Determine the molecular geometry for the following molecule: SeH₂Cl₂.

• A. T-shaped
• B. Seesaw
• C. Square pyramidal
• D. Square planar

Answer: (B)

Verified step by step guidance

1. Identify the central atom in the molecule SeH\_2Cl\_2, which is selenium (Se).
2. Determine the number of valence electrons on the central atom (Se). Selenium is in group 16, so it has 6 valence electrons.
3. Count the total number of bonding pairs around Se. There are 4 atoms bonded to Se (2 hydrogens and 2 chlorines), so 4 bonding pairs.
4. Calculate the number of lone pairs on the central atom by subtracting bonding electrons from total valence electrons: total valence electrons (6) minus electrons used in bonding (4 bonds × 2 electrons each = 8 electrons, but since each bond shares electrons, count bonding pairs as 4 pairs). Actually, for VSEPR, count electron pairs: 6 valence electrons minus 4 bonding pairs means 1 lone pair remains on Se.
5. Use the VSEPR theory to determine the electron pair geometry and molecular shape. With 4 bonding pairs and 1 lone pair, the electron geometry is trigonal bipyramidal, and the molecular geometry is seesaw.