In terms of a #P-Cl# bond in a molecule of #PCl_5#, why it is more polar than a #P-S# electron bond in a molecule of #P_2S_5#?
The polarity of a bond depends on both atoms involved in the bond. The difference an this case is due to the difference in electronegativity between chlorine and sulfur.
As mentioned above, one must consider the difference in the electronegativities of the two bonded atoms. Chlorine is somewhat more electronegative than sulfur.
Since electronegativity is designed to provide a measure of an atom's ability to draw bonding electrons toward itself, a bond having a greater difference between the atoms will be one in which the sharing of electrons is more unequal, and a greater bond dipole results.
Thus, chlorine is better able to draw electrons away from phosphorus than is sulfur, and the