Lecture Notes: Ionic and Covalent Bonding

Introduction

• Ionic Bonding: Electrons are transferred from one element to another, typically forming ions.
• Covalent Bonding: Electrons are shared between atoms.

Ionic Bonding

Example: Sodium and Chlorine Reaction

• Sodium (Na):
  • Located in Group 1a of the periodic table (alkali metals).
  • Contains one valence electron.
  • Tends to lose an electron, forming a positively charged ion.
• Chlorine (Cl):
  • Located in Group 7a of the periodic table (halogens).
  • Contains seven valence electrons.
  • Tends to gain an electron, forming a negatively charged ion.
• Bond Formation:
  • Sodium loses one electron to chlorine.
  • Sodium ion (Na⁺) and chloride ion (Cl⁻) are formed.
  • Electrostatic force of attraction binds the ions, forming an ionic bond.

Key Concept

• Electrostatic Attraction: Opposite charges attract each other.

Covalent Bonding

Example: Hydrogen Molecule

• Hydrogen (H):
  • Has one valence electron.
  • Needs two electrons to fill the outer shell (first row of the periodic table).
  • Shares electrons to form covalent bonds.

Types of Covalent Bonds

• Nonpolar Covalent Bonds:
  • Equal sharing of electrons.
  • Example: Bond between two hydrogen atoms.
• Polar Covalent Bonds:
  • Unequal sharing of electrons.
  • Example: Hydrogen and Fluorine bond.
  • Fluorine is more electronegative, pulling electrons closer.
  • Formation of partial charges and dipoles.

Electronegativity

• Definition: The ability of an atom to attract electrons.
• Important in determining bond polarity.
• Polar Covalent Bond: Electronegativity difference ≥ 0.5.
• Nonpolar Covalent Bond: Electronegativity difference < 0.5.

Practice Problems

Determine Bond Type

1. MgO (Magnesium Oxide):
   • Ionic bond (metal + nonmetal).
2. Cl-Cl (Chlorine Molecule):
   • Nonpolar covalent bond (same elements).
3. NaF (Sodium Fluoride):
   • Ionic bond (metal + nonmetal).
4. HBr (Hydrogen Bromide):
   • Polar covalent bond (different elements, EN difference > 0.5).
5. Iodine Monobromide (IBr):
   • Nonpolar covalent bond (EN difference < 0.5).
6. C-H (Carbon-Hydrogen):
   • Nonpolar covalent bond (common in chemistry).
7. O-H (Oxygen-Hydrogen):
   • Polar covalent bond (hydrogen bonding involved).
8. CaS (Calcium Sulfide):
   • Ionic bond (metal + nonmetal).

Notes

• Use electronegativity tables for precise calculations.
• Recognize common bond types for quick identification.

Conclusion

• Ionic Bonds: Result from the transfer of electrons and electrostatic attraction.
• Covalent Bonds: Result from the sharing of electrons, can be polar or nonpolar.
• Understanding these concepts is essential for classifying and predicting bond types.

• Review this guide to reinforce the concepts of ionic and covalent bonding.