Examkin

Question

Difficulty: HardMolecular Shapes, VSEPR Theory, and Hybridization

The sulfite ion (SO32−SO_3^{2-}) is formed when sulfur dioxide dissolves in aqueous basic media. Based on Valence Shell Electron Pair Repulsion (VSEPR) theory, which of the following correctly describes the hybridization of the central sulfur atom and the molecular geometry of the SO32−SO_3^{2-} ion?

  1. sp3sp^3 hybridization with trigonal pyramidal molecular geometryAnswer
  2. B
    sp3sp^3 hybridization with tetrahedral molecular geometry
  3. C
    sp2sp^2 hybridization with trigonal planar molecular geometry
  4. D
    sp2sp^2 hybridization with bent molecular geometry

Answer

The central sulfur atom in the sulfite ion (SO32−SO_3^{2-}) exhibits sp3sp^3 hybridization and has a trigonal pyramidal molecular geometry.
The central sulfur atom in SO32−SO_3^{2-} possesses 4 electron domains (3 bonding pairs and 1 non-bonding lone pair), yielding sp3sp^3 hybridization. According to VSEPR theory, an AX3EAX_3E electron arrangement produces a trigonal pyramidal molecular shape.

Step-by-Step Solution

1
Determine total valence electrons for SO32−SO_3^{2-}
Sulfur provides 6, each of the three oxygens provides 6, plus 2 electrons from the 2−2- charge: 6+(3×6)+2=266 + (3 \times 6) + 2 = 26 valence electrons (13 pairs).
Accurate valence electron counting is necessary to determine bonding and non-bonding electron distribution.
2
Determine electron domain count and steric number on the central atom
Sulfur forms 3 single sigma bonds to oxygen atoms and retains 1 lone pair of non-bonding electrons (3 bonding pairs+1 lone pair=4 total electron domains3 \text{ bonding pairs} + 1 \text{ lone pair} = 4 \text{ total electron domains}).
Steric number determines the orbital hybridization of the central atom.
3
Determine hybridization and molecular geometry using VSEPR theory
A steric number of 4 corresponds to sp3sp^3 hybridization. With 3 bonding pairs and 1 lone pair (an AX3EAX_3E system), the electron geometry is tetrahedral, but the actual molecular geometry is trigonal pyramidal.
Molecular geometry is named based only on the spatial arrangement of the bonded atoms, not the non-bonding lone pair.

Key Concept

VSEPR theory and hybridization determination for polyatomic ions with lone pairs
Estimated Time:1m 30s
Rate this question

Topics

Molecular Shapes, VSEPR Theory, and Hybridization

More questions from this topic