CHEM

• Molecular geometry


  The three-dimensional arrangement of atoms in a molecule
• Polarity of molecules


  Can be determined by looking at the geometric shape and arrangement of electrons
• Determining if a molecule is polar or nonpolar

  1. Look at the structure of the molecule

  2. Consider the number of electron pairs around the central atom

  3. Determine the molecular geometry
• Lewis electron dot structure


  Represents the valence electrons of an element using dots placed around the chemical symbol
• Lewis dot structures


  • Oxygen
  • Chlorine
  • Hydrogen
• Valence electrons


  The electrons in the outermost shell of an atom that participate in chemical bonding
• Families in the periodic table

  • Family 1A (1 valence electron)
  • Family 2A (2 valence electrons)
  • Family 3A (3 valence electrons)
  • Family 4A (4 valence electrons)
  • Family 5A, 6A, 7A
• Lewis dot structures


  • Water (H2O)
  • Ammonia (NH3)
• Bond pairs


  Shared electron pairs that form chemical bonds
• Lone pairs


  Unshared electron pairs that do not participate in bonding
• Molecular geometries


  • Linear
  • Trigonal planar
  • Bent
  • Tetrahedral
  • Trigonal pyramidal
  • Trigonal bipyramidal
  • Octahedral
• Predicting the shape of a molecule

  1. Count the number of electron pairs around the central atom

  2. Determine the molecular geometry based on the number of bond pairs and lone pairs
• Nonpolar molecule


  Symmetrical shape, equal sharing of electrons, no dipole moment
• Polar molecule


  Asymmetrical shape, unequal sharing of electrons, dipole moment
• Polar molecules


  • Hydrogen chloride
  • Water
  • Ammonia
• Molecular geometry


  Affects the physical and chemical properties of molecules and their reactivity