Multiple Choice
Which of the following correctly describes the shapes of the s and p atomic orbitals?
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12. Molecular Shapes & Valence Bond Theory
Electron Geometry
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Which of the following correctly describes the electron-pair geometry and molecular structure of ammonia (NH_3)?
A
Electron-pair geometry: tetrahedral; molecular structure: trigonal pyramidal
B
Electron-pair geometry: trigonal bipyramidal; molecular structure: seesaw
C
Electron-pair geometry: tetrahedral; molecular structure: tetrahedral
D
Electron-pair geometry: trigonal planar; molecular structure: trigonal planar
Verified step by step guidance1
Identify the central atom in ammonia (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, totaling 8 electrons or 4 electron pairs around nitrogen.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the electron-pair geometry. Four electron pairs (3 bonding pairs and 1 lone pair) arrange themselves to minimize repulsion, resulting in a tetrahedral electron-pair geometry.
Consider the effect of the lone pair on the molecular shape. The lone pair occupies one position of the tetrahedral arrangement but is not seen in the molecular shape, causing the shape to be trigonal pyramidal.
Conclude that the correct description is: electron-pair geometry is tetrahedral, and the molecular structure is trigonal pyramidal.
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