Classify each Lewis structure given below by electron-group arrangement
The Correct Answer and Explanation is:
Please provide the Lewis structures or the chemical formulas of the molecules you want classified by electron-group arrangement. Since you haven’t yet listed any structures, I’ll give examples of common molecules and classify them by electron-group arrangement, along with a full 300-word explanation.
Examples and Classifications:
- Carbon Dioxide (CO₂)
- Lewis Structure: O=C=O
- Electron Groups on Central Atom (C): 2 (2 double bonds)
- Electron-Group Arrangement: Linear
- Boron Trifluoride (BF₃)
- Lewis Structure: B with 3 single bonds to F
- Electron Groups on Central Atom (B): 3
- Electron-Group Arrangement: Trigonal Planar
- Methane (CH₄)
- Lewis Structure: C with 4 single bonds to H
- Electron Groups on Central Atom (C): 4
- Electron-Group Arrangement: Tetrahedral
- Ammonia (NH₃)
- Lewis Structure: N with 3 single bonds to H and 1 lone pair
- Electron Groups on Central Atom (N): 4 (3 bonds + 1 lone pair)
- Electron-Group Arrangement: Tetrahedral
- Water (H₂O)
- Lewis Structure: O with 2 single bonds to H and 2 lone pairs
- Electron Groups on Central Atom (O): 4
- Electron-Group Arrangement: Tetrahedral
- Phosphorus Pentachloride (PCl₅)
- Lewis Structure: P with 5 single bonds to Cl
- Electron Groups on Central Atom (P): 5
- Electron-Group Arrangement: Trigonal Bipyramidal
- Sulfur Hexafluoride (SF₆)
- Lewis Structure: S with 6 single bonds to F
- Electron Groups on Central Atom (S): 6
- Electron-Group Arrangement: Octahedral
Explanation
Electron-group arrangement describes the geometry of regions of electron density (bonding and lone pairs) around a central atom in a molecule, according to Valence Shell Electron Pair Repulsion (VSEPR) theory. Each pair of electrons—whether in a bond (single, double, or triple) or as a lone pair—counts as one electron group.
The VSEPR model predicts that electron groups will arrange themselves to be as far apart as possible to minimize repulsion. This leads to five basic electron-group geometries:
- Linear: With 2 electron groups, the arrangement is linear (180° apart), seen in CO₂.
- Trigonal Planar: With 3 electron groups (like in BF₃), the shape is flat and triangular with 120° angles.
- Tetrahedral: With 4 electron groups (e.g., CH₄, NH₃, H₂O), the arrangement is 3D, with angles near 109.5°. Lone pairs do not change the electron-group geometry but do affect molecular shape.
- Trigonal Bipyramidal: 5 groups (e.g., PCl₅) spread out in a trigonal plane (120°) and vertical axis (90°).
- Octahedral: 6 electron groups (like in SF₆) form an 8-faced shape with 90° angles.
Understanding electron-group arrangement helps predict the molecular shape, bond angles, and polarity, which are crucial for chemical reactivity and physical properties.
