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I don't quite understand this part in the explanation below "molecular dipole are only...

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mattlimey | Student, Grade 11 | Honors

Posted July 2, 2013 at 2:22 AM via web

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I don't quite understand this part in the explanation below "molecular dipole are only a fraction of the size of the charges on an ion"

How Polar Bonds create Inter-molecular Forces:

The charges on each end of a molecular dipole are only a fraction of the size of the charges on an ion, but they do cause electrical forces to occure between nearby molecules.

 

Can you please give an easier explanation?

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ncchemist | eNotes Employee

Posted July 2, 2013 at 3:05 AM (Answer #1)

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Think of this in terms of magnitude or size.  A true ion is something like the sodium cation (Na+) or the chloride anion (Cl-).  There is a full charge on the ion that is a whole integer value (1, 2, 3, etc.).  A molecular dipole is not a full charge on an atom like you find in an ion.  A dipole is a partial charge.  If two atoms covalently bonded together experience a dipole, that means that one of the atoms will have a partial positive charge and the other atom will have a partial negative charge.  This is because the electron density in the bond is shifted toward the the more electronegative atom.  But the important point here is that a dipole is merely a partial charge, whereas an ion is a full charge.  This is why they use the phrase "molecular dipole are only a fraction of the size of the charges on an ion."

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