Give the number of lone pair electrons around the central atom and identify the molecular geometry of sulfur dichloride, Sci2. Hint:
a) Zero Lone Pairs; Linear
b) One Lone Pair; Bent
c) Two Lone Pairs; Bent
d) Three Lone Pairs; Bent
e) Three Lone Pairs; Linear
The correct answer and explanation is :
The correct answer is: c) Two Lone Pairs; Bent
Explanation (≈300 words):
Sulfur dichloride (SCl₂) is a covalent compound consisting of one sulfur (S) atom as the central atom bonded to two chlorine (Cl) atoms. To determine the number of lone pair electrons on the sulfur atom and the molecular geometry, we need to examine the Lewis structure and apply the VSEPR theory (Valence Shell Electron Pair Repulsion).
Step 1: Count Valence Electrons
- Sulfur (Group 16) has 6 valence electrons.
- Each chlorine (Group 17) has 7 valence electrons.
- Total = 6 (S) + 2×7 (Cl) = 20 valence electrons
Step 2: Draw the Lewis Structure
- Place S in the center with two single bonds to each Cl atom.
- Each S–Cl bond uses 2 electrons × 2 = 4 electrons.
- Distribute the remaining 16 electrons to complete octets for Cl atoms first (6 electrons on each).
- After satisfying Cl, 4 electrons remain, which are placed as 2 lone pairs on sulfur.
So, sulfur has two bonding pairs (S–Cl) and two lone pairs.
Step 3: Apply VSEPR Theory
- The total number of electron domains (regions of electron density) around sulfur = 2 bonding pairs + 2 lone pairs = 4 electron domains.
- According to VSEPR, four electron domains arrange themselves in a tetrahedral electron geometry to minimize repulsion.
- However, only two of those are bonding pairs, which determines the molecular shape (not the electron geometry).
- The molecular shape with 2 bonding pairs and 2 lone pairs is bent.
Step 4: Determine Molecular Geometry and Lone Pairs
- Lone pairs on central atom (S): 2
- Molecular Geometry: Bent
This is similar to the geometry of water (H₂O), which also has 2 bonding pairs and 2 lone pairs.
Final Answer:
(c) Two Lone Pairs; Bent