Final answer:
Of the species listed, only BCl₃ will have bond angles of 120° because it has a trigonal planar electron-pair geometry and molecular structure with no lone pairs on the central atom.
Step-by-step explanation:
Of the following species, BCl₃ will have bond angles of 120°. This is because BCl₃ has a trigonal planar electron-pair geometry and a trigonal planar molecular structure. Since there are no lone pairs of electrons on the central boron atom, the three regions of high electron density (from the B-Cl bonds) will spread out equally in a plane around the central atom, resulting in bond angles of exactly 120°.
Looking at the other molecules: PH₃ has a tetrahedral electron-pair geometry and a trigonal pyramidal molecular structure; ClF₃ has a trigonal bipyramidal electron-pair geometry and a T-shaped molecular structure; NCl₃ also has a tetrahedral electron-pair geometry and a trigonal pyramidal molecular structure. Therefore, none of these molecules will have bond angles of 120° due to the presence of lone pairs and different electron-pair geometries.