Ionic Bonding Lecture

Introduction to Ionic Bonding

• Ionic Compounds vs Elements
  • Example: Sodium and Chlorine
    • Solid Sodium (Na)
      • Group 1A, metallic, soft, malleable, ductile
      • Conducts electricity
      • Highly reactive with water
    • Chlorine Gas (Cl₂)
      • Diatomic, yellowish-green tint
      • Poisonous if ingested
    • Sodium Chloride (NaCl)
      • Combination of sodium and chlorine
      • Common table salt, safe in small quantities

How Ionic Bonding Works

• Ions Involved: Sodium ion (Na⁺) and Chloride ion (Cl⁻)
• Electrostatic Forces
  • Attraction between oppositely charged ions
  • Known as ionic bond
  • Coulomb's law: opposite charges attract

Structure of Ionic Compounds

• Ionic Crystal Structure
  • Millions of Na⁺ and Cl⁻ ions in a crystal lattice
  • Example of a formula unit: NaCl

Electron Configuration and Ion Formation

Sodium (Na)

• Electron configuration: 1s² 2s² 2p⁶ 3s¹
• Loses the 3s¹ electron to become Na⁺
• Isoelectronic with Neon (Ne)
  • Note: does not change into Neon, remains Na⁺

Chlorine (Cl)

• Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁵
• Gains one electron to become Cl⁻
• Isoelectronic with Argon (Ar)

Naming Ions

• Sodium Ion: Add 'ion' to the metal name
• Chloride Ion: Change nonmetal ending to 'ide'

General Ion Formation Rules

• Metals: Lose electrons to form cations (positive ions)
• Nonmetals: Gain electrons to form anions (negative ions)

Example Problems

Magnesium (Mg)

• Type: Metal
• Loses 2 electrons to form Mg²⁺
• Isoelectronic with Neon

Oxygen (O)

• Type: Non-metal
• Gains 2 electrons to form O²⁻
• Isoelectronic with Neon

Aluminum (Al)

• Type: Metal
• Loses 3 electrons to form Al³⁺
• Isoelectronic with Neon

Periodic Table Guide for Ions

Group Tendencies

• Group 1A: +1 ions
• Group 2A: +2 ions
• Group 3A: +3 ions (excluding semi-metals)
• Group 7A (Halogens): -1 ions
• Group 6A (Chalcogens): -2 ions
• Group 5A: -3 ions

Notes

• Metals = positive ions
• Non-metals = negative ions
• Based on proximity to noble gases

Conclusion

• Understanding ionic bond formation helps with understanding chemical structures and reactions.
• Key concepts: Electron configurations, valence electrons, and periodic table location.