Multiple Choice
For a molecule with the formula AB3 and no lone pairs on the central atom, what are the electron geometry and molecular geometry of the molecule?
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12. Molecular Shapes & Valence Bond Theory
Electron Geometry
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What is the electron geometry of BiI3?
A
Trigonal bipyramidal
B
Octahedral
C
Trigonal planar
D
Tetrahedral
Verified step by step guidance1
Identify the central atom in BiI\_3, which is bismuth (Bi).
Determine the number of valence electrons for bismuth. Bismuth is in group 15, so it has 5 valence electrons.
Count the number of bonding pairs and lone pairs around the central atom. BiI\_3 has three iodine atoms bonded to bismuth, so there are 3 bonding pairs. Since bismuth can expand its octet, consider any lone pairs present on Bi.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the electron geometry. The total number of electron pairs (bonding + lone pairs) around Bi determines the electron geometry. For example, 6 electron pairs correspond to an octahedral electron geometry.
Conclude the electron geometry based on the total electron pairs. If Bi has 3 bonding pairs and 3 lone pairs, the electron geometry is octahedral, even though the molecular shape might differ.
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