Bond Polarity and Dipole Moments Tutorial

Introduction

• Focus on bond polarity and dipole moments.
• Question: How to show bond polarity and dipole moments in various bonds and molecules?

1. Carbon-Oxygen Bond

• Type of Bond: Covalent (both non-metals)
• Electronegativity Values:
  • Carbon: 2.5
  • Oxygen: 3.5
• Electronegativity Difference:
  • Calculation: 3.5 - 2.5 = 1.0
  • Conclusion: Polar covalent bond (difference > 0.5)
• Charge Distribution:
  • Oxygen: Partial negative charge
  • Carbon: Partial positive charge
• Dipole Moment:
  • Arrow from carbon (positive) to oxygen (negative)
• Net Dipole Moment: If present, the molecule is polar; if dipole moments cancel, the molecule is nonpolar.

2. Oxygen-Fluorine Bond

• Type of Bond: Covalent (both non-metals)
• Electronegativity Values:
  • Oxygen: 3.5
  • Fluorine: 4.0
• Electronegativity Difference:
  • Calculation: 4.0 - 3.5 = 0.5
  • Conclusion: Polar covalent bond (difference = 0.5)
• Charge Distribution:
  • Fluorine: Partial negative charge
  • Oxygen: Partial positive charge
• Dipole Moment:
  • Arrow points towards fluorine (most electronegative atom)

3. Sulfur-Hydrogen Bond

• Type of Bond: Covalent (non-metal + non-metal)
• Electronegativity Values:
  • Sulfur: 2.5
  • Hydrogen: 2.1
• Electronegativity Difference:
  • Calculation: 2.5 - 2.1 = 0.4
  • Conclusion: Nonpolar covalent bond
• Charge Distribution:
  • Sulfur: Partial negative charge
  • Hydrogen: Partial positive charge
• Dipole Moment:
  • Arrow points towards sulfur

4. Water (H2O) Molecule

• Lewis Structure: Simple representation
• Electronegativity Values:
  • Oxygen: 3.5
  • Hydrogen: 2.1
• Electronegativity Difference:
  • Calculation: 3.5 - 2.1 = 1.4
  • Conclusion: Polar covalent bond
• Charge Distribution:
  • Oxygen: Partial negative charge
  • Hydrogen: Partial positive charge (two H atoms)
• Dipole Moment:
  • Arrows point towards oxygen
• Molecule Polarity:
  • Net dipole moment exists (Y components do not cancel, but X components do)
  • Conclusion: Water is a polar molecule.

5. Methane (CH4) Molecule

• Structure: Tetrahedral (3D)
• Electronegativity Values:
  • Carbon: 2.5
  • Hydrogen: 2.1
• Electronegativity Difference:
  • Calculation: 2.5 - 2.1 = 0.4
  • Conclusion: Nonpolar bond
• Charge Distribution:
  • Carbon: Partial negative charge (x4 for four H atoms)
  • Hydrogen: Partial positive charge
• Dipole Moment: All arrows cancel out due to symmetrical structure.
• Molecule Polarity:
  • Conclusion: Methane is nonpolar overall.

6. Carbon Dioxide (CO2) Molecule

• Lewis Structure: Simple representation
• Electronegativity Difference:
  • Calculation: 1.0 (polar covalent bond)
• Charge Distribution:
  • Carbon: Partial positive charge
  • Oxygen: Partial negative charge (x2 for two bonds)
• Dipole Moment:
  • Arrows point towards each oxygen, but they cancel each other out.
• Molecule Polarity:
  • Conclusion: Although CO2 has polar bonds, the molecule is nonpolar overall due to the cancellation of dipole moments.