Lecture on Molecular Geometry

Introduction

• Presenter: Chad from Chad's Prep
• Focus: Molecular geometry using VSEPR theory
• Courses offered: High school, college prep, MCAT, DAT, OAT
• Access: chadsprep.com
• Lesson: Part of a general chemistry playlist

VSEPR Theory

• Full Form: Valence Shell Electron Pair Repulsion
• Principle: Electrons repel each other to minimize repulsion and energy, increasing stability.
• Electron Domains: Either an atom bonded (single, double, or triple bond) or a non-bonding pair of electrons.
• Key Concept: Electron domains spread out to minimize repulsion.

Electron Domain Geometries

• Types:
  • 2 Domains: Linear, 180°
  • 3 Domains: Trigonal Planar, 120°
  • 4 Domains: Tetrahedral, 109.5°
  • 5 Domains: Trigonal Bipyramidal, 90°, 120°, 180°
  • 6 Domains: Octahedral, 90°, 180°

Molecular Geometry

• Molecular vs. Electron Domain Geometry:
  • They are the same for linear structures.
  • Differ when lone pairs affect the geometry.
  • Example Geometries:
    • Two Domains: Always Linear
    • Three Domains:
      • All bonding: Trigonal Planar
      • One lone pair: Bent shape
      • Non-ideal angles due to lone pair repulsions
    • Four Domains:
      • All bonding: Tetrahedral
      • One lone pair: Trigonal Pyramidal
      • Two lone pairs: Bent
    • Five Domains:
      • All bonding: Trigonal Bipyramidal
      • One lone pair: Seesaw or Sawhorse
      • Two lone pairs: T-Shaped
      • Three lone pairs: Linear
    • Six Domains:
      • All bonding: Octahedral
      • One lone pair: Square Pyramidal
      • Two lone pairs: Square Planar

Key Points

• Bond Angles:
  • Need to factor in lone pairs which cause greater repulsion.
  • Understanding real bond angles deviates from Lewis structures.
• Impact of Lone Pairs:
  • Lone pairs create more repulsion, changing bond angles.
  • Important to remember for trigonal bipyramidal geometry: lone pairs go to equatorial positions to minimize repulsion.

Conclusion

• Memorization: Required for electron domain and molecular geometries.
• Practices: Expect questions where you need to draw Lewis structures first.
• Additional Resources: Quizzes and practice tests available on Chad's Prep.

• Call to Action: Like the video and subscribe for more content.
• Practice Material: General Chemistry Master Course with free trial available.