The electron domain and molecular geometry of SO3 are
A) trigonal planar, bent
B) trigonal bipyramidal, trigonal planar
C) octahedral, seesaw
D) trigonal bipyramidal, T-shaped El trigonal planar, trigonal planar
The correct answer and explanation is :
The correct answer is:
E) trigonal planar, trigonal planar
Explanation:
1. Determining the Electron Domain Geometry:
To determine the electron domain geometry of SO₃ (sulfur trioxide), we start by analyzing its Lewis structure:
- Sulfur (S) is the central atom. It has 6 valence electrons.
- Each oxygen (O) atom also has 6 valence electrons, and there are three of them.
- Total valence electrons = 6 (from S) + 3 × 6 (from O) = 24 electrons.
When drawing the Lewis structure, sulfur forms double bonds with each of the three oxygen atoms. This satisfies the octet rule for each oxygen, and sulfur uses 12 electrons (or six bonding pairs), which is acceptable because sulfur can expand its octet as it is in Period 3 of the periodic table.
Thus, there are three regions of electron density (double bonds count as one region each) around the sulfur atom. These three bonding regions will repel each other and arrange themselves as far apart as possible, resulting in a trigonal planar electron domain geometry.
2. Determining the Molecular Geometry:
In SO₃, all three electron domains are bonding pairs, and there are no lone pairs on the central sulfur atom. When there are no lone pairs, the molecular geometry is the same as the electron domain geometry.
Therefore, the molecular geometry of SO₃ is also trigonal planar.
3. Bond Angles:
In a trigonal planar geometry, the ideal bond angles are 120°, and in SO₃, the molecule is symmetrical, so all S–O bonds are equivalent and the angles are approximately 120°.
Summary:
- Electron Domain Geometry: Trigonal Planar
- Molecular Geometry: Trigonal Planar
- Correct Answer: E