Lecture Notes: Lewis Dot Structures and Ionic Bonding

Lewis Dot Structures

• Definition: Representation of valence electrons around atoms as dots.
• Neutral Atom vs Anion:
  • Neutral atom: original configuration.
  • Anion example: Group 15 element as a -3 anion achieving noble gas configuration with 8 electrons.
• Naming: Named after Gilbert N. Lewis.

Ionic Compounds

• Covalent vs Ionic Compounds:
  • Covalent: Bonding occurs between non-metals (e.g., Group 15 with Group 13).
  • Ionic: Bonding between a metal (Group 1 or 2) and a non-metal.
• Formation: Involves electron transfer and Coulomb’s law.
  • Example: Sodium (Na) donating an electron to Chlorine (Cl) to form NaCl (sodium chloride).
• Binary Compounds: Composed of one metal cation and one non-metal anion, typically found as solids.
• Lattice Structure and Energy:
  • Lattice Energy: Energy required to separate ions in a solid; influences stability.

Ionic Bonding and Energy

• Ionization Energy: Energy needed to remove an electron from an atom.
• Electron Affinity: Energy change when an electron is added to an atom.
• Lattice Energy Calculation:
  • Based on ions' charges and distances between nuclei (Coulomb’s law).

Chemical Nomenclature

• Ions Naming:
  • Cations: Element name + "ion" (e.g., Potassium ion, Calcium ion).
  • Transition Metals: Use Roman numerals to indicate charge (e.g., Iron (II) ion).
  • Anions: Change element ending to "-ide" + "ion" (e.g., Chloride ion).
• Common Ions:
  • Group 1, 2 metals have constant charges.
  • Transition metals have variable charges.

Writing Formulas for Ionic Compounds

• Examples:
  • Aluminum oxide: Al₂O₃.
  • Potassium bromide: KBr.
• Balance Charges: Ensure total charges balance to zero.

Polyatomic Ions

• Definition: Ions composed of multiple atoms bonded covalently.
• Important Polyatomic Ions to Remember:
  • Ammonium (NH₄⁺), Hydroxide (OH⁻), Nitrate (NO₃⁻), Sulfate (SO₄²⁻).
• Formulas with Polyatomic Ions:
  • Use parentheses for polyatomic ions with subscripts (e.g., Calcium phosphate: Ca₃(PO₄)₂).

Practice and Application

• Naming and Writing Formulas:
  • Understand charges based on periodic table position.
  • Use Roman numerals for transition metals’ charges.
  • Practice writing formulas and balancing charges.
• Polyatomic Ions in Compounds:
  • Keep ion structure intact with parentheses where needed.

Conclusion

• Understanding Nomenclature and Formulas: Essential for identifying and naming ionic compounds accurately.
• Memorization: Key polyatomic ions and transition metal charges need to be memorized for practical applications.