(a) There is a small difference in electronegativity between C and N, represented as a short vector. The length of the arrow is proportional to the magnitude of the electronegativity difference between the two atoms. A small plus sign is drawn on the less electronegative end to indicate the partially positive end of the bond. Dipole vectors are shown as arrows pointing along the bond from the less electronegative atom toward the more electronegative atom. This bond moment can be represented as a vector, a quantity having both direction and magnitude ( Figure 1). The magnitude of a bond dipole moment is represented by the Greek letter mu ( µ) and is given by the formula shown here, where Q is the magnitude of the partial charges (determined by the electronegativity difference) and r is the distance between the charges: This separation of charge gives rise to a bond dipole moment. | Key Concepts and Summary | Glossary | End of Section Exercises | Molecular Polarity and Dipole MomentĪs discussed previously, polar covalent bonds connect two atoms with differing electronegativities, leaving one atom with a partial positive charge (δ +) and the other atom with a partial negative charge (δ –), as the electrons are pulled toward the more electronegative atom. | Molecule Polarity and Dipole Moment | Properties of Polar Molecules | Predict molecular polarity and molecular dipole moments by considering molecular shape and bond polarity.
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