A molecule with the formula AX4Y has all its elements from p-block. Element A is rarest, monoatomic, non-radioactive…

🧠 Identify elements A, X, Y from the clues, then determine the molecular geometry of AX₄Y.

🗺️ Step 1 — Identify X and Y:

• X has the highest electronegativity among all elements → F (EN = 3.98)
• Y has the second highest electronegativity → O (EN = 3.44)

Step 2 — Identify A:

A is from p-block, rarest in its group, monoatomic (noble gas), non-radioactive, and has the lowest IE among A, F, O:

• Rarest non-radioactive noble gas: Xe (Z = 54)
• IE of Xe ≈ 1170 kJ/mol; IE of F ≈ 1681; IE of O ≈ 1314 → Xe has lowest IE ✓

Step 3 — Molecule is $\mathrm{XeF_4O}$ → $\mathrm{XeOF_4}$

Xe has: 4 Xe–F bonds + 1 Xe=O bond + 1 lone pair on Xe Steric number = 4 + 1 + 1 = 6 → sp³d² hybridization

Electron geometry: octahedral The lone pair occupies an equatorial-like position (or axial) → lone pair + 1 oxygen (double bond) + 4 F (single bonds) → square pyramidal geometry (Xe at center, 4 F at base, O at apex)

$\boxed{\text{Answer: Square pyramidal}}$