Bonding/Polarity

• Molecule


  A group of two or more atoms held together by chemical bonds
• Electronegativity


  The ability of an atom to attract electrons in a bond
• Lone pair


  A pair of electrons on an atom that is not shared or bonded with another atom
• Polar bond


  A bond in which electrons are shared unequally between two atoms because one atom is more electronegative
• Nonpolar bond


  A bond where electrons are shared equally because the two atoms have the similar or same electronegativity
• Molecular geometry


  The 3d shape of a molecule, determined by the arrangement of atoms and lone pairs around the central atom
• Polarity


  Refers to the distribution of electrical charges in a molecule; polar, nonpolar
• Polar


  Has an uneven charge distribution

  Example: H2O, NH3
• Nonpolar


  Has even charge distribution

  Examples: CH4, CO2
• Bond polarity


  Arises due to differences in electronegativity between atoms. The higher the electronegativity the higher the attraction
• Molecular shape and geometry

  Valence Shell Electron Pair Repulsion

  1. Linear: nonpolar if symmetrical
  2. Bent: Polar due to asymmetry
  3. Tetrahedral: Nonpolar if symmetrical
  4. Trigonal pyramid: Polar due to asymmetry
• Dipole moment


  It measures the separation of charges in a molecule
• Dipole moment in polar molecules

  • net dipole moment ≠ 0
  • Uneven charge distribution creates partial positive and negative ends
• Dipole moment in nonpolar molecules

  • net dipole moment = 0
  • symmetrical shapes cancel out dipole