Notes on Ionic and Covalent Bonding

Overview

• Ionic Bonding: Transfer of electrons between elements, forming ions.
• Covalent Bonding: Sharing of electrons between elements.

Ionic Bonding

• Example: Sodium (Na) + Chlorine (Cl)
  • Sodium has 1 valence electron (Group 1A).
  • Chlorine has 7 valence electrons (Group 7A).
  • Sodium donates its 1 valence electron to chlorine.
• Ion Formation:
  • Sodium loses its electron, acquires a positive charge (Na⁺).
  • Chlorine gains an electron, acquires a negative charge (Cl⁻).
• Electrostatic Force:
  • Opposite charges attract; sodium ion and chloride ion form an ionic bond due to this attraction.

Covalent Bonding

• Example: Hydrogen (H)
  • Hydrogen has 1 valence electron.
  • Needs 2 electrons to fill its outer shell (first shell).
• Bond Formation:
  • Two hydrogen atoms share electrons to achieve stability (H₂).
• Types of Covalent Bonds:
  • Nonpolar Covalent Bond: Equal sharing of electrons.
    • Example: H-H bond.
  • Polar Covalent Bond: Unequal sharing of electrons.
    • Example: H-F bond.
      • Fluorine is more electronegative, pulling electrons closer, resulting in partial charges (H: δ+, F: δ-).

Electronegativity

• Definition: Ability of an atom to attract electrons.
• Polar vs Nonpolar:
  • Polar Covalent: Electronegativity difference ≥ 0.5.
  • Nonpolar Covalent: Electronegativity difference < 0.5.

Practice Problems

1. MgO (Magnesium Oxide):
   • Metal (Mg) + Nonmetal (O) → Ionic.
2. Cl₂ (Chlorine):
   • Same nonmetal → Nonpolar Covalent.
3. NaF (Sodium Fluoride):
   • Metal (Na) + Nonmetal (F) → Ionic.
4. HBr (Hydrogen Bromide):
   • Electronegativity values: H (2.1), Br (2.8) → difference = 0.7 → Polar Covalent.
5. IBr (Iodine Bromide):
   • I (2.5), Br (2.8) → difference = 0.3 → Nonpolar Covalent.
6. C-H bond:
   • C (2.5), H (2.1) → difference = 0.4 → Nonpolar Covalent.
7. OH bond:
   • O (3.5), H (2.1) → difference = 1.4 → Polar Covalent.
8. CaS (Calcium Sulfide):
   • Metal (Ca) + Nonmetal (S) → Ionic.

Conclusion

• Understand the differences between ionic and covalent bonds and recognize bonds based on electronegativity values.
• Remember that oppositely charged ions attract in ionic bonds, while covalent bonds involve shared electrons.