PCl3 (Phosphorus Trichloride) is a polar molecule. The polarity of PCl3 arises due to its molecular geometry and the difference in electronegativity between phosphorus and chlorine atoms.
Phosphorus has an electronegativity of 2.19, while chlorine has an electronegativity of 3.16. This difference in electronegativity causes the P-Cl bonds to be polar, with chlorine atoms pulling the shared electrons more strongly than phosphorus.
Additionally, PCl3 has a trigonal pyramidal molecular geometry. The lone pair of electrons on the phosphorus atom creates an uneven distribution of electron density, leading to a net dipole moment. This means that the molecule has a positive end (phosphorus) and a negative end (chlorine atoms), making PCl3 a polar molecule.