What is the molecular geometry and bond angle in H2S?
The Correct Answer and Explanation is:
Correct Answer:
- Molecular Geometry of H₂S: Bent (or V-shaped)
- Bond Angle: Approximately 92°
Explanation
Hydrogen sulfide (H₂S) is a chemical compound composed of two hydrogen atoms and one sulfur atom. To understand its molecular geometry and bond angles, we use the Valence Shell Electron Pair Repulsion (VSEPR) theory, which helps predict the shape of molecules based on electron pair repulsion.
Sulfur (S), the central atom in H₂S, is in Group 16 of the periodic table and has six valence electrons. In H₂S, it forms two single bonds with hydrogen atoms, using two of its valence electrons. This leaves four non-bonding electrons, or two lone pairs, on the sulfur atom.
According to VSEPR theory, electron pairs (bonding and non-bonding) around a central atom will arrange themselves as far apart as possible to minimize repulsion. In H₂S, there are four electron domains (2 bonding pairs + 2 lone pairs), giving it an electron geometry of tetrahedral. However, molecular geometry considers only the positions of atoms, not lone pairs. With two bonded atoms and two lone pairs, the molecular geometry is bent.
The presence of lone pairs is crucial. Lone pairs occupy more space than bonding pairs and exert stronger repulsive forces. This pushes the hydrogen atoms closer together, reducing the bond angle from the ideal tetrahedral angle of 109.5°. In H₂S, the bond angle is approximately 92°, much smaller due to the repulsion from the two lone pairs on sulfur. This is also influenced by the fact that sulfur is larger and more diffused than oxygen (in water, H₂O), which slightly affects electron cloud distribution.
In summary, H₂S has a bent molecular shape due to two lone pairs on sulfur and a bond angle of approximately 92°, explained by VSEPR theory and lone pair repulsion.
