Multiple Choice
In the VSEPR theory, what is the primary factor that determines the shape of a molecule?
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12. Molecular Shapes & Valence Bond Theory
Valence Shell Electron Pair Repulsion Theory
Multiple Choice
Using the VSEPR model, what is the predicted molecular geometry of ammonia (NH_3)?
A
Trigonal planar
B
Tetrahedral
C
Bent
D
Trigonal pyramidal
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, for a total of 8 electrons (or 4 electron pairs) around nitrogen.
Use the VSEPR model to arrange these electron pairs to minimize repulsion. Four electron pairs (3 bonding pairs and 1 lone pair) around nitrogen adopt a tetrahedral electron geometry.
Recognize that the molecular geometry considers only the positions of atoms, not lone pairs. Since there is one lone pair, the shape is a trigonal pyramidal arrangement of the three hydrogen atoms around nitrogen.
Conclude that the predicted molecular geometry of NH_3 is trigonal pyramidal, not trigonal planar, tetrahedral, or bent.
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