5Covalent bond between same atoms Covalent bond between atoms of the sameelement is nonpolar→ nonpolar molecule.Bonding electrons are shared equally.Example:
6Covalent bond between different atoms is polar.- bonding electrons closer to the moreelectronegative atom.However, molecules could be polar ornonpolar, depending on its shape.
7Determining polar and nonpolar molecules Use the three-step approach outlined below :Use electronegativity values to predict bonddipoles.Use the VSEPR method to predict the molecular shape.From the molecular shape, determine whether bond dipoles cancel to give a non-polar molecule or combine to produce a (resultant dipole moment) for the molecule.
8Molecules with different atoms & asymmetrically arranged are polar. Example:
9Molecules with different atoms, symmetrically arranged but having µ = 0 are nonpolar.Example:In CCl4, each bond is polar.The molecule as a whole, however, is nonpolar
10Example:In SF6, each bond is polar.The molecule is nonpolar
11Molecules with different atoms, symmetrically arranged but having µ ≠ 0 are polar.Example:The molecule is polar because µ ≠ 0 .The dipole moment arises because the differencein electronegativity.
12Cl C H H H Chloromethane ( CH3Cl) Example: The molecule is polar because µ ≠ 0 .The dipole moment arises because the differencein electronegativity.
13Molecules with lone pairs on the central atom Let us consider the molecules in which there are lone pairs on the central atoms.Note: Molecules which have lonepairs are usually polar.
14Ammonia ( effect of lone pairs ) Example: 0
16Which of the following molecules have a dipole moment?H2O, CO2, SO2, and CH4SOOHHdipole momentpolar moleculedipole momentpolar moleculeCHCOno dipole momentnonpolar moleculeno dipole momentnonpolar molecule
17Exercise 1Indicate the direction in which the shared electron pair is shifted in the molecules givenbelow.