Interhalogens form between two different halogens with the larger, less electronegative halogen as the central atom. Types: XX' (ClF, BrF, ICl), XX'3 (ClF3, BrF3, ICl3), XX'5 (BrF5, IF5), XX'7 (IF7). Geometries follow VSEPR: ClF3 has SN = 5 (3 bp + 2 lp), sp3d, T-shaped. BrF5 has SN = 6 (5 bp + 1 lp), sp3d2, square pyramidal. IF7 has SN = 7 (7 bp + 0 lp), sp3d3, pentagonal bipyramidal. All interhalogen compounds are more reactive than their constituent halogens. They act as strong fluorinating agents. ICl is used as a reagent in iodometry. The bond in an interhalogen is weaker than in the corresponding homonuclear diatomic because of size mismatch.