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JEE Advanced 2019 Paper 2 · Chemistry · Chemical Bonding and Molecular Structure · easy

The correct statement(s) about the shapes and bonding of molecules and ions is(are)

One or more options correct

The correct statement(s) about the shapes and bonding of molecules and ions is(are)
  1. A. In SF4\mathrm{SF_4} the lone pair occupies an axial position of the trigonal bipyramid, giving a see-saw shape
  2. B. I3−\mathrm{I_3^-} is linear, with three lone pairs on the central iodine atom
  3. C. XeO3\mathrm{XeO_3} is a planar triangular molecule with sp2sp^2 hybridised xenon
  4. D. BrF5\mathrm{BrF_5} has a trigonal bipyramidal molecular geometry
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Answer: B

Use VSEPR with lone pairs placed equatorially in a trigonal bipyramid. SF4\mathrm{SF_4} has 4 bond pairs and 1 lone pair; the lone pair sits in an equatorial position (fewer 90 degree repulsions), giving the see-saw shape, so (A) is wrong because of the axial claim. In I3−\mathrm{I_3^-} the central iodine has 2 bond pairs and 3 lone pairs, sp3dsp^3d, and the three lone pairs occupy the equatorial plane, leaving the three atoms linear; (B) is correct. XeO3\mathrm{XeO_3} has 3 bond pairs and 1 lone pair on xenon, sp3sp^3, so the molecule is trigonal pyramidal, not planar; (C) is wrong. BrF5\mathrm{BrF_5} has 5 bond pairs and 1 lone pair (octahedral electron geometry), so the molecular geometry is square pyramidal; (D) is wrong.
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