CH103 - Chapter 4: Ions and Ionic Compounds - Chemistry

4.1 Introduction to the Octet Rule

• Atoms are neutrally charged with equal electrons & protons.
• Ions: Charged particles due to electron transfer.
• Octet Rule: Atoms tend to have eight valence electrons.
  • Cations: Lose electrons, become positive.
  • Anions: Gain electrons, become negative.
• Ionic Bonds: Attraction between cations and anions.
• Electron-Dot Symbols: Graphical notation of valence electrons using dots around the element symbol.

4.2 Ions and the Periodic Table

• Metals (left side): Lose electrons to mimic previous noble gas configuration.
• Nonmetals (right side): Gain electrons to mimic next noble gas.
• Common Ions:
  • Group IA: +1 charge (e.g., Na → Na⁺).
  • Group IIA: +2 charge.
  • Group IIIA: +3 charge.
  • Group VIIA: -1 charge (e.g., Cl → Cl⁻).
  • Group VIA: -2 charge.
  • Group VA: -3 charge.
• Transition Metals: Variable charges, check periodic table.

4.3 Ionic Bonding

• Ionic Compounds: Electrically neutral, formed from cations and anions (e.g., NaCl).
• Formation:
  • Cations donate electrons to anions.
  • Binary Ionic Compounds: Two atoms, one cation, one anion.
  • Example: NaCl formation via electron transfer from Na to Cl.

4.4 Practice Writing Correct Ionic Formulas

• Steps:
  1. Know ion charges.
  2. Determine ratio for neutral charge.
  3. Cation first, anion second.
  4. Write formula with simplest ratio.
• Charge Box Method: Helps determine correct ratios and charges.

4.5 Naming Ions and Ionic Compounds

• Cations: Element name + "ion".
• Anions: Element name ending in "-ide" + "ion".
• Compounds:
  • Name cation first, anion second.
  • Use Roman numerals for cations with multiple charge states (e.g., iron(III) chloride).

4.6 Polyatomic Ions

• Definition: Ions with multiple atoms bonded covalently, acting as one ion (e.g., PO₄³⁻).
• Naming: Similar to simple ions, can be recognized by non-ide endings (e.g., -ate, -ite).
• Examples: Sodium phosphate (Na₃PO₄).

4.7 Naming Polyatomic Ions

• Oxyanions: Contain oxygen, named with -ate or -ite suffixes.
• Prefixes: hypo- (less oxygen), per- (more oxygen).
• Example: ClO₄⁻ = perchlorate.

4.8 Properties and Types of Ionic Compounds

• Structure: Form crystalline lattices (e.g., NaCl lattice).
• Properties:
  • High melting/boiling points.
  • Hard and brittle.
  • Conduct electricity when melted/dissolved (electrolytes).

4.9 Arrhenius Acids and Bases

• Definitions:
  • Acids: Increase H⁺ concentration in solution.
  • Bases: Increase OH⁻ concentration.
• Naming:
  • Binary acids: "hydro-" prefix + "-ic acid".
  • Polyatomic acids: Use anion name + "-ic" or "-ous acid".

4.10 Ions, Neurons, and Action Potentials

• Neurons: Electrically excitable, send signals via action potentials.
• Structure: Cell body, dendrites, axon.
• Action Potential Process:
  • Resting potential at -70 mV.
  • Sodium/Potassium pump maintains ion gradient.
  • Depolarization triggers action potential.
  • Neurotransmitters released at synapse.

4.11 Chapter Summary

• Ions: Cations (positive, metal) and anions (negative, nonmetal).
• Ionic Bonds: Formed by attraction between opposite charges.
• Naming and Formula Writing: Systematic, using ion charges and naming conventions.
• Neurons: Use ion gradients for signaling, action potentials facilitated by ion channels.

4.12 References

• List of literature and resources for further reading.