Chem 3i Intermolecular Forces

KE keeps particles…. Attractive Forces….

1. apart

2. together

Inter vs Intra

Inter is weaker than intra

Properties that reflect intermolecular forces :

Boiling points, melting points, viscosity, surface tension and capillary action

Intra force examples

Ionic, metallic, covalent bonds

Inter force examples

Dispersion, Dipole-Dipole, and Hydrogen Bonding

SOMETIMES order weakest to strongest Forces

Dispersion, dipole dipôle, hydrogen bonding

What is Dispersion Forces ?

Any molecule (polar or non) is tenporarioly polarized. Easier polarized, the stronger the forces.

Polarized Definition

Tendancy of electron cloud to distort

Factors that increase Dispersion forces

More electrons, Less compact shape/more SA,

Dipole - Dipole Interactions

POLAR ONLY - negative and positive ends (opposites attract)

If molecules are same size and shape, Dipole dominates

Increasing Boiling Point Factors

if same sizes and shape, polar = increases BP

Strong IMF

Easy to polarize

More SA/More Attraction

Hydrogen Bonding

Polar molecules with electronegative Nitrogen, Oxygen, and Fluorine (creates dipole dipole but extra strong)

Ion Dipole

Ionic solids dissolved in polar liquids