The molecule having smallest bond angle is

NPAsSb Group=15 Valenceelectrons=5MCl3 has  sp3 hybridized M-element with one lone-pair.Lone pair and bond pair repulsion decreases bond angle. However, the bond-pairs of electrons are much farther away from the central atom than they are in NCl3. Thus, lone-pair causes even greater distortion in PCl3,  AsCl3 and  SbCl3. Thus, bond angle decreases from NCl3 (maximum) to SbCl3 (minimum).