What is molecular geometry of SCl3 ion? trigonal pyramidal trigonal bipyramidal trigonal planar T-shaped
The Correct Answer and Explanation is:
The correct answer is: T-shaped
Explanation
To determine the molecular geometry of the SCl₃⁻ ion, we apply Valence Shell Electron Pair Repulsion (VSEPR) theory, which predicts the geometry based on the repulsions between electron pairs around the central atom.
- Determine the central atom and count valence electrons:
- Sulfur (S) is the central atom.
- Sulfur has 6 valence electrons.
- Each chlorine (Cl) atom brings 7 valence electrons.
- There are 3 Cl atoms, so: 3 × 7 = 21
- One extra electron comes from the negative charge (⁻), adding 1 more.
- Total = 6 (S) + 21 (Cl) + 1 (extra) = 28 valence electrons
- Assign electrons:
- 3 S–Cl bonds = 3 × 2 = 6 electrons
- Remaining = 28 − 6 = 22 electrons
- Distribute remaining electrons as lone pairs on Cl atoms first (each needs 6 more to complete octet): 3 × 6 = 18
- Remaining electrons = 22 − 18 = 4 electrons, which are placed as 2 lone pairs on the central S atom.
- Determine electron regions:
- 3 bonding pairs (from 3 S–Cl bonds)
- 2 lone pairs (on S)
- This gives a total of 5 electron domains → This corresponds to a trigonal bipyramidal electron geometry.
- Determine molecular geometry:
- In a trigonal bipyramidal geometry, lone pairs occupy equatorial positions to minimize repulsion.
- The three Cl atoms will occupy two axial and one equatorial positions.
- This results in a T-shaped molecular geometry (3 atoms, 2 lone pairs).
Thus, the molecular geometry of SCl₃⁻ is T-shaped, not trigonal pyramidal, bipyramidal, or planar.
