Chemistry Unit 6 Part 2
1. VSEPR Theory
Q: What is VSEPR theory?
A: Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular shapes based on electron pair repulsion.
Q: What determines molecular shape?
A: The number of bonding and lone pairs around the central atom.
Q: What is the molecular geometry of a molecule with 2 electron domains?
A: Linear (e.g., COâ‚‚)
Q: What is the molecular geometry of a molecule with 3 bonding pairs and 0 lone pairs?
A: Trigonal Planar (e.g., BF₃)
Q: What is the molecular geometry of a molecule with 3 electron domains and 1 lone pair?
A: Bent (e.g., SOâ‚‚)
Q: What is the molecular geometry of a molecule with 4 bonding pairs and 0 lone pairs?
A: Tetrahedral (e.g., CHâ‚„)
Q: What is the molecular geometry of a molecule with 4 electron domains and 1 lone pair?
A: Trigonal Pyramidal (e.g., NH₃)
Q: What is the molecular geometry of a molecule with 4 electron domains and 2 lone pairs?
A: Bent (e.g., Hâ‚‚O)
Q: What is the molecular geometry of a molecule with 5 electron domains?
A: Trigonal Bipyramidal (e.g., PClâ‚…)
Q: What is the molecular geometry of a molecule with 6 electron domains?
A: Octahedral (e.g., SF₆)
VSEPR Notation & Hybridization
Q: What does VSEPR notation look like?
A: AXₙEₘ, where:
• A = central atom
• Xₙ = number of bonding atoms
• Eₘ = number of lone pairs
Q: What is hybridization?
A: The mixing of atomic orbitals to form hybrid orbitals for bonding.
Q: What is the hybridization of a linear molecule?
A: sp
Q: What is the hybridization of a trigonal planar molecule?
A: sp²
Q: What is the hybridization of a tetrahedral molecule?
A: sp³
Q: What is the hybridization of a trigonal bipyramidal molecule?
A: sp³d
Q: What is the hybridization of an octahedral molecule?
A: sp³d²
Molecular Polarity
Q: What determines molecular polarity?
A: Electronegativity differences & molecular shape
Q: What is the general flowchart for molecular polarity?
1. Are there polar bonds?
• No → Nonpolar molecule
• Yes → Continue
2. Is the molecular shape symmetrical?
• Yes → Nonpolar
• No → Polar
Q: What shapes are usually nonpolar if all outer atoms are the same?
A: Linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral
Q: What shapes are usually polar?
A: Bent, trigonal pyramidal, seesaw, T-shaped
4. Bond Angles
Q: What is the bond angle of a linear molecule?
A: 180°
Q: What is the bond angle of a trigonal planar molecule?
A: 120°
Q: What is the bond angle of a tetrahedral molecule?
A: 109.5°
Q: What is the bond angle of a trigonal bipyramidal molecule?
A: 90° and 120°
Q: What is the bond angle of an octahedral molecule?
A: 90°
5. Intermolecular Forces (IMFs)
Q: What are the three types of intermolecular forces?
A: London Dispersion, Dipole-Dipole, Hydrogen Bonding
Q: What are London Dispersion Forces (LDFs)?
A: Weak forces caused by temporary electron shifts. Present in all molecules, but strongest in large nonpolar molecules.
Q: What are Dipole-Dipole forces?
A: Attractions between permanent dipoles in polar molecules.
Q: What is Hydrogen Bonding?
A: A strong dipole-dipole attraction between H and N, O, or F.
Q: Which IMF is the weakest?
A: London Dispersion Forces
Q: Which IMF is the strongest?
A: Hydrogen Bonding
Q: What type of IMF is dominant in water (Hâ‚‚O)?
A: Hydrogen Bonding
Q: What type of IMF is dominant in COâ‚‚?
A: London Dispersion (COâ‚‚ is nonpolar!)
Q: What type of IMF is dominant in HCl?
A: Dipole-Dipole (HCl is polar but does not have hydrogen bonding)