The shape of the sulphur hexafluoride molecule, SF6, is

  • A. tetrahedral
  • B. octahedral
  • C. trigonal bipyramidal
  • D. square planar

Explanation

Six bond pairs around the central sulphur arrange themselves at 90 degrees to one another at the corners of an octahedron. This requires sulphur to expand its octet using d orbitals, which is possible from period 3 onwards but never for carbon, nitrogen or oxygen. Phosphorus pentachloride, with five pairs, is trigonal bipyramidal by the same reasoning.

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