The shape/structure of [XeF5]- and XeO3F2, respectively are:

🧠 Use the steric number method for each xenon species. Xe has 8 valence electrons; account for the ionic charge when counting.

$\ce{[XeF5]-}$: Xe valence e = 8; charge −1 adds 1e → 9e on Xe. 5 bonds use 5e from Xe, leaving 4e = 2 lone pairs. Steric number = 5 + 2 = 7 → pentagonal bipyramidal electron geometry. The 2 LP take axial positions → pentagonal planar molecular shape.

$\ce{XeO3F2}$: Xe bonds to 3 O (double bonds, but count as 1 σ-bond group each) + 2 F = 5 bond groups. Remaining Xe valence electrons: 8 − 5 = 3e... effectively 0 lone pairs in the σ-framework. Steric number = 5 + 0 = 5 → trigonal bipyramidal.

⚠️ Trap: Option (b) proposes "octahedral" for $\ce{[XeF5]-}$ — octahedral requires 6 bond groups, not 5. With 7 electron groups and 2 LP, the molecular shape is pentagonal planar, not octahedral.

$\boxed{\text{Answer: (a) Pentagonal planar and trigonal bipyramidal}}$