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### Clarification of what a Dipole Moment is

Posted: Mon Oct 27, 2014 6:32 pm
I need some clarification on what a Dipole Moment is. I understand that it is the measure of a charge difference, but how exactly does this connect to covalent bonds and how do we calculate or find it?

### Re: Clarification of what a Dipole Moment is

Posted: Mon Oct 27, 2014 8:54 pm
It is a measure of the charge separation. The dipole moment of a hydrogen-carbon bond will be much smaller than the dipole moment of a hydrogen-oxygen bond because in the hydrogen-oxygen bond the charge is separated more due to the electronegativity difference. In terms of covalent bonds the dipole moment quantifies the charge distribution on the molecule. That is, where the electrons are most of the time.

To actually calculate a value for the dipole moment you would need to know how the elctronegativity af the two heteroatoms affect the charge separation.

The dipole moment tells you about the polarity of the bond and the net dipole of the molecule tells you if it is polar or not.

### Re: Clarification of what a Dipole Moment is

Posted: Mon Oct 27, 2014 9:01 pm
Krista Lum 3a

Dipole moments arise from differences in electronegativity (so in nearly all molecules except diatomic molecules between two atoms of the same element--N2, H2, O2...etc.). When one atom has a stronger pull for electrons, partial charges are created. One atom might have a partial positive and another atom might have a partial negative, and they will attract each other electrostatically.

Covalent bonds (except for diatomic molecules between two atoms of the same element--N2, H2, O2, etc) will also have partial charges because there is a difference in electronegativity. This means there will be dipole moments, moments where the positve and negative ends line up and electrostatically attract because of the difference in pull. Thus, covalent bonds will have dipole moments.

To calculate it,
$\mu =qr$

where mu is the dipole moment
q is the magnitude of the charge (absolute value of it)
and r is the distance between the charges