Lesson 12
Polar Bonds and Polar Molecules
 Based on elctronegativity we recall that EN values can be
used to calculate whether atoms have partial positive
charges or partial negative charges from the attraction of
electrons.
 Considering the shapes of the molecular compounds we
can predict whether shapes are polar or non-polar.
 Using vectors (direction of negative pull) we can predict
whether the compounds will be polar or non-polar.
 Below water is polar while carbon dioxide is non-polar.
 Symmetry often helps deciding whether molecular
compounds are polar or non-polar.
 For example, CCl4 is non-polar as all the C – Cl
bonds are identical and the four bonds cancel each
other out.
 However, CHCl3 is polar because the C – H is not the
same electronegativity as the C – Cl bond
Simple Rules for Polar vs Non-Polar
Non-Polar molecules include…
AX2, AX3, AX4 if and only if the X’s are all the same
atom. Ex: CH4, BF3, and CO2
Polar Molecules include…
 everything not listed above/everything else
 if there is an E in the general formula, it is most
certainly polar.
Homework
 Use VSEPR theory to predict the shape of each of the
following molecules. From the molecular shape and
the polarity of the bonds, determine whether the
molecule is polar and then justify your answer.
 For each of the molecules,





Draw the molecule
State general formula in terms of AXE
Name the molecular shape
State the bond angle
State whether it is polar or non-polar












CH3F
CH2O
AsI3
H2O2
BH3
CH4
SO3
HCl
PH3
H2O
SBr2
Which is more polar, NF3 or NCl3. Justify your answer.