NCl3, or nitrogen trichloride, is a polar molecule.
To understand why, we need to examine both the molecular geometry and the electronegativity of the atoms involved. Nitrogen (N) has an electronegativity of 3.0, while chlorine (Cl) has an electronegativity of 3.16. This difference in electronegativity creates polar covalent bonds between the nitrogen and chlorine atoms, as chlorine is more electronegative and pulls the bonding electrons closer to itself.
Furthermore, the shape of NCl3 is trigonal pyramidal due to the presence of a lone pair of electrons on the nitrogen atom. This geometric arrangement results in an uneven distribution of charge, leading to a net dipole moment. In simpler terms, because the molecule is not symmetrical, the polar bonds do not cancel out, thereby making the entire molecule polar.
In summary, the combination of polar bonds and an asymmetrical shape contributes to NCl3 being a polar molecule.