Polarity and Intermolecular Forces Diatomic molecules Nonpolar Polar

Polarity and Intermolecular Forces

Diatomic molecules Nonpolar Polar

Polyatomic molecules Nonpolar Polar

Bond moments and resultant dipole moments in NH 3 and NF 3.

Intramolecular forces vs Intermolecular forces Intramolecular forces- the forces which mediate interaction between molecules, including forces of attraction or repulsion which act between molecules and other types of neighboring particles, e. g. , atoms or ions. – Metallic bond – Covalent bond, Network Covalent – Ionic bond Intermolecular forces-any force that holds together the atoms making up a molecule or compound. This includes all types of chemical bonds. Inter are usually weaker than intramolecular forces. – Dispersion, aka London – Dipole-Dipole – Hydrogen bonding-strongest

London dispersion • Induced dipole • Attractive forces that arise as a result of temporary dipoles induced in atoms or molecules • Usually increase with molar mass • weakest

Dipole-dipole • Attractive forces between polar molecules

Hydrogen Bond • Forms between the hydrogen end of one dipole and the fluorine, oxygen, or nitrogen (that have at least one lone pair) end of another dipole • strongest

IMF’s • ALL molecules have dispersion forces • All polar molecules have dipole-dipole forces and dispersion forces • Molecules that H-bond have all 3

Solubility of polar molecules Properties are due to intermolecular forces Like dissolves like Polar substances will dissolve polar molecules Non polar substances will dissolve non- polar molecules v. Ionic substances will dissolve in polar molecules • •