Molecular Polarity
NB: not the same as bond polarity
Definition
Molecular polarity refers to the distribution of charge on the entire molecule
- It determines many physical and even some chemical properties of a molecule
- It primarily depends on the 3-D molecular shape of the molecule, but many can be done using 2-D diagrams
Steps
Determining bond polarity:
- Check bond polarity
- Use shape to determine if the bond polarity is equal and opposite in all directions
- Note the effect of lone electron pairs
- Indicate the direction of molecular polarity using an arrow pointing to the more electronegative end
Types of Molecules
Non-polar Molecules
Info
If forces "cancel out", then there is no polarity
Examples
Polar Molecules
Info
Lone pairs cause the molecule to be polar
Examples
Weakly Polar Molecules
Info
Weakly polar molecules have lone pairs that don't cancel, but the electronegativity difference is too little (
Example