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GATE 2022 CY – Question 22

Physical Chemistry · Group Theory: Symmetry elements and symmetry operations. Basic postulates of groups and group multiplication tables. Classes, reducible and irreducible representations of symmetry elements. Classification and labelling of molecular point groups. Symmetry based selection rules and their application to electronic and vibrational spectroscopy. Internal coordinates and symmetry labelling of vibrational modes; symmetry adapted linear combination of atomic orbitals (LCAO-MO); construction of hybrid orbitals using molecular point group symmetry. · 1 mark · Multiple choice

The point group of $SF_6$ is ______.

  1. $D_{6h}$
  2. $O_h$
  3. $D_{6d}$
  4. $C_{6v}$

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Correct answer: (B) $O_h$

Explanation

Six equivalent fluorines occupy the vertices of a regular octahedron around sulfur. The molecule has octahedral rotations, inversion and mirror operations, giving **Oh, B**. A sixfold-axis group would describe a hexagonal arrangement, not this octahedron.