Multiple Choice
Which of the following best describes the difference between trigonal planar and trigonal pyramidal molecular geometries?
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12. Molecular Shapes & Valence Bond Theory
Molecular Geometry
Multiple Choice
What is the molecular geometry of NH_3?
A
Trigonal pyramidal
B
Trigonal planar
C
Tetrahedral
D
Bent
Verified step by step guidance1
Identify the central atom in NH_3, which is nitrogen (N).
Determine the number of valence electrons around the nitrogen atom. Nitrogen has 5 valence electrons, and each hydrogen contributes 1 electron, for a total of 8 electrons (or 4 electron pairs) around nitrogen.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the shape. The 4 electron pairs around nitrogen consist of 3 bonding pairs (with hydrogen atoms) and 1 lone pair.
According to VSEPR theory, 4 electron pairs arrange themselves in a tetrahedral electron geometry to minimize repulsion, but the presence of 1 lone pair affects the molecular shape.
Since the lone pair is not visible in the molecular shape, the molecular geometry is described by the positions of the 3 bonded atoms, resulting in a trigonal pyramidal shape.
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