Chapter 9: Models of Chemical Bonding

Students learn how ionic bonds form between metals and nonmetals through electron transfer, creating oppositely charged ions that attract electrostatically. Covalent bonding, on the other hand, involves the sharing of electrons between nonmetals, and the chapter explores how atoms form single, double, or triple bonds to complete their valence shells. Lewis symbols are used to visualize valence electrons, and the octet rule is presented as a guiding principle in predicting bonding behavior. Students practice drawing Lewis structures for simple molecules and polyatomic ions, including cases with multiple bonds and resonance structures. The concept of electronegativity is introduced to explain bond polarity, leading to a discussion of polar and nonpolar covalent bonds and the formation of molecular dipoles. The chapter also explores the relationship between bond length, bond strength, and bond order, helping students compare different types of bonds and predict molecular stability. Exceptions to the octet rule are addressed, including molecules with expanded valence shells or odd numbers of electrons. The role of formal charge is explained as a tool for evaluating the most stable resonance structures. Throughout the chapter, students learn how atomic properties such as size, ionization energy, and electronegativity influence bonding, and how the arrangement of electrons determines molecular geometry and reactivity. These concepts lay the groundwork for understanding molecular shape, hybridization, and intermolecular forces in later chapters.