CHEMSITRY 11 Polarity and Intermolecular Forces Mr Krstovic

CHEMSITRY 11 Polarity and Intermolecular Forces Mr. Krstovic

Polar and nonpolar covalent bonds

• Nonpolar - EQUAL sharing of e • Polar - UNEQUAL sharing of e • Use E. N. values to predict polarity between two atoms 0 – 0. 7 nonpolar 0. 7 – 1. 7 polar 1. 7 + ionic

Guidelines for Polar Molecules • Usually any diatomic compounds (HCl, HBr, CO) • Any molecules with OH at one end (CH 3 OH) • Any molecules with O at one end (OCl 2) • Any molecule with an N at one end (NH 3)

Guidelines for Nonpolar molecules • All diatomic elements (Cl 2, N 2) • Most carbon compounds in the form of Cx. Ay

Polar or Non-polar? ? • • • CH 5 N CH 4 O C 2 H 2 Na. Cl HF CO 32 -

Intermolecular Forces • Ionic and covalent bonds are INTRAmolecular forces • INTERmolecular forces are forces between molecules

Intermolecular Forces • Ion-dipole: an attractive force between ions from ionic compoounds and polar molecules (Example: Na. Cl in Water)

• Dipole-dipole: an attractive force acting between all polar molecules (Example: between HCl molecules)

Hydrogen Bonding (A special Case of Dipole-Dipole) • A relatively strong force between a POSITIVE hydrogen atom of one molecule and a highly electronegative atom (F, O, or N) in another molecule.

• L. D. : an attractive force acting between ALL molecules, including nonpolar molecules.