Dipole Moment, Partial Charges, and Percent Ionic Character

Dipole Moment, Partial Charges, and Percent Ionic Character 

The shift of electron density in a polar bond is symbohzed by placing a crossed arrow (a dipole arrow) above the Lewis stmctnre to indicate the direction of the shift. For example. 

A quantitative measure of the polarity of a bond is its dipole moment (fi), which is calculated as the product of the charge (Q) and the distance (r) between the charges  

For a diatomic molecule containing a polar bond to be electrically neutral, the partial positive and partial negative charges must have the same magnitude. Therefore, the Q term in Equation 8.1 refers to the magnitude of the partial charges and the calculated value of p, is always positive. Dipole moments are usually expressed in debye units (D), named for Peter Debye. In terms of more familiar SI units, 

Sample Problem 8.5 shows how to use bond lengths and dipole moments to determine the magnitude of the partial charges in a polar diatomic molecule. 

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