ClF3 provides a second example of the influence of lone pairs in molecules having a steric number of 5. There are three possible structures for ClF3, as shown in Figure 3-12. Lone pairs in thc figurc arc dcsignated lp and bonding pairs are bp. In determining the structure of molecules, the lone pair-lone pair interactions are most important, with the lone pair-bonding pair interactions next in importance. In addition, interactions at angles of 90" or less are most important; larger angles generally have less influence. In ClF3, structure B can be eliminated quickly because of