Lecture Notes: 7.1 Ionic Bonding - OpenStax Chemistry 2e

Key Concepts

• Ions and Ionic Compounds:
  • Ions are charged atoms or molecules.
  • Cations: Positive ions formed by losing electrons.
  • Anions: Negative ions formed by gaining electrons.
  • Ionic Compounds (Salts): Composed of cations and anions held together by ionic bonds (electrostatic attraction).

Properties of Ionic Compounds

• Crystalline Structure: Rigid and brittle.
• High Melting and Boiling Points: Strong ionic bonds.
• Conductivity: Poor conductors in solid state, but good conductors when dissolved in water as ions move freely.

Formation of Ionic Compounds

• Binary Ionic Compounds: Composed of two elements, typically a metal (cation) and a nonmetal (anion).
• Charges and Formulas:
  • Metal atoms lose electrons (low ionization potential), nonmetals gain electrons (high electron affinity).
  • Compounds must be electrically neutral.
  • Formula represents the simplest ratio of ions (e.g., Al₂O₃).
  • Does not represent physical arrangement of ions.
  • Sodium chloride (NaCl) example: Sodium (cation) and Chlorine (anion) form a lattice.

Electronic Structures

• Cations:

  • Main group elements lose valence electrons to become isoelectronic with preceding noble gas.
  • Transition metals often lose s electrons first, form ions like Fe²⁺, Fe³⁺.

• Anions:

  • Nonmetals gain electrons to fill outer s and p orbitals to become isoelectronic with next noble gas.

Example Problems

• Example 7.1: Determining electron configurations for cations like Cr³⁺ and Zn²⁺.
• Example 7.2: Determining electron configurations for anions like Se²⁻ and I⁻.

Learning Objectives

• Explain formation of cations, anions, and ionic compounds.
• Predict charges of elements and write electron configurations.

Note: These notes summarize the key points from the lecture on ionic bonding in chemistry, as provided by OpenStax.