VSEPR Theory and Molecular Geometry Quiz

VSEPR Theory and Molecular Geometry

• VSEPR theory predicts molecular geometry based on electron repulsion.
• Common geometries include linear (180°), trigonal planar (120°), tetrahedral (109.5°), trigonal bipyramidal (90°/120°), and octahedral (90°).
• Use Lewis structures to count bonding and lone pairs around the central atom to determine shape.
• Examples: Water (bent, 104.5°) and methane (tetrahedral, 109.5°).

Intermolecular Forces (IMFs) vs. Intramolecular Forces

• IMFs are forces between molecules (weaker).
• Types of IMFs: London Dispersion (all molecules), Dipole-Dipole (polar molecules), Hydrogen Bonding (H with N, O, F).
• Intramolecular forces are bonds within molecules (stronger), such as covalent, ionic, or metallic bonds.

Polarity of Molecules

• Polar molecules have asymmetrical electron distribution (asymmetrical dipoles).
• Nonpolar molecules have symmetrical electron distribution.
• Dipoles point towards the more electronegative atom.
• Partial charges are assigned: δ- (partial negative) to the more electronegative atom and δ+ (partial positive) to the less electronegative one.

Conversions Between Units

• Use molar mass to convert between grams and moles.
• Use Avogadro's number (6.022 × 10²³) to convert between moles and particles.

Formation of a Solution

• Solvent molecules surround solute particles.
• For ionic compounds, water (a polar solvent) separates ions.
• Water's partial negative (O) attracts cations, and partial positive (H) attracts anions.

Electrolytes and Non-Electrolytes

• Dilute solutions have low solute concentration; concentrated solutions have high solute concentration.
• Electrolytes conduct electricity.
  • Strong electrolytes fully dissociate (e.g., NaCl).
  • Weak electrolytes partially dissociate (e.g., CH₃COOH).
• Non-electrolytes do not dissociate (e.g., sugar).

Dilution and Concentration Changes

• Dilution decreases concentration by adding solvent.
• Concentration increases by removing solvent (e.g., through evaporation).

Particle Diagrams for Solutions

• Depict solute (dots/ions) and solvent (molecules).
• Vary density to represent concentration.
• Include dissociated ions for electrolytes.

Dissolution of Solutes

• "Like dissolves like": Polar solvents dissolve polar solutes; nonpolar solvents dissolve nonpolar solutes.
• Dissolution depends on particle interactions (e.g., ion-dipole forces in saltwater).

Additive Volumes

• Solute and solvent volumes are additive.

Molarity and Dilution

• Molarity (M): moles of solute / liters of solution
• Dilution equation: M₁V₁ = M₂V₂

Molar Mass

• The sum of the atomic masses (from the periodic table) of all atoms in a compound.

Test your understanding of VSEPR theory and molecular geometry with this quiz. Explore the shapes of molecules based on electron repulsion, as well as the differences between intermolecular and intramolecular forces. Review examples and key concepts related to molecular polarity.