Lesson 6: Molecule Polarity

• Polarity

  The unequal sharing of electrons between atoms in a molecule
• Molecule polarity

  • Two factors must be considered: shape and presence of bond dipoles
• Greater electronegativity


  Stronger the attraction of electrons (unequal sharing)
• Electronegativity difference of the dipole

  Determines the size of the arrow
• The dipoles are in reference of the atom
• Electrons

  Repel negative charges but attract positive charges
• Atoms bonded to the central atom are identical and there are no bond dipoles means the molecule is nonpolar. Exception = All V-shaped (bent) and pyramidal-shaped molecules are polar
• Polar molecule

  Atoms bonded to the central atom are not identical and the bond dipoles may not cancel
• Nonpolar molecules

  • CH4
• Polar molecules

  • CH3F
  • CH3Cl
  • CH3Br
  • CH3I
  • They are polar because of the difference in electronegativity values
• If bond dipoles occur then vector addition can be used to determine polarity
• If vectors cancel each other out, the molecule is nonpolar; if vectors do not cancel each other out, there is a resulting molecular dipole and the molecule is polar