Draw the lewis structure for each of the following molecules or ions, and predict their electron
Draw the lewis structure for each of the following molecules or ions, and predict their electron domain and molecules geometries: Asf3, CH+3+, BrF3, CIO3-, XeF2, BrO2
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Let’s examine the Lewis structures, electron-domain geometries, and molecular geometries of each of the given species: AsF₃, CH₃⁺, BrF₃, ClO₃⁻, XeF₂, and BrO₂.
1. AsF₃ (Arsenic trifluoride)
- Lewis Structure:
Arsenic (As) has 5 valence electrons. Each fluorine (F) contributes 7. Total: 5 + (3×7) = 26 electrons.
Three single bonds with F (6 electrons), leaving 20 electrons → 6 go on each F as lone pairs (18), remaining 2 on As as a lone pair. - Electron-Domain Geometry: Tetrahedral
- Molecular Geometry: Trigonal pyramidal
- Explanation: One lone pair on As causes a bent pyramidal shape, similar to NH₃.
2. CH₃⁺ (Methyl cation)
- Lewis Structure:
Carbon (C) has 4 valence electrons, each H has 1. For CH₃: 4 + 3 = 7, subtract 1 (positive charge) = 6 electrons.
Three C–H bonds (6 electrons). No lone pairs on carbon. - Electron-Domain Geometry: Trigonal planar
- Molecular Geometry: Trigonal planar
- Explanation: Carbon has only 3 bonding domains and no lone pair — flat triangular structure.
3. BrF₃ (Bromine trifluoride)
- Lewis Structure:
Br has 7 valence electrons, each F has 7. Total: 7 + (3×7) = 28 electrons.
Br forms 3 bonds with F (6 electrons), 3 lone pairs go to Fs (18), leaving 4 electrons → 2 lone pairs on Br. - Electron-Domain Geometry: Trigonal bipyramidal
- Molecular Geometry: T-shaped
- Explanation: Five domains (3 bonds + 2 lone pairs) give a trigonal bipyramidal EDG. Lone pairs occupy equatorial positions, leaving T-shaped geometry.
4. ClO₃⁻ (Chlorate ion)
- Lewis Structure:
Cl = 7, O = 6×3 = 18, plus 1 for negative charge → 26 electrons.
One double bond and two single bonds (with formal charges minimized). - Electron-Domain Geometry: Tetrahedral
- Molecular Geometry: Trigonal pyramidal
- Explanation: Four domains (3 bonds, 1 lone pair) result in a trigonal pyramidal shape.
5. XeF₂ (Xenon difluoride)
- Lewis Structure:
Xe = 8, F = 7×2 = 14, total = 22 electrons.
Two Xe–F bonds (4 electrons), 12 electrons on Fs, 6 on Xe → 3 lone pairs. - Electron-Domain Geometry: Trigonal bipyramidal
- Molecular Geometry: Linear
- Explanation: Lone pairs occupy equatorial positions; linear shape remains on axial bonds.
6. BrO₂ (Bromine dioxide)
- Lewis Structure:
Br = 7, O = 6×2 = 12; total = 19 electrons → odd electron species (radical).
Likely has one double bond and one single bond with Br having a lone pair and one unpaired electron. - Electron-Domain Geometry: Trigonal planar
- Molecular Geometry: Bent
- Explanation: Three electron regions (2 bonds + 1 lone pair), gives a bent structure.
Summary Table:
| Species | Electron-Domain Geometry | Molecular Geometry |
|---|---|---|
| AsF₃ | Tetrahedral | Trigonal pyramidal |
| CH₃⁺ | Trigonal planar | Trigonal planar |
| BrF₃ | Trigonal bipyramidal | T-shaped |
| ClO₃⁻ | Tetrahedral | Trigonal pyramidal |
| XeF₂ | Trigonal bipyramidal | Linear |
| BrO₂ | Trigonal planar | Bent (radical species) |
Final Notes:
The electron-domain geometry considers all electron regions (bonding and lone pairs), while the molecular geometry describes the actual shape considering only the atoms. Lone pairs distort the geometry by repelling bonded pairs more strongly than bonding pairs repel each other.