Molecular Polarity Molecular Structure Courtesy Christy Johannesson .

Molecular Polarity

Molecular Structure

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Dipole Moment

• Direction of the polar bond in a molecule.

• Arrow points toward the more electronegative atom.

H Cl+ -


Determining Molecular Polarity

• Nonpolar Molecules– Dipole moments are symmetrical and cancel

out.

BF3

F

F F

B



• Polar Molecules– Dipole moments are asymmetrical and don’t

cancel .

netdipolemoment

H2OH H

O


CHCl3

H

Cl ClCl


• Therefore, polar molecules have...– asymmetrical shape (lone pairs) or – asymmetrical atoms

netdipolemoment


Dipole Moment

Nonpolar

Polar

....

H H

O

C OO

Bond dipoles

Overall dipole moment = 0

Bond dipoles

Overall dipole moment

The overall dipole moment of a moleculeis the sum of its bond dipoles. In CO2 thebond dipoles are equal in magnitude butexactly opposite each other. The overall dipole moment is zero.

In H2O the bond dipoles are also equal inmagnitude but do not exactly oppose eachother. The molecule has a nonzero overall dipole moment.

Dipole moment,

Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 315


• Ammonia, NH3

Methane and Chloro-methane

Carbon dioxide and sulfur dioxide

......

Polar Bonds

H Cl

Polar

A molecule has a zero dipole moment because their dipoles cancel one another.

H HO

PolarF F

B

F

Nonpolar

HH

H

N

Polar

Polar Nonpolar

F FCl

F

F F

Xe

F FCl

ClC

Cl

Nonpolar Polar

Cl

HC

Cl

H

H

Molecular Polarity Molecular Structure Courtesy Christy Johannesson .

Documents

Transcript of Molecular Polarity Molecular Structure Courtesy Christy Johannesson .