Phosphorus trifluoride, or PF3, is a polar molecule. It contains three nonpolar bonds arranged asymmetrically around the central phosphorus atom, thus conferring a net dipole moment on the molecule.
Phosphorus has five valence electrons, three of which are shared with the three fluorine atoms in PF3. The remaining two non-bonded electrons remain as a lone pair. The lone pair of electrons repels the electrons in the three covalent bonds formed between phosphorus and fluorine to give the molecule a trigonal pyramidal shape, where the fluorine atoms form the base of the pyramid.
Fluorine has a higher electronegativity than phosphorus and attracts the bonded electron pair towards itself, thus obtaining a partial negative charge. This gives phosphorus a partial positive charge, and the entire molecule a net dipole moment. The individual bond polarities do not cancel each other out because of the geometric arrangement of the bonds, making PF3 a polar molecule.