Lecture on Ionic and Covalent Bonding

Introduction

• Discusses differences between ionic and covalent bonding.
• Ionic Bonding: Electrons are transferred from one element to another.
• Covalent Bonding: Electrons are shared between elements.

Ionic Bonding

Example: Sodium and Chlorine

• Sodium:
  • One valence electron.
  • Located in Group 1A of the periodic table.
  • Alkali metals are reactive and tend to lose electrons.
• Chlorine:
  • Seven valence electrons.
  • Halogens are reactive non-metals and tend to gain electrons.
• Reaction:
  • Sodium transfers its one valence electron to chlorine.
  • Sodium becomes positively charged; chlorine becomes negatively charged.
  • Opposite charges attract, forming an ionic bond.
  • Ionic bonds result from electrostatic forces between oppositely charged ions.

Covalent Bonding

Example: Hydrogen

• Hydrogen Atoms:
  • Each has one valence electron.
  • Need two electrons to fill their first shell.
• Bond Formation:
  • Sharing of electrons between two hydrogen atoms.
  • Results in a covalent bond (sharing of two electrons).

Types of Covalent Bonds

• Non-Polar Covalent Bonds:
  • Equal sharing of electrons.
  • Example: Bond between two hydrogen atoms.
• Polar Covalent Bonds:
  • Unequal sharing of electrons.
  • Example: Bond between hydrogen and fluorine.
  • Fluorine is more electronegative, pulling electrons closer.
  • Results in a dipole with partial positive and negative charges.

Electronegativity

• Definition: Atom's ability to attract electrons toward itself.
• Higher electronegativity leads to polar covalent bonds.

Practice Problems

Classification of Bonds

• MgO (Magnesium Oxide): Ionic bond (metal + non-metal).
• Chlorine Molecule (Cl2): Non-polar covalent bond (same non-metals).
• Sodium Fluoride (NaF): Ionic bond (metal + non-metal).
• Hydrogen Bromide (HBr): Polar covalent bond (difference in electronegativity > 0.5).
• Iodine Monobromide (IBr): Non-polar covalent bond (electronegativity difference ≤ 0.5).

Additional Examples

• Carbon-Hydrogen Bond: Non-polar covalent bond.
• Oxygen-Hydrogen Bond: Polar covalent bond, example of hydrogen bonding.
• Same Non-Metals (e.g., F-F): Non-polar covalent bond.
• Calcium Sulfide (CaS): Ionic bond (metal + non-metal).

Conclusion

• Understanding of ionic vs covalent bonds.
• Recognizing bonds based on metal/non-metal and electronegativity differences.