3.3 Polar bonds and Polar Molecules

Polar Bonds Polar covalent bonds have 0 < ∆En < 1.7 ∆En = 0Pure covalent 0 < ∆En < 0.4Slightly polar 0.5 < ∆En < 1.7Polar covalent ∆En ≥ 1.7Ionic Electrons are more dense around the atom with higher electronegativity

Molecular Polarity An entire molecule may be polar There must be a positive end and a negative end Polar molecules have special properties

Polar Liquids Polar liquids will bend towards a charged object The molecules arrange themselves so that the oppositely charged end is close to the charged object

Non-Polar Molecules Even with polar bonds, a molecule may still be non-polar The positive and negative charges may cancel out The charges are often cancelled out in symmetrical molecules

Determining the pOlarity of a Molecule 1.Draw the Lewis Structure for the molecule. 2.Determine the ∆En for each bond. 3.If there are polar bonds, indicate the partial charges (with  + and -  ) 4.Examine the shape to see if the molecule is polar.

Homework Read pages 102 – 108 Page 107 # 1 Page 108 # 1, 2, 4, 5