Bond Polarity & Molecular Polarity

 Occur when there is equal sharing of electrons between two atoms.  Form between:  Two identical nonmetal atoms.  Two nonmetals with electronegativity difference of 0.3 or less.  Atoms have balanced distribution of electrical charge. Nonpolar Covalent Animation

 Occur when there is unequal sharing of electrons between two atoms.  Form between two different nonmetals that have electronegativity difference between 0.3 and 1.7.  One atom will have a partial positive charge, the other will have a partial negative charge. Polar Covalent Animation

 Created by the unequal distribution of electrons in polar covalent bonds.  Electronegativity is a measure of how much an atom “hogs” electrons in a bond.  Electrons spend more time around the more electronegative atom.  Atom has a partial negative charge.  Electrons spend less time around the less electronegative atom.  Atom has a partial positive charge.

 Determined by using chart below:

 Dipoles are symbolized by:  The arrow end is placed near the partially negative atom (the more electronegative atom).  The tail end is placed near the partially positive atom (the less electronegative atom).  Electronegativity difference is used to determine if arrow is drawn or not:  Difference of 0.3 or less = NO ARROW.  Difference above 0.3 but less than 1.7 = ARROW.

 HCl  IBr  No bond dipole because electronegativity difference is less than 0.3. N2N2  CO

 A molecule will be polar if:  1. It has bond dipoles.  2. The bond dipoles are unequally distributed.  Draw dipoles on the molecules below and determine if they are polar or nonpolar.

 Answers:  Water is polar.  Ammonia is polar.  Carbon tetrachloride is nonpolar.  Carbon dioxide is nonpolar.