Valence Shell Electron Repulsion Theory (VSEPR)

Intermolecular forces Intramolecular forces Chemical Bonding Intermolecular forces Intramolecular forces

Polarity Polar bonds are a result of varying electronegativities

Polar vs. Non-Polar If the polar bonds of a molecule are oriented such that they are in opposite directions, the dipoles are cancelled out and the molecule is non-polar Example CH4

Polar vs. Non-Polar If the polar bonds of a molecule are oriented such that they complement each other, then the molecule is polar Eg. Water

General Rule Molecule will be polar if it has polar covalent bonds and there are one lone pair of electrons on the central atom.

Intramolecular Forces Force between atoms in the molecules Strong bonds Eg. Covalent bond

Intermolecular Forces Force holding molecules next to other molecules Weak forces Also called Van der Waals forces

2 Types of Van der Waals Forces dipole-dipole force London force

Dipoles Polar molecules are often referred to as dipoles (slightly positive and negative ends). Polar molecules experience an attraction between molecules. These are called dipole-dipole forces

Hydrogen Bonding Special type of dipole-dipole forces Hydrogen bonding is particular strong dipole-dipole force

London Forces The weakest of van der Waals forces and are the result of momentary dipoles. Eg. He

London Forces In general, the more electrons an atom/molecule has, the stronger the London forces. The greater the atomic number of an atom, the stronger the London force.

London Forces ALWAYS PRESENT A lot weaker than covalent or ionic bonds. Hence, London forces are important when they are the only force of attraction between 2 species.

London Forces Important between the following closed-shell species: Adjacent noble gas atoms Adjacent covalently-bonded molecules (made up of atoms having a full shell after bonding)