Answer: Rhombic sulfur (alpha-sulfur).
- A Rhombic sulfur (alpha-sulfur)
- B Monoclinic sulfur according to standard textbooks
- C Plastic sulfur in general practice
- D Amorphous sulfur as frequently described
Correct answer: A. Rhombic sulfur (alpha-sulfur)
Explanation: Rhombic (alpha) sulfur is the thermodynamically stable form of sulfur at room temperature (melts at 119°C).
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.