Lecture on Ionic Bonding

Introduction to Ionic Bonding

• Ionic bonding involves the combination of elements to form compounds with different properties.
• Example: Sodium (Na) and chlorine (Cl) combine to form sodium chloride (NaCl), which has properties distinct from its individual elements.

Characteristics of Sodium and Chlorine

• Sodium (Na):
  • Group 1A, metallic, soft, malleable, ductile.
  • Conducts electricity, highly reactive with water.
• Chlorine (Cl):
  • Diatomic gas, yellowish-green tint.
  • Poisonous if ingested.

Formation of Sodium Chloride (NaCl)

• Sodium and chlorine combine to form NaCl, an ionic compound.
• At room temperature, NaCl is a solid and safe to consume in small quantities (table salt).

How Ionic Bonding Works

• Ionic bonds form between oppositely charged ions (e.g., sodium ion and chloride ion).
• Electrostatic attraction (Coulomb's law): Opposite charges attract, same charges repel.
• Ionic bonds form through electrostatic attractive forces in a crystal lattice structure.

Electron Configuration and Ion Formation

• Sodium (Na):
  • Electron configuration: 1s2 2s2 2p6 3s1
  • Loses one electron to form sodium ion (Na+), isoelectronic with neon.
  • Naming: Name of metal + "ion" (no Roman numerals needed).
• Chlorine (Cl):
  • Electron configuration: 1s2 2s2 2p6 3s2 3p5
  • Gains one electron to form chloride ion (Cl-), isoelectronic with argon.
  • Naming: Nonmetal name changes to "-ide" (e.g., chloride).

Types of Ions

• Cations: Positively charged ions formed by metals losing electrons.
• Anions: Negatively charged ions formed by nonmetals gaining electrons.

Examples and Practice

• Magnesium (Mg):
  • Metal, loses 2 electrons to form Mg2+ (isoelectronic with neon).
• Oxygen (O):
  • Non-metal, gains 2 electrons to form oxide ion (O2-).
• Aluminum (Al):
  • Metal, loses 3 electrons to form Al3+.

Periodic Table Trends

• Metals (Groups):
  • Group 1A: +1 ions
  • Group 2A: +2 ions
  • Group 3A: +3 ions (except semi-metals like boron)
• Non-metals (Groups):
  • Group 7A: -1 ions (halogens)
  • Group 6A: -2 ions
  • Group 5A: -3 ions

Summary

• Ionic bonds are determined by electron configurations and the movement towards noble gases.
• Metals and nonmetals form ions based on their position on the periodic table.
• Understanding ionic bonds helps in predicting the behavior and properties of ionic compounds.