How many lone-pairs of electrons (first) and bonding pairs of electrons exist on

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Using VSEPR, the geometry of the molecule is trigonal bipyramidal. This means that there are three different possible locations of the lone pairs; both in the axial positions, both in the equatorial, or one in each. You need to keep the lone pairs (lp) as far away from each other, whilst minimizing the lone pair-bond pair (lpbp) repulsion. Repulsions greater than (or equal to) 120 degrees can be ignored. lplp > lpbp > bpbp If the two lone pairs were both in the equatorial, you'd have no lplp repulsion (since the angle between them is = 120 deg. 4 lpbp interactions (2 from the above F atom with the lone pairs and 2 from the below F atom) and 2 bpbp repulsions (from the other F atom with the 2 axial F atoms) If the lone pairs were on the axis, then you'd have 6 lpbp interactions (3 F atoms with both lone pairs) If it were one each, then you'd have 1 lplp, 3 lpbp and 2 bpbp interactions.

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