BackUsing the VSEPR Model to Predict Molecular Geometry
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Q1. Using the VSEPR model, predict the electron-domain and molecular geometries of ClF3 and SF4.
Background
Topic: VSEPR Theory (Valence Shell Electron Pair Repulsion)
This question tests your understanding of how to use the VSEPR model to predict the shapes of molecules based on the number of bonding and non-bonding electron pairs around a central atom. ClF3 and SF4 are classic examples where lone pairs influence the molecular geometry.
Key Terms and Formulas
Electron-domain geometry: The arrangement of electron domains (bonding and lone pairs) around the central atom.
Molecular geometry: The arrangement of only the atoms (not lone pairs) in a molecule.
VSEPR Notation: ABnEm, where A = central atom, B = bonded atoms, E = lone pairs.
Step-by-Step Guidance
Count the total number of valence electrons for the central atom and the surrounding atoms in each molecule (ClF3 and SF4).
Draw the Lewis structure for each molecule, making sure to assign lone pairs to the central atom as needed.
Determine the number of electron domains (regions of electron density) around the central atom. This includes both bonding pairs (single, double, or triple bonds each count as one domain) and lone pairs.
Use the VSEPR model to identify the electron-domain geometry based on the total number of electron domains.
Determine the molecular geometry by considering only the positions of the atoms (ignore lone pairs for this step).
Try solving on your own before revealing the answer!
Final Answer:
ClF3: Electron-domain geometry is trigonal bipyramidal; molecular geometry is T-shaped. SF4: Electron-domain geometry is trigonal bipyramidal; molecular geometry is seesaw.
Both molecules have five electron domains, but the number of lone pairs determines the final shape.
