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Difficulty: MediumMolecular Shapes, VSEPR Theory, and Hybridization

What are the molecular shape and the hybridization state of the central atom in a molecule of xenon trioxide (XeO3XeO_3)?

  1. Trigonal pyramidal shape with sp3sp^3 hybridizationAnswer
  2. B
    Trigonal planar shape with sp2sp^2 hybridization
  3. C
    Tetrahedral shape with sp3sp^3 hybridization
  4. D
    T-shaped shape with sp3dsp^3d hybridization

Answer

Trigonal pyramidal shape with sp3sp^3 hybridization
In xenon trioxide (XeO3XeO_3), the central xenon atom possesses 8 valence electrons. It forms 3 double bonds with oxygen atoms (using 6 electrons for bonding) and retains 1 non-bonding lone pair. The steric number is 4 (3 σ\sigma-bonds + 1 lone pair), which directs the hybridisation state to sp3sp^3. While the four electron domains adopt a tetrahedral spatial distribution, the presence of one lone pair results in a trigonal pyramidal molecular geometry.

Step-by-Step Solution

1
Determine the valence electron count of the central atom and total electron domains.
Xenon (Group 18) has 8 valence electrons. It forms three double bonds with oxygen atoms (utilizing 6 valence electrons), leaving 2 unshared electrons (1 lone pair).
VSEPR theory requires calculating the total number of electron domains (σ\sigma-bonds + lone pairs) on the central atom.
2
Calculate the steric number and determine the hybridization state.
Steric number = 3 σ\sigma-bonds + 1 lone pair = 4 electron domains, which corresponds to sp3sp^3 hybridization.
Four electron domains arrange in a tetrahedral arrangement requiring four sp3sp^3 hybrid orbitals.
3
Deduce the molecular shape from the electron domain geometry.
With 4 electron domains (3 bonding, 1 non-bonding), the electron geometry is tetrahedral while the molecular shape (atomic arrangement) is trigonal pyramidal.
Molecular shape describes only the arrangement of atomic nuclei around the central atom, excluding lone pairs.

Key Concept

VSEPR Theory, Steric Number, and Hybridization
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Topics

Molecular Shapes, VSEPR Theory, and Hybridization

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