the 90" Lp-lp angle. The Lp-lp angles are large for A and C, so the choice must come from the lp-bp and bp-bp angles. Because the Lp-bp angles are more important, C, which has only four 90" lp-bp interactions, is favored over A, which has six such interactions. Experiments have confirmed that the structure is based on C, with slight distortions due to the lone pairs. The lone pair-bonding pair repulsion causes the lp-bp angles to be larger than 90" and the bp-bp angles less than 90" (actually, 87.5"). The C1 -F bond distances show the repulsive effects as well, with the axial fluorines(approximately 90" Lp-bp angles) at 169.8 pm and the equatorial fluorine (in the plane with two lone pairs) at 159.8 pm.8 Angles involving lone pairs cannot be determined experimentally. The angles in Figure 3-12 are calculated assuming maximum syminetry consistent with the experimental shape.