To determine the polarity of a covalent bond, you need to look at the electronegativity of the atoms involved. Electronegativity is a measure of an atom's ability to attract electrons. The greater the difference in electronegativity between two atoms, the more polar the bond between them will be.

In PCI3, the electronegativity of phosphorus is 2.19, while the electronegativity of chlorine is 3.00. This means that there is a significant difference in electronegativity between phosphorus and chlorine, which results in a polar covalent bond.

The polar covalent bond between phosphorus and chlorine creates a partial positive charge on the phosphorus atom and a partial negative charge on the chlorine atom. This polarity allows PCI3 to interact with other polar molecules and ions, making it a versatile compound with a wide range of applications.