Step-by-Step VSEPR Reasoning: Why XeF4 is Square Planar

Step 1: Identify the central atom and count its valence electrons Central atom = Xe Valence electrons of Xe = 8 (Group 18, but uses 8 $e^{-}$ for bonding chemistry)

Step 2: Count bonds formed XeF4 has 4 Xe-F bonds → 4 bond pairs

Step 3: Calculate lone pairs on central atom Total electrons on Xe = 8 Used in 4 bonds = 4 Remaining = 8 - 4 = 4 electrons = 2 lone pairs

Step 4: Total electron pairs = 4 bond pairs + 2 lone pairs = 6

Step 5: Determine electron geometry 6 electron pairs → sp3d2 hybridization → Octahedral electron geometry

Step 6: Apply lone pair placement rule (for octahedral) For octahedral base: lone pairs prefer TRANS (opposite) positions to minimize repulsion. → 2 lone pairs go to the two axial positions (opposite each other, 180° apart)

Step 7: Determine molecular geometry With lone pairs in both axial positions, all 4 F atoms are in the equatorial plane. → Molecular geometry = Square Planar

Step 8: Verify bond angles F-Xe-F angle (all adjacent F atoms in the equatorial plane) = 90° Lone pair-Xe-lone pair = 180° (trans)

CONCLUSION: XeF4 is square planar because 6 electron pairs (sp3d2) arrange octahedrally, and 2 lone pairs occupy the trans axial positions, forcing 4 F atoms into a single equatorial plane.

The trap: Do NOT say tetrahedral. Tetrahedral requires 4 electron pairs with NO lone pairs (like CH4). XeF4 has 6 electron pairs (2 of which are lone pairs).