or its reverse, a mass-mole conversion, we use the atomic weight of a substance in grams as a conversion factor. 3.12: End of Chapter Problems This problem set is based on Chapter 3 topics.