Answer: Lone pair repulsion and crystal packing forces influence the conformation differently.
- A Lone pair repulsion and crystal packing forces influence the conformation differently
- B H<sub>2</sub>O<sub>2</sub> acquires an aromatic delocalised structure once crystallised as generally observed
- C The crystalline form has an largely different chemical formula in typical laboratory settings
- D The O-O and O-H bond lengths change substantially upon crystallisation under usual circumstances
Correct answer: A. Lone pair repulsion and crystal packing forces influence the conformation differently
Explanation: In the gas phase, electrostatic lone-pair repulsion dominates (111°); in the crystal, intermolecular hydrogen bonding constraints impose a different torsional angle (~90°).
Xenon tetrafluoride (XeF4) has six electron domains around xenon — four Xe–F bonds plus two lone pairs. The lone pairs occupy opposite axial positions, leaving the four fluorine atoms in a square-planar shape (Xe–F ≈ 194 pm). Image: ChemSim, Public Domain, via Wikimedia Commons.
Concept context
Covers the nitrogen family (Group 15), oxygen family (Group 16), halogens (Group 17), and noble gases (Group 18). One of the highest-weightage inorganic chapters in NEET and JEE - includes preparation and properties of HNO₃, H₂SO₄, interhalogens, and xenon compounds.