Question

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`?

Answer 1

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.

Explanation:

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 `P-Cl`bond is more polar.