Lecture on Ionic and Covalent Bonding

Introduction

• Discussion on the difference between ionic and covalent bonding.

Ionic Bonding

• Definition: Transfer of electrons from one element to another; typically forms ions.
• Example: Sodium (Na) and Chlorine (Cl).
  • Sodium has 1 valence electron (Group 1A, very reactive metal).
  • Chlorine has 7 valence electrons (Group 7A, halogen, very reactive non-metal).
  • Sodium loses its valence electron becoming positively charged.
  • Chlorine gains an electron becoming negatively charged.
• Physics of Bonds:
  • Like charges repel; opposite charges attract.
  • Sodium ion (+) is attracted to Chloride ion (-) forming an ionic bond.
  • Key Point: Ionic bonds are due to electrostatic forces between opposite charges.

Covalent Bonding

• Definition: Sharing of electrons between atoms.
• Hydrogen Example:
  • Hydrogen has 1 valence electron, needs 2 to fill its outer shell.
  • Two hydrogen atoms share electrons, forming a covalent bond.
  • Bond: Represents sharing of two electrons (covalent bond).
• Types of Covalent Bonds:
  • Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., between two hydrogen atoms).
  • Polar Covalent Bonds: Unequal sharing due to electronegativity differences (e.g., Hydrogen and Fluorine).
    • Fluorine is more electronegative; pulls electrons towards itself.
    • Results in partial negative charge on Fluorine, partial positive on Hydrogen.
    • Dipole: One side positive, one negative due to unequal charge distribution.

Electronegativity

• Definition: Ability of an atom to attract electrons.
• Fluorine is highly electronegative.

Practice Problems

• Classification: Determine if bonds are ionic, polar covalent, or non-polar covalent.
  • MgO (Magnesium Oxide): Ionic (metal and nonmetal).
  • Cl₂ (Two Chlorines): Nonpolar covalent (same nonmetals).
  • NaF (Sodium Fluoride): Ionic (metal and nonmetal).
  • HBr (Hydrogen Bromide): Polar covalent (different elements, difference in electronegativity).
  • Iodine Monobromide: Check EN difference (0.3, so nonpolar covalent).
  • Carbon and Hydrogen: Nonpolar (EN difference 0.4).
  • OH (Oxygen-Hydrogen): Polar covalent (large EN difference).
  • CaS (Calcium Sulfide): Ionic (metal and nonmetal).

Conclusion

• Understanding the differences between ionic and covalent bonds is crucial.
• Use periodic table positions and electronegativity values for determination.

Note: Use electronegativity tables provided in textbooks for accurate calculations and classifications.