Multiple Choice
According to VSEPR theory, which of the following species has all its atoms lying in the same plane?
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12. Molecular Shapes & Valence Bond Theory
Valence Shell Electron Pair Repulsion Theory
Multiple Choice
According to VSEPR theory, what is the molecular geometry of a molecule with three bonding pairs and one lone pair on the central atom?
A
Bent
B
Tetrahedral
C
Trigonal pyramidal
D
Trigonal planar
Verified step by step guidance1
Identify the total number of electron pairs around the central atom by adding bonding pairs and lone pairs. Here, there are 3 bonding pairs and 1 lone pair, making a total of 4 electron pairs.
Recall that according to VSEPR theory, the electron pairs arrange themselves to minimize repulsion, so 4 electron pairs will adopt a tetrahedral electron geometry.
Understand that the molecular geometry depends on the positions of atoms (bonding pairs) only, while lone pairs affect the shape by repelling bonding pairs.
Since there is 1 lone pair and 3 bonding pairs, the molecular geometry is derived from a tetrahedral electron geometry but with one vertex occupied by a lone pair, resulting in a trigonal pyramidal shape.
Compare the options: 'Bent' corresponds to 2 bonding pairs and 2 lone pairs, 'Tetrahedral' corresponds to 4 bonding pairs, 'Trigonal planar' corresponds to 3 bonding pairs and 0 lone pairs, so the correct molecular geometry is 'Trigonal pyramidal'.
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