Intermolecular Forces

Polarity depends on..

The bonds and the shape of the molecule

Polar:

Electrons are distributed evenly, one end partially positive, and one end partially negative

Non polar:

molecule has no overall seperation of positive and negative charges

what are the steps when determining weather its polar or non polar?

1. Are there polar bonds? Do bonded atoms have different electronegativities

2. What is the molecular shape?

3. Do the bond dipoles cancle?

If dipoles cancel that means its??

Non polar

If dipoles do not cancel?

polar

Molecular Geometry:

Linear-

Non-polar: idential atoms on each side, meaning dipoles cancel.

Molecular Geometry:

Bent-

Polar: dipoles do not cancle

Molecular Geometry:

Tetrahedral-

Nonpolar: symmetrical, identical outer atoms

Molecular Geometry:

Trigonal Pyramidal-

Polar, dipoles do not cancle

Molecular Geometry:

trigonal planar:

Non polar

What forces occur when non polar

London Dispersion only

What forces occur when polar

London dispersion, dipole-dipole, and if H is bonded to O,N,or F, add hydrogen bonding

Ion dipole-

being disolved in water to create an ion and a polar moment

Boiling Point:

stronger intermolecular forces= higher boiling point

Boiling Point:

Hydrogen bonding:

often raises BP significantly

Boiling Point:

Dipole- Dipole:

Polar molecules attract eachother

Boiling Point:

Molecular size/shape:

more electrons= stronger LDF forces

Boiling Point:

Comparing shape if necesarry

long less branched= stronger dispersion