In: Chemistry
(b) Which have a molecular dipole moment? (Select all that apply.)
CF4
BF3
PF3
OF2
F2
PF3 and OF2 have Dipolemoment
Rest of the structures are having symmetry. Hence net dipole moment of the molecules are zero.
Dipole moments arise out of an asymmetry in the electronegativity between atoms.
OF2
The dipole moments of the molecules are related to the geometry of the molecules. Consideration of the Lewis structure shows that OF2 assumes an angular configuration which have 2 bonded atoms and 2 non-bonded electron pairs around the central oxygen atom. which make the molecule unsymmetry and it has net dipolemoment.
PF3
In PF3, Fluorines are more electronegative than phosphorous. The phosphorous is at the apex of a pyramid, the base of the pyramid being an equilateral triangle with a fluorine atom at each vertex. Each F-P bond contributes to the net dipole moment, as a vector from the P to the F. The net dipole moment is the vector sum of the vectors along the three P-F bonds. If all four atoms were in a plane (a trigonal planar geometry), there would be no net dipole moment. But because the geometry is pyramidal, the vector sum is not zero and there is a net dipole moment.