What is the geometry of SO2 (include the steps for deciding the geometry)?
The correct answer and explanation is :
The geometry of sulfur dioxide (SO₂) is bent or V-shaped. Here’s how this conclusion is reached step-by-step:
Step 1: Determine the Lewis Structure
The first step in determining the geometry of SO₂ is to draw its Lewis structure. Sulfur dioxide consists of a sulfur atom (S) and two oxygen atoms (O). Sulfur, being in Group 16, has 6 valence electrons, and each oxygen atom, also in Group 16, has 6 valence electrons. The total number of valence electrons is:
- Sulfur: 6 electrons
- Oxygen (2 atoms): 6 × 2 = 12 electrons
- Total = 6 + 12 = 18 valence electrons
To satisfy the octet rule, sulfur forms a double bond with each oxygen atom, sharing four electrons with each. This leaves no lone electrons on the sulfur atom, but each oxygen gets two lone pairs. The final structure shows sulfur in the center with two double bonds, one to each oxygen atom.
Step 2: Count the Electron Pairs Around the Central Atom
Sulfur in SO₂ is surrounded by two bonding pairs (each from a double bond to oxygen), and there are no lone pairs of electrons on the sulfur atom. Thus, there are two regions of electron density around sulfur.
Step 3: Apply the VSEPR Theory
VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs around an atom will arrange themselves to minimize repulsion. With two regions of electron density, the shape of SO₂ around sulfur will be linear if there are no lone pairs. However, since oxygen has lone pairs, the repulsion between these lone pairs causes a slight bending of the molecule.
Step 4: Determine the Final Geometry
Because of the lone pairs on the oxygen atoms, the two bonding pairs of electrons are pushed away from each other, resulting in a bent or V-shaped geometry with a bond angle of approximately 120°. This is not the ideal 180° of a linear molecule, but a slight bend due to the lone pair repulsion.
Conclusion
The geometry of SO₂ is bent, with a bond angle of about 120°, because of the lone pair electrons on the oxygen atoms influencing the molecular structure.